Description

Give your classic truck’s electrical system a dependable modern foundation with the Painless Performance 27-Circuit Classic-Plus Square Body Wiring Harness – Part #20205.

This complete chassis harness is designed for 1973–1987 full-size trucks, Blazers, and Suburbans, including C10, C20, and C30 applications. It combines vehicle-specific connections with additional circuits for modern upgrades, making it an excellent choice for restorations, custom builds, and trucks needing a complete electrical-system replacement.

Unlike a basic universal wiring kit, the Painless #20205 harness includes a factory-style bulkhead connector that mounts the fuse block in the truck’s original location. No modification to the firewall is required.

Many commonly used connectors are already installed, including connections for the headlight switch, dimmer switch, wiper motor, ignition switch, blower motor, blower switch, blower resistor, and instrument cluster. Every wire uses familiar factory-style colors and is printed with its circuit identification to make routing, installation, and future troubleshooting easier.

Included circuits

1. Air conditioning and heat
2. Accessory or cigarette lighter
3. Camper-cover light
4. Four-wheel-drive switch
5. Backup lights
6. Brake lights
7. Charging system
8. Electric fuel pump
9. Courtesy and dome lights
10. Electric-fan relay activation
11. Cruise control
12. Electric choke
13. Emergency flashers
14. Fused accessory power
15. Headlights
16. Horn relay
17. Ignition coil
18. Instrument-panel lighting and gauges
19. Parking lights
20. Radio and clock—constant and switched power
21. Power windows
22. Power door locks
23. Starting system
24. Taillights
25. Third brake light
26. Turn signals
27. Wipers and washer pump

Instrument circuits include wiring for the brake-warning light, four-wheel-drive indicator, fuel gauge, oil-pressure gauge, speakers, tachometer, and temperature gauge.

Built for restoration and customization

The harness includes a high-amperage charge wire for installing a modern high-output alternator. An included MIDI fuse protects the charging system and eliminates the traditional fusible links that can be difficult to diagnose and replace.

For trucks equipped with dual fuel tanks, the kit also includes the necessary dual-tank wiring so both tanks can continue operating through the original-style switching system.

Open-ended headlight and taillight wiring provides additional length for different grille configurations, headlight arrangements, bed lengths, Blazers, and Suburbans. The appropriate Painless light-socket pigtail kit must be purchased separately.

Available light-socket kits

• Part #30350 – 1973–1980 pickup with single round headlights
• Part #30351 – 1980–1987 pickup with single square headlights
• Part #30352 – 1980–1987 pickup with dual square headlights
• Part #30353 – 1988–1991 Suburban with dual square headlights

Important fitment information

This chassis harness does not support factory-installed throttle-body fuel injection or computer-controlled carburetors.

It also does not provide direct support for rear power glass, rear-window defrost, or rear air-conditioning and heating systems. These systems generally use wiring separate from the original chassis harness and may require additional wiring or components.

Professional installation is recommended if you are not experienced with automotive electrical systems. Always verify your truck’s year, equipment, engine-management system, headlight configuration, and accessory requirements before ordering.

Painless Performance part number: 20205