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Old 04-19-2017, 09:07 AM   #1
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Join Date: Oct 2015
Location: Kansas city
Posts: 14
1970 C10 No Brake Lights or Tail Lights

Ive been working on a friends 70 short bed. I replaced all of the wiring harness's on the truck. He did not have tail lights, brake lights and back up lights. I noticed a majority of his wiring had been cut or shorted out. So I replaced all of the harnesses, light switch, dimmer switch except the engine harness and turn signal switch. Still have issues. I replaced the brake switch under dash thats by the brake pedal. I got the the lights working last month when I unplugged the bulkhead harness and re tightened the bulkhead. Now no lights again. Ive made sure all grounds are grounded correctly and added a couple more. NOT sure whats going on. Im thinking its in the turn signal Any help or suggestions would be great.
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Old 04-19-2017, 01:17 PM   #2
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Location: Kalamazoo, Michigan
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Re: 1970 C10 No Brake Lights or Tail Lights

First of all check for power on the rear lights at the harness connector just ahead of the rear lights. This will indicate whether the wiring to the rear is good or if the problem is ahead of the harness in the cab.

The wiring for the rear lights goes through the connector plug in the firewall behind the distributor. The turn and brake lights come directly from the turn signal switch on the steering column. If the turn signals work, then the wiring for those is good and the brake lights use the same wires, so the harness is good, and the problem is in the turn signal switch or the connector.

To check the brakes, locate the white wire on the steering column connector and check it for 12 volts when you press the brake pedal. If you get 12 volts then check the yellow and dark green wires for 12 volts when you press the brake pedal.

If you get 12 volts then the TS switch is ok and the problem is in the harness wiring. It is possible for the turn signals to work, but the brakes lights may not if the connections are no good in the TS switch.

The tail lights work from a separate wire from the headlight switch. It's a brown wire, and it runs from the headlight switch to the inside of the connector, where the rest of the rear lights plug in behind the distributor.

The reverse lights' wiring runs from the fuse panel to the neutral start switch on the column (automatics) to the rear lights, through the same connector with the other wires. Check for power at the light green wires on the NSS, with the key on one of those will have power. If you jump them together and the BU lights come on then the NSS is bad or it isn't working with the column shifter. If not then the problem is in the harnes or the rear lights.

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