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27 Circuit Classic-Plus Customizable 1973-87 GM Pickup Truck Chassis Harness By Painless Performance

P/N 10205

27 Circuit Classic-Plus Customizable 1973-87 GM Pickup Truck Chassis Harness

GM Column Ignition

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Year: 1973 - 1987
Make: Chevrolet or GMC
Model: C & K Truck/SUV
Engine: Carbureted or Any Stand Alone Fuel Injection
Trans.: Any
American Made


This 27 circuit 1973-1987 GMC/Chevy harness was designed to fit the trucks, Blazers, and Suburbans. It features a factory style bulkhead connector and has many of the factory connectors already installed on the harness out of the box. Including: the headlight connectors & switch, dimmer switch, wiper motor, ignition switch, blower motor & switch, blower resistor, and instrument cluster. Each wire is custom printed with the circuit identification as well as using GM color codes for easy installation.


Number of Circuits: 27 Circuits - 18 Fuses w/ Horn Relay & Maxi Fuse
Harness Length: Factory Fitment
Fuse Type: Blade & Maxi Fuse
Firewall Passthrough: Bulkhead Connector
Color Code Based: Factory GM
Circuit Designations: Printed on Wires
Connectors Included: Ignition switch, headlight switch, dimmer swtich, wiper motor, blower switch, blower motor, blower resistor, instrument cluster and headlights, 10SI & 12 SI Alternator, HEI Power and Tach and 20 Extra 56 Series Terminals for use with any Factory GM 56 Series Connector such as Headlight Switch, Wiper Switch or A/C Switch/Blower Motor.

This harness includes circuits for: 

  1. A/C & Heat
  2. Accessory / Camper Cover Light
  3. Accessory / Cigarette Lighter
  4. Accessory / Four Wheel Drive Switch
  5. Backup Lights
  6. Brake Lights
  7. Charging
  8. Cruise Control
  9. Dome and Courtesy Lights
  10. Electric Choke
  11. Electric Fuel Pump
  12. Emergency Flashers
  13. Fan Relay Activation Power
  14. Fused Power Source
  15. Headlights
  16. Horn (Relay)
  17. Ignition Coil
  18. Instrument Panel Lighting and Gauges*
  19. Park Lights
  20. Power Door Locks
  21. Power Windows
  22. Radio/Clock (Constant and Switched)*
  23. Starting
  24. Tail Lights
  25. Third Brake Light
  26. Turn Signals
  27. Wipers and Washer Pump

* Including Wires For:
Brake Warning Light
Four Wheel Drive Light
Fuel Gauge
Oil Gauge
Temperature Gauge

 27 Circuit Classic-Plus Customizable 1973-87 GM Pickup Truck Chassis Harness By Painless Performance



ECM Flash Program



This is a basic start and run tune that we only recommend for a near stock application. We will only change the following parameters: delete VATS/PASS-KEY security, cooling fan on/off temperatures, rear end gear ratio, tire size, speed limiter, rpm limiter, idle rpm, and we will adjust the check engine light parameters. If your setup requires any other parameters tuned you will need to locate a local tuner. All ECMs are left unlocked to allow easy access for your tuner.

Step 1: Purchase one of the qualifying part numbers. See below for that list.

Step 2: If your part number is highlighted RED proceed to step 3B. If your part number is highlighted BLACK, proceed to step 3A.

Step 3A: If you have arrived at this step, your harness does not come with an ECM and you must provide one to be flashed. Please reference the manual with your harness to confirm the ECM part number required.

Step 4A: Once you have received your harness, please cut the Barcode label from the box as shown in the picture below.

Step 5A: Package and mail your ECM along with the Barcode label, a copy of your purchase receipt, and your ECM form that you are about to complete. (The address will be provided after you complete the form). We will pay for return ground shipping*. If you request a faster service, you will need to provide a return label.

Step 3B: If you have arrived at this step, your purchase comes with an ECM. You must fill out our ECM form BEFORE your purchase will ship. Proceed to Step 6.

Step 6: Click the “Start Here” button below to fill out our ECM questionnaire.

Step 7: Once we have the ECM, we will use the data from the form to flash the ECM. Then, once it has been flashed we will package the ECM and ship it back to you. If we encounter a question, we will contact you. This process can take 1-3 days.

Step 8: Once you receive your ECM, it is ready to go.


*Note: Our free return shipping is ONLY good for the lower 48 states, via ground UPS. If you are outside of those states, you must provide a return shipping label with your order. If your purchase comes with an ECM, the shipping will be covered via the retailer you purchased from.



Click the Start Here button below to get your FREE ECM Flash!

Click Here To Start The ECM Reflash Process


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