How we researched this guide
We compared 5 complete wiring kits and 2 add-on relay kits, checked 6 maker manuals and specification documents, and reviewed owner reports across 4 owner forums and build threads. Every circuit count, wire type, fuse style, and fitment claim below comes from a maker listing, a maker manual, or a linked owner source, and every pick carries its own verified Amazon link. Where a maker does not publish a figure, the guide says so rather than guessing.
Products that could not be verified on Amazon were left out, even when the brand is well known. That is why this guide has 5 picks, not a longer list padded with dealer-only kits.
The 30-second answer
For most classic truck and hot-rod rewires, buy the Painless Performance 20205 Classic-Plus 27-circuit harness if your truck is a 1973-1987 GM pickup, the Painless Performance 20112 direct-fit harness if you own a 1970-1973 Camaro, or the American Autowire Classic Update kit if you own a 1969-1972 Chevy truck and want modern fuses with factory-style fitment. For a custom build with no direct-fit kit available, the Speedway Motors Universal 22-Circuit kit is the stronger universal choice, and the Universal 21-Circuit kit is the budget universal option. Count your circuits before you buy; too few circuits is the most common rewiring mistake.
Best Overall
Painless 20205 Classic-Plus, 27 Circuits
Best if you are rewiring a 1973-1987 GM truck and want factory-style connectors already on the harness, plus room for modern accessories.
Best Direct-Fit
Painless 20112 Camaro Direct Fit, 26 Circuits
Best if you own a 1970-1973 second-generation Camaro and want a direct-fit harness split into engine, interior, and rear sections.
Best Classic Update
American Autowire Classic Update, 1969-72 Chevy Truck
Best if you own a 1969-1972 Chevy truck and want a complete Classic Update system with a modern fuse panel in the factory location.
Best Universal Value
Speedway Motors Universal 22-Circuit Kit
Best if you are building a custom car, kit car, or restomod and need a universal 22-circuit harness with labeled GXL wire.
Best Budget
Universal 21-Circuit Kit, Extra Long Wire
Best if your budget is tight and you need a universal 21-circuit kit with extra-long wires for a wide range of older vehicles.
| Kit | Circuits | Fitment | Wire and fuses | Check Price |
|---|---|---|---|---|
| Painless 20205 Classic-Plus, 27 Circuits | 27 | 1973-1987 GM truck, Blazer, Suburban | GM color codes, printed wires | Check Price |
| Painless 20112 Camaro Direct Fit, 26 Circuits | 26 | 1970-1973 Camaro | GM color codes, 3 sections | Check Price |
| American Autowire Classic Update, 1969-72 Chevy Truck | Classic Update | 1969-1972 Chevy truck | Modern ATO fuse panel | Check Price |
| Speedway Motors Universal 22-Circuit Kit | 22 | Universal, 12-volt vehicles | GXL copper, blade fuses | Check Price |
| Universal 21-Circuit Kit, Extra Long Wire | 21 | Universal, mainly 1920-1970 models | 17 fuses, extra-long wire | Check Price |
Wiring Kit Finder: How Many Circuits Does Your Build Need?
Count every powered job on your build: ignition, charging, headlights, tail lights, turn signals, horn, wipers, gauges, heater, radio, fuel pump, electric fan, power windows, power locks, and air conditioning. Enter that total below. The finder recommends a kit from this guide for that circuit count. Direct-fit kits only fit the vehicles named, so read the fitment note in the result before you buy.
Enter a circuit count to see a recommendation from this guide.
How to Choose an Automotive Wiring Kit
Five decisions separate a clean rewire from a weekend of chasing shorts. Work through them in order, and buy the circuit count and fitment your build actually needs rather than the biggest box on the shelf.
Circuit count first
List every powered job on the car, then add two spare circuits for accessories you will add later. A 12-circuit kit cannot run power windows, an electric fan, a fuel pump, and air conditioning at once. The kits here run from 21 to 27 circuits, covering most classics with modern accessories.
Direct-fit or universal
A direct-fit kit is cut, routed, and connector-matched for one vehicle family, so it installs faster and looks factory-correct. A universal kit fits almost anything but leaves every wire end open for you to cut and crimp. Choose direct-fit when one exists for your car, and universal only for custom builds or vehicles with no reproduction harness.
Wire type and labeling
Look for automotive-grade copper wire with printed circuit identification on each wire. Painless prints the circuit on its TXL wire every 12 inches, Speedway labels its GXL wire every 6 inches, and American Autowire labels its GXL wire in GM color coding. Printed, color-coded wire lets you troubleshoot the car years later without unwrapping the harness.
Fuse panel and protection
Modern blade fuses beat glass fuses for availability and for finding a blown fuse at a glance. Check whether the kit includes a headlight switch with a built-in breaker, a horn relay, and panel-mounted flashers, since those are annoying to add later. A fusible link or large main fuse on the charging feed protects the whole system if a main wire shorts.
Switches, connectors, and extras
Read the contents list before you buy. Some kits include the headlight, dimmer, and ignition switches and cluster connectors, while others expect you to reuse old switches. Factory A/C, power window, and rear defrost wiring are commonly excluded even from direct-fit kits, so confirm those three if your car has them.
Your skill level and time
A full rewire is a multi-day job, and a universal kit takes longer than a direct-fit kit because every termination is yours to make. If you have never crimped a terminal or read a diagram, a direct-fit kit with a full-color manual is the safer first project. Keep your old harness until the new one works, because it holds connectors and routing clues you may need.
Circuit Counts by Build Type
Use this table as a starting count, then adjust it for your accessory list. Every row is a planning guide, not a maker specification.
| Build type | Typical circuits | Kit that covers it | Watch out for |
|---|---|---|---|
| Basic classic, minimal accessories | 12 to 18 | Universal 21-Circuit Kit | Leaves spare capacity for later |
| Classic with fan, pump, and stereo | 19 to 21 | Universal 21-Circuit Kit | Count the fan relay separately |
| Restomod with windows and A/C | 22 | Speedway 22-Circuit Kit | A/C wiring may be separate |
| 1970-1973 Camaro restoration | 26 | Painless 20112 | Factory A/C wiring not included |
| 1973-1987 GM truck restomod | 27 | Painless 20205 | No TBI or computer-carb support |
Automotive Wiring Kits by Budget
| Tier | What you get | Example pick | Best for |
|---|---|---|---|
| Budget | Universal fit, long wires, basic fuse block | Universal 21-Circuit Kit | First rewires and tight budgets |
| Mid-range | Labeled GXL wire, switches and relays included | Speedway 22-Circuit Kit | Custom builds and kit cars |
| Direct-fit | Vehicle-matched connectors and routing | Painless 20112 or American Autowire Classic Update | Restorations that must look right |
| Maximum coverage | Highest circuit count in this guide | Painless 20205, 27 circuits | Loaded GM trucks with accessories |
Types of Automotive Wiring Kits
| Type | Pros | Cons | Best for |
|---|---|---|---|
| Direct-fit | Connectors installed, faster install | One vehicle family only | Restorations |
| Classic Update | Modern fuses, factory-style fit | Not for untouched originals | Restomods |
| Universal | Fits almost any 12-volt vehicle | Every end must be terminated | Custom builds |
| Relay and add-on kits | Fix one overloaded circuit | Not a full rewire | Headlight and fuel-pump upgrades |
Detailed Reviews of the Best Automotive Wiring Kits
Each review covers why the kit earned its award, its published specifications, fitment, owner reports, who should skip it, and what to pair it with. Anything the maker does not publish is marked as not published.
Best Overall: Painless Performance 20205 Classic-Plus Chassis Harness, 27 Circuits
Best Overall
Why the Painless 20205 Classic-Plus, 27 Circuits is our pick
The 20205 is the largest kit in this guide and the most complete one for its vehicle family. It is built for 1973-1987 GM trucks, Blazers, and Suburbans in C10, C20, and C30 form, and it uses a factory-style bulkhead connector so the fuse block mounts in the factory location. Many factory connectors arrive already installed, including headlight, dimmer, wiper, ignition, blower, and cluster connectors, cutting under-dash termination work.
Painless 20205 Classic-Plus, 27 Circuits key specs
- Part number: 20205
- Circuits: 27
- Fitment: 1973-1987 GM truck, Blazer, Suburban (C10, C20, C30)
- Wire: GM color codes, each wire printed with circuit identification
- Fuse block: mounts in factory location via factory-style bulkhead connector
- Connectors included: headlight, dimmer, wiper, ignition, blower, cluster
- Fuel injection support: not for factory TBI or computer-controlled carburetors
- Rear glass, rear defrost, rear A/C and heat: not supported, separate from OE chassis harness
- Manual: full-color instructions from Painless Performance
- Warranty: chassis harnesses covered under lifetime warranty per Painless warranty statement
- Made for: trucks with power accessories and modern upgrades
Painless 20205 Classic-Plus, 27 Circuits: fits and best for
This kit fits 1973-1987 Chevrolet and GMC full-size trucks, Blazers, and Suburbans, whether C10, C20, or C30. It is best for a truck restomod adding power windows, air conditioning, an electric fan, or a fuel pump, since 27 circuits leave room for those accessories. It is not for a factory-original restoration, nor for a truck running factory TBI fuel injection, which the maker explicitly excludes.
Painless 20205 Classic-Plus, 27 Circuits pros and watch-outs
- 27 circuits, the most in this guide
- Factory-style bulkhead connector and factory fuse-block location
- Many factory connectors pre-installed
- Printed wires in GM color codes
- Lifetime warranty on chassis harnesses
- Does not support factory TBI or computer-controlled carburetors
- No rear power glass, rear defrost, or rear A/C and heat support
- GM trucks only, not a universal kit
- Large kit that still needs a full weekend to install
Painless 20205 Classic-Plus, 27 Circuits: what owners report
Owners rewiring square-body GM trucks describe the Classic-Plus instructions as the part that makes the job manageable, with printed wires and GM color codes doing most identification work. Forum threads praise the factory-location fuse block for keeping the under-dash area tidy, and caution buyers to confirm exclusions such as TBI support before ordering.
Painless 20205 Classic-Plus, 27 Circuits: who should not buy
Do not buy this kit if your truck runs factory TBI fuel injection or a computer-controlled carburetor, or if your truck is not a 1973-1987 GM model. A better alternative for a non-GM custom build is the Speedway Motors Universal 22-Circuit Kit in this guide, and for a 1969-1972 Chevy truck the American Autowire Classic Update kit is the closer match.
Painless 20205 Classic-Plus, 27 Circuits: pair it with
Pair it with the Painless Performance 50102 Fuel Pump Relay Kit, which adds a dedicated 30-amp relay circuit for an electric fuel pump instead of loading the pump onto an existing circuit. The relay kit link is directly below.
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Tip: before you unwrap anything, lay the harness on the floor and label each branch with masking tape for its destination. See our guide to automotive fuse pullers for the tool that makes fuse testing painless.
Best Direct-Fit Kit: Painless Performance 20112 Direct Fit Camaro Harness, 1970-1973, 26 Circuits
Best Direct-Fit
Why the Painless 20112 Camaro Direct Fit, 26 Circuits is our pick
The 20112 is the only direct-fit Camaro kit in this guide, and it is the right pick for a second-generation Camaro because it arrives split into three sections, engine, interior, and rear, with virtually every connector installed out of the box. A fully integrated ground circuit is built in, with a 6-gauge charge wire and a 150-amp midi fuse for modern alternators and fans. The 150-plus page full-color manual is the most detailed documentation of any kit here.
Painless 20112 Camaro Direct Fit, 26 Circuits key specs
- Part number: 20112
- Circuits: 26
- Fitment: 1970-1973 second-generation Camaro
- Sections: engine, interior, and rear, three separate sections
- Ground circuit: fully integrated ground circuit
- Charge wire: 6-gauge charge wire
- Main fuse: 150-amp midi fuse
- Manual: 150-plus page full-color step-by-step manual available
- Wire: custom printed with circuit identification, GM color codes
- Factory A/C wiring: not included, power wire for A/C switch included
- Power window and lock wiring: not included, part 30715 sold separately
- Warranty: chassis harnesses covered under lifetime warranty per Painless warranty statement
Painless 20112 Camaro Direct Fit, 26 Circuits: fits and best for
This kit fits 1970-1973 second-generation Camaros only. It is best for a Camaro restoration or restomod wanting a factory-correct layout with modern protection. It is not for any other GM car, nor for a Camaro whose factory A/C wiring must be replaced in the same job, since the maker states that factory A/C wiring is not included.
Painless 20112 Camaro Direct Fit, 26 Circuits pros and watch-outs
- Direct fit for 1970-1973 Camaros, connectors pre-installed
- Three-section layout keeps routing organized
- 6-gauge charge wire and 150-amp midi fuse upgrades
- 150-plus page full-color manual
- Integrated ground circuit
- Factory A/C wiring not included
- Power window and lock wiring sold separately as part 30715
- Camaro-only fitment
- Long manual means a long install, plan a full weekend
Painless 20112 Camaro Direct Fit, 26 Circuits: what owners report
Camaro owners praise the three-section split, since engine, interior, and rear sections can be routed and checked independently. The recurring caution matches the maker note: factory A/C wiring is a separate job, so owners who need it order that harness alongside this kit.
Painless 20112 Camaro Direct Fit, 26 Circuits: who should not buy
Do not buy this kit if your car is not a 1970-1973 Camaro, or if you need factory A/C wiring replaced in the same project without buying a second harness. For a universal custom build, the Speedway Motors Universal 22-Circuit Kit is the better alternative, and for a GM truck the Painless 20205 is the matching direct-fit choice.
Painless 20112 Camaro Direct Fit, 26 Circuits: pair it with
Pair it with the Painless Performance 30802 High Beam Headlight Relay Kit if your Camaro runs four headlights, since it keeps all four lights on in high-beam mode with a heavy-duty 40-amp relay. The relay kit link is directly below.
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Tip: photograph your original harness routing before you remove a single wire, especially around the firewall and rear body. See our wiring-kit comparison guide for how direct-fit and universal kits differ.
Best Classic Update Kit: American Autowire Classic Update Complete Wiring Kit, Chevy Truck 1969-72
Best Classic Update
Why the American Autowire Classic Update, 1969-72 Chevy Truck is our pick
American Autowire is the other great American name in classic wiring, and its Classic Update line is built for modified cars and trucks that need modern protection without giving up factory-style fitment. The 1969-1972 Chevy truck kit is a complete headlight-to-taillight system with a modern ATO fuse panel designed to fit the original location with no firewall modifications. That full-function design is exactly what a truck adding EFI, digital gauges, or Vintage Air needs.
American Autowire Classic Update, 1969-72 Chevy Truck key specs
- Product line: American Autowire Classic Update Series
- Fitment: Chevy Truck 1969-72, complete kit
- Fuse panel: modern ATO-style fuse panel, fits original location
- Headlight switch: replacement switch with internal 25-amp circuit breaker included
- Relays: standard turn signal flasher, hazard flasher, and horn relay mounted on harness
- Hardware: all required mounting hardware supplied
- Instrument cluster: cluster harness disconnect system for easy service
- Engine feeds: coil, tach, water temperature, oil pressure, electric choke, electric speedometer
- Rear body: rear body harness plugs into main harness at bulkhead disconnect
- Wire: modern GXL wire in GM color coding
- Instructions: full-color schematics and instructions included
- Accessory support: gauge packages, wiper systems, heat and A/C systems
American Autowire Classic Update, 1969-72 Chevy Truck: fits and best for
This kit fits 1969-1972 Chevrolet trucks as a complete rewiring system. It is best for a truck being modernized with EFI, Dakota Digital gauges, Vintage Air, or similar accessories, since the design leaves room for those additions. It is not for a concours restoration that must reproduce the original harness exactly; the Factory Fit line serves that goal instead.
American Autowire Classic Update, 1969-72 Chevy Truck pros and watch-outs
- Complete headlight-to-taillight system
- Modern ATO fuse panel in the factory location
- Headlight switch with 25-amp breaker included
- Cluster disconnect system for easy service
- Built for EFI, digital gauges, and A/C additions
- Not an exact original-reproduction harness
- Part number not stated in the listing excerpt reviewed
- Truck-specific, not universal
- Modern accessories may still need their own add-on harnesses
American Autowire Classic Update, 1969-72 Chevy Truck: what owners report
Truck owners on classic forums describe the Classic Update install as the moment their truck stopped having electrical gremlins, crediting the factory-location panel and labeled wires. The recurring advice is to list planned accessories before ordering, as American Autowire itself advises, rather than discovering a missing circuit after the harness is in.
American Autowire Classic Update, 1969-72 Chevy Truck: who should not buy
Do not buy this kit if your truck is not a 1969-1972 Chevy truck, or if your goal is an exact factory-original reproduction. For an untouched original, look at a Factory Fit reproduction instead, and for a custom build with no Classic Update kit available, the Speedway Motors Universal 22-Circuit Kit in this guide is the alternative.
American Autowire Classic Update, 1969-72 Chevy Truck: pair it with
Pair it with the Painless Performance 50102 Fuel Pump Relay Kit when you add an electric fuel pump, so the pump gets its own 30-amp relay circuit rather than sharing a general accessory feed. The relay kit link is directly below.
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Tip: write your accessory wish list before you order, including EFI, gauges, and A/C, and check each one against the kit contents. See our beginner wiring-kit guide for a slower walkthrough of that list.
Best Universal Value: Speedway Motors Universal 22-Circuit Wiring Harness Kit
Best Universal Value
Why the Speedway Motors Universal 22-Circuit Kit is our pick
The Speedway Motors 22-circuit kit is the strongest universal pick in this guide because it balances circuit count, wire quality, and documentation. It is a universal design for nearly any 12-volt vehicle and engine combination, with 22 individually fused circuits in 11 quick-start sections. The wire is GXL polyethylene-insulated copper, color-coded and labeled every 6 inches, and the kit is plug-and-play with 1968-1996 GM tilt columns. The installed kit weighs under 8 pounds.
Speedway Motors Universal 22-Circuit Kit key specs
- Part number: 910-64022
- Circuits: 22 individually fused circuits
- Sections: 11 quick-start sections
- Fitment: universal, nearly any 12-volt vehicle and engine combination
- Steering column: plug-and-play with 1968-1996 GM tilt columns
- Wire: GXL polyethylene-insulated automotive-grade copper
- Labeling: color-coded, labeled every 6 inches
- Included: headlight switch, dimmer switch, horn relay, accessory wiring
- Installed weight: under 8 pounds
- Instructions: complete instructions and diagrams included
- Use cases: classic vehicles, kit cars, replicas, race cars
- Certification: Intertek certification number TE-00325098 on listing
Speedway Motors Universal 22-Circuit Kit: fits and best for
This kit fits nearly any 12-volt vehicle, including classic cars, kit cars, replicas, and race cars that need extra accessory circuits beyond ignition, lighting, horn, wipers, gauges, and A/C and heat. It is best for a custom build, an engine swap, or a vehicle with no reproduction harness available. It is not the fastest install here, since universal means every wire end is yours to cut and terminate.
Speedway Motors Universal 22-Circuit Kit pros and watch-outs
- 22 circuits with room for accessories
- GXL copper wire, labeled every 6 inches
- GM tilt-column plug-and-play
- Headlight and dimmer switches included
- Under 8 pounds installed
- Universal install takes longer than direct-fit
- Every wire end must be cut and terminated
- Not vehicle-specific, no pre-installed vehicle connectors
- Column fitment is GM tilt, other columns need the pin-out diagram
Speedway Motors Universal 22-Circuit Kit: what owners report
Owners rewiring shoebox Fords and other customs report that the 11 quick-start sections keep the job organized, one branch at a time. The recurring caution is that a universal harness rewards patience: rushed terminations create the same intermittent faults the builder was escaping, while careful crimps produce a reliable system.
Speedway Motors Universal 22-Circuit Kit: who should not buy
Do not buy this kit if a direct-fit kit exists for your vehicle and you want the fastest install, because a direct-fit harness will save you hours of termination work. For a 1970-1973 Camaro or a 1973-1987 GM truck, the matching Painless kit in this guide is the better buy.
Speedway Motors Universal 22-Circuit Kit: pair it with
Pair it with the Painless Performance 30802 High Beam Headlight Relay Kit if your build runs four headlights, since the 40-amp relay takes headlight load off the switch. The relay kit link is directly below.
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Tip: terminate one quick-start section completely, then test it, before moving to the next section. See our professional wiring-kit guide for the full section-by-section method.
Best Budget Universal Kit: Universal 21-Circuit Wiring Harness Kit, Extra Long Wire
Best Budget
Why the Universal 21-Circuit Kit, Extra Long Wire is our pick
The Universal 21-Circuit Kit is the budget pick because it covers the essentials at the lowest cost in this guide: 21 circuits, 17 fuses, and extra-long wires that fit almost any vehicle, with compatibility focused on model years mainly from 1920 to 1970 and on GM, Ford, Chrysler, Dodge, and Mopar builds. The kit includes circuits for wipers, radio, cruise, heater and air, clock, dome light, power doors, power seats, fan power, coil, choke, instruments, flashers, fuel pump power, brakes, power windows, headlights, and horn. For a first rewire on a simple classic, that list is complete enough to finish the car.
Universal 21-Circuit Kit, Extra Long Wire key specs
- Circuits: 21
- Fuses: 17
- Wire: extra-long wires for a wide range of vehicles
- Compatibility: GM, Chevy, Chrysler, Dodge, Ford, Mopar, Mercury, Plymouth, Oldsmobile, GMC
- Model years: mainly 1920-1970
- Circuits included: wipers, radio, heater and air, dome, power doors, power seats, fan, coil, choke, instruments, flashers, fuel pump, brakes, power windows, headlights, horn
- Type: universal, not vehicle-specific
- Brand note: generic universal listing, not a named maker harness
- Instructions: instructions included per listing
- Best for: hot rods, rat rods, and simple classics
- Part number: not published on the listing excerpt reviewed
- Fitment check: confirm column connectors before ordering
Universal 21-Circuit Kit, Extra Long Wire: fits and best for
This kit fits almost any older vehicle, with its widest compatibility on 1920-1970 GM, Ford, and Mopar builds. It is best for a budget rewire of a simple classic, hot rod, or rat rod where the circuit list above covers everything on the car. It is not for a complex restomod with EFI, digital gauges, and multiple power accessories, since 21 circuits with 17 fuses leave less spare capacity than the 22- and 27-circuit kits.
Universal 21-Circuit Kit, Extra Long Wire pros and watch-outs
- 21 circuits at the lowest cost in this guide
- Extra-long wires fit wide vehicles
- Broad 1920-1970 compatibility
- Covers fan, fuel pump, windows, and A/C basics
- Good first-kit circuit list
- Generic listing, not a named maker harness
- 17 fuses for 21 circuits, so some circuits share protection
- No named maker manual or warranty statement found
- Less spare capacity than the 22- and 27-circuit kits
Universal 21-Circuit Kit, Extra Long Wire: what owners report
Owners of budget universal kits report that the extra-long wires save the job, since short wires force splices in awkward places. The recurring caution is to verify the column connectors and fuse-block layout on arrival, before cutting anything, since a generic kit will not match any one vehicle perfectly.
Universal 21-Circuit Kit, Extra Long Wire: who should not buy
Do not buy this kit if your build needs more than 21 circuits, runs EFI with its own harness requirements, or must look factory-correct for judging. For a loaded restomod, the Speedway 22-Circuit Kit is the next step up, and for a vehicle with a direct-fit kit available, the matching Painless or American Autowire kit is the better buy.
Universal 21-Circuit Kit, Extra Long Wire: pair it with
Pair it with the Painless Performance 50102 Fuel Pump Relay Kit so an electric fuel pump gets its own 30-amp relay circuit instead of sharing a fuse with other accessories. The relay kit link is directly below.
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Tip: check the column connectors and fuse-block layout against your car before you cut the first wire. See our wiring-kits-versus-tools guide for the tools that make a budget install go smoothly.
Spec Comparison
| Spec | Painless 20205 | Painless 20112 | AAW Classic Update |
|---|---|---|---|
| Circuits | 27 | 26 | Classic Update |
| Fitment | 1973-87 GM truck | 1970-73 Camaro | 1969-72 Chevy truck |
| Wire | GM codes, printed | GM codes, printed | GXL, GM codes |
| Fuse style | Factory location | Modern panel | ATO panel |
| Switches included | Headlight, dimmer, wiper, ignition | Not stated separately | Headlight switch, flashers, horn relay |
| Manual | Full-color | 150-plus page color | Full-color schematics |
| Ground circuit | Not stated | Fully integrated | Not stated |
| Main protection | Not stated | 150-amp midi fuse | Not stated |
| Warranty | Lifetime, chassis | Lifetime, chassis | Not published |
| Check Price | Check Price | Check Price | Check Price |
| Spec | Speedway 22 | Universal 21 |
|---|---|---|
| Circuits | 22 | 21 |
| Fitment | Universal 12-volt | Universal, 1920-70 |
| Wire | GXL, labeled 6 in | Extra-long wire |
| Fuse style | Blade fuses | 17 fuses |
| Switches included | Headlight, dimmer, horn relay | Not stated |
| Manual | Instructions included | Instructions included |
| Ground circuit | Not stated | Not stated |
| Main protection | Not stated | Not stated |
| Warranty | Not published | Not published |
| Check Price | Check Price | Check Price |
No score row is given here, because circuit count alone does not rank a harness. Fitment, spare capacity, and manual quality matter more, and those are covered above.
Installation and Wiring Basics
Start by disconnecting the battery and photographing the original routing, then remove the old harness in sections and label every connector you plan to reuse. Mount the fuse panel first where the maker specifies, route branches loosely before crimping anything, and work one section at a time, engine, dash, then rear, checking each section with a multimeter before moving on.
Grounds deserve as much attention as power wires. Run a dedicated ground from battery to body and body to engine, clean every ground point to bare metal, and never rely on a rusty bolt or painted bracket. Use the correct crimp tool, tug-test every crimp, protect every wire through sheet metal with a grommet, and keep high-current wires away from sharp edges and exhaust heat. For tool choices, see our guides to automotive multimeters under 100, automotive fuse pullers, and fastener assortments for the hardware that keeps a harness tidy.
Safety Essentials
- Disconnect the battery before you touch any harness, and keep the negative cable off until the new harness is fully routed.
- Never replace a fuse with a higher rating to stop it blowing; a blowing fuse is telling you about a short, not asking for a bigger fuse.
- Protect every wire through sheet metal with a grommet, and never let a live wire rest on a sharp edge or an exhaust manifold.
- Fuse the alternator charge wire and any direct battery feed, and keep a fire extinguisher within reach during first power-up.
- Do not power the car until every ground is cleaned to bare metal and tightened, because a bad ground causes dim lights, hot wires, and false diagnoses.
- If any wire smells hot, smokes, or melts insulation during testing, disconnect the battery immediately and find the short before trying again.
Three add-on picks that make a rewire safer: the Painless 50102 Fuel Pump Relay Kit, with a 30-amp relay and circuit breaker for an electric fuel pump; the Painless 30802 High Beam Headlight Relay Kit, with a 40-amp relay that takes headlight load off the switch; and our fuse-puller guide, which covers the tool for safe fuse testing without pliers on a live panel.
For fuse testing tools, see our automotive fuse puller guide.
Troubleshooting
| Symptom | Likely cause | Fix |
|---|---|---|
| Fuse blows immediately | Short to ground on that circuit | Disconnect loads one at a time, inspect wire routing |
| Dim headlights | Weak ground or overloaded switch | Clean grounds, add a headlight relay kit |
| Gauges read wrong | Wrong sender wire or bad ground | Check cluster ground and sender connections |
| Fuel pump will not run | No relay feed or blown fuse | Check relay kit wiring and pump fuse |
| Intermittent accessories | Loose crimp or terminal | Tug-test crimps, re-crimp any loose terminal |
| Battery drains overnight | Circuit staying live | Test for draw with a multimeter, find the live feed |
Who Should NOT Buy These Wiring Kits
Owners of untouched originals should not buy these kits. If your car must keep its original harness for judging, a modernized or universal harness changes the car. Keep the original harness, repair it section by section, and protect the car with our classic car cover guide while it sits.
Owners of modern CAN-bus cars should not buy these kits. These harnesses are built for 12-volt classic and custom cars, not for computer-networked modern vehicles where a harness swap can disable modules. For a modern car with an electrical fault, diagnose the fault first with our multimeter guide and our alternator tester guide.
Builders who want a one-hour job should not buy these kits. A full rewire takes days, not hours, and a universal kit takes longer than a direct-fit kit. If you only need one circuit fixed, buy the matching relay kit or book a shop, rather than starting a full rewire you cannot finish.
Buyers without a circuit list should not order yet. Count your circuits first with the finder above, then order. An unordered kit that arrives with too few circuits costs you a return and a second install weekend.
Final Verdict
Best Overall to the Painless 20205 Classic-Plus, 27 Circuits: Check Price
Best Direct-Fit Kit to the Painless 20112 Camaro Direct Fit, 26 Circuits: Check Price
Best Classic Update Kit to the American Autowire Classic Update, 1969-72 Chevy Truck: Check Price
Best Universal Value to the Speedway Motors Universal 22-Circuit Kit: Check Price
Best Budget Universal Kit to the Universal 21-Circuit Kit, Extra Long Wire: Check Price
For a 1973-1987 GM truck, the Painless 20205 is the pick. For a 1970-1973 Camaro, the Painless 20112. For a 1969-1972 Chevy truck, the American Autowire Classic Update kit. For any other classic or custom build, the Speedway 22-Circuit Kit is the stronger universal choice, and the Universal 21-Circuit Kit is the budget way in.
FAQ
How many circuits do I need for a classic car rewire?
Count every powered job on the car, including ignition, charging, headlights, tail lights, turn signals, horn, wipers, gauges, heater, radio, fuel pump, electric fan, power windows, and air conditioning, then add two spares. Most simple classics land between 12 and 18 circuits, while a loaded restomod with windows, fan, pump, and A/C lands between 21 and 27. Buying the circuit count your list produces is the best way to avoid a second install.
Is a direct-fit kit better than a universal kit?
A direct-fit kit is better when one exists for your vehicle, because its connectors, routing, and lengths are matched to that car and it installs faster. A universal kit is better when no direct-fit kit exists, for custom builds, kit cars, and engine swaps, because it can be adapted to almost any 12-volt vehicle. The trade-off is time: a universal kit leaves every wire end open for you to cut and crimp.
Can I install a wiring kit myself?
Yes, if you can read a wiring diagram, crimp terminals cleanly, and set aside several days. A direct-fit kit with a full-color manual is the most beginner-friendly first project, while a universal kit suits builders who have done at least one smaller wiring job. Keep your old harness until the new one works, test each section as you finish it, and have a shop check any circuit that behaves strangely.
Do these kits support fuel injection?
It depends on the kit and the injection system. The Painless 20205 explicitly does not support factory TBI fuel injection or computer-controlled carburetors, while American Autowire Classic Update kits are designed with standalone EFI additions in mind. Always check the maker note for your exact injection system before ordering.
What wire type should a good kit use?
Look for automotive-grade copper wire with the circuit printed on it, such as TXL wire from Painless or GXL wire from Speedway and American Autowire. Printed, color-coded wire makes troubleshooting possible years later without unwrapping the harness. Avoid kits that do not state their wire type, and never reuse brittle original wire alongside a new harness.
Do I need relay kits with a new harness?
You need a relay kit whenever one switch or circuit would otherwise carry a heavy load, most commonly headlights and electric fuel pumps. The Painless 30802 headlight relay kit and the 50102 fuel pump relay kit in this guide take those loads off the switch and onto a dedicated relay circuit. Adding relays during the rewire is far easier than adding them later.
How long does a full rewire take?
Plan a full weekend at minimum, and a week of evenings for a universal kit on a complex car. Direct-fit kits are faster because connectors arrive installed, while universal kits add hours of cutting and crimping. Rushing causes most rewire faults, so work one section at a time and test each section.
Will a new harness fix my electrical gremlins?
A new harness fixes gremlins caused by corroded wire, cracked insulation, and overloaded circuits, which are the most common causes on old cars. It will not fix a bad alternator, failing switch, or faulty sender, so test those parts before blaming the harness.
What is not included in most wiring kits?
Factory air conditioning wiring, power window and lock wiring, and rear defrost wiring are commonly excluded even from direct-fit kits, so check the contents list for those three before ordering. Switches are also sometimes excluded, with some kits including the headlight and dimmer switches and others expecting you to reuse your old ones. Reading the contents list before you buy prevents the most common surprise.
Sources & changelog
Manufacturer and maker sources:
- Painless Performance 20205 Classic-Plus Chassis Harness, Amazon listing
- Painless Performance 20112 Camaro Direct Fit Harness, Amazon listing
- American Autowire Classic Update Chevy Truck 1969-72, Amazon listing
- Speedway Motors Universal 22-Circuit Wiring Harness, Amazon listing
- Universal 21-Circuit Wiring Harness Kit, Amazon listing
- Painless Performance 50102 Fuel Pump Relay Kit, Amazon listing
- Painless Performance 30802 Headlight Relay Kit, Amazon listing
- Painless 10101-10104 Classic Customizable Harness Manual 90625
- Speedway Motors Wiring Kit Instructions
- American Autowire: Need Help Deciding, product lines explained
- Hot Rod: American Autowire Harness Wiring Options for C10s
- In the Garage Media: Highway 22 Plus install on a 1948 Chevy pickup
- Chevy Hardcore: Muscle Car Wiring Harness Updates with Ron Francis Wiring
- Classic Parts: Classic Update Kit features, 1947-54 trucks
Owner and community sources:
- ClassicBroncos forum: wiring kits discussion
- IH8MUD forum: Best wiring harness discussion
- IH Parts America forum: Scout II rewire thread
- For A Bodies Only forum: aftermarket wiring discussion
- CJ Pony Parts: Painless Performance background
- THMotorsports: Painless Wiring background
Changelog — October 31, 2026: guide first published.
By Leo, Founder, WinchInsider
Leo founded WinchInsider to give classic car and truck owners research-based buying guides built from maker documents and owner reports, with no invented specifications.
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Browse the full category: Automotive Wiring Kits and Classic Cars and Restoration.
For battery care alongside a rewire, see our battery maintainers and jump starters guide, our LED headlight bulbs guide, our automotive degreasers guide, and our overlanding tool kits guide.
Top pick: Painless 20205 Classic-Plus, 27 Circuits