Wiring

[dfitch1]

Good morning, I am new to this site. I just purchased a 67 c/10 and i cant wait to get started. I've always wanted to restore an old chevy pickup and I'm looking forward to this project. My question is about the tail lights. Last night i got the lights to work. But when I hit the brake pedal, the fuse blows and i noticed that the turn signals dont work either, in the cab and at the tail light. Any help or reference would be great. I will also be picking up a 67-72 service manual in the near future. Thank you for any help!

[VetteVet]

Welcome to the forums. Your problem is common on these old trucks.

The brakes and turn signals are integrated from the turn signal switch to the rear of the truck. They use the same bulb filaments and the same wires.

to isolate the short, un plug the steering column connector and try the brakes with a new fuse. If it blows then the short is in the turn signal switch or in the wiring from the brake switch.
A member just had the same problem and his brake switch was shorted to ground.

If your turn signals cause the fuse to blow as well as the brakes then you have a short to ground between the turn signal switch and the rear of the truck. It may be in the TS switch or the wiring to the rear of the truck. Possibly in the socket itself. In either the left or right wire or socket.

Install a new fuse and try the left turn signal then the right. Take note of which side blows the fuse or if neither side blows.

The yellow wire is for the left turn/brake light and the dark green wire is for the right turn/brake side.

Try these tests and get back with us with the results.

[dfitch1]

Thank you! I will try these tests and get back to you.

[dfitch1]

Ok, here's the deal. I found a wiring harness plug at the rear of the truck that branches off to the taillights .I unpluged the taillights basically eliminating them. With the truck running, i tried the turn signals, fuse is good. The moment i hit the brake pedal, blown fuse.

[michael bustamante]

Prob a bad brake switch or a short in the wiring along the left frame rail. Follow it and look for cuts groinding or exposed wiring

[dfitch1]

Ok , i will unplug the switch and test the wiring plug to ground.

[dfitch1]

On the plug is a white wire and a orange wire. Do you know what i should be reading with my meter?

[VetteVet]

On the plug is a white wire and a orange wire. Do you know what i should be reading with my meter?

You should read 12 volts on the orange wire and nothing on the white wire. With your meter on resistance, check for resistance between the white wire and a good ground. You should get very high resistance to infinity, or no reading. If you get low resistance to zero ohms then the white wire is shorted to ground.



The orange wire is hot from the fuse panel and the white wire runs to the steering column connector and up the column to the turn signal switch. You need to unplug the connector and apply the brakes. If the fuse blows then the short is between the brake switch and the connector.

if it doesn't blow then the short is between the connector and the turn signal, probably grounded in the column or the turn signal switch.

The white wire carries power to the turn signal switch which connects it to the yellow and dark green wires that are the brake/ turn light wires.

If the fuse didn't blow with the connector unplugged, Plug it back in and unplug the rear light connector on the firewall just behind the distributor and throttle mount. Try the brakes and check the fuse. If it blows the short is in the cab wiring or in the turn signal switch or in the column.

If it doesn't blow then the short is in the harness from the firewall connector to the rear lights. it runs underneath the cab and bed along the left frame rail to the rear lights and there should be another connector in the harness about midway.

[dfitch1]

Ok just to be clear, their are 3 plugs on the lower part the the steering colume. One connector has a orange and white wire. The second has a light green and dark green wire. The third has 2 purples. Are these the wires you are referring to?

[dfitch1]

Originally Posted by dfitch1

Ok just to be clear, their are 3 plugs on the lower part the the steering colume. One connector has a orange and white wire. The second has a light green and dark green wire. The third has 2 purples. Are these the wires you are referring to?

The plug with the orange and white goes to the brake pedal switch. I pluged the orange/white connector back in and unpluged at the fire wall and hit the brake and the fuse blew. Unplugging the orange /white connector from the colume and pressing the brake, the fuse is good.

[truckdude239]

there should be a connecter in a half moon shape with about 6-7 wires i believe in it that is the turn sigal switch it might be a flat long plug witha moon shape adapter

[dfitch1]

Yep, I saw the half moon piece where the 3 connectors plug in. I know their are wires going up inside to the turn signal. I just have to figure out how to get the colume apart to see if the wire is shorted. Unless the half moon piece is bad?

[4oldcars]

half moon = neutral saftey switch