Turn Signals/Hazards '68 C10

[wd 69]

Wondering if anybody can help. When I use my turn signals, I get my hazard lights. The hazards themselves work independently, but the turn signals activate the hazards. Both front and back are lit and flashing, although the directional that should be on is slightly brighter than the one that should be off. I suppose these two circuits must be shorted somewhere, and my guess (hope I'm wrong) is that since the hazard switch only brings in the hazards - but the turn signal brings in both. . . it's more than likely in the turn signal switch in the column.
Any simpler suggestions I might start with? Thanks!

[VetteVet]

The hazard wire is the brown wire in the middle of the column harness. It is powered all the time when the battery is connected. The purple wire next to it is the turn signal power wire. It is powered only when the key switch is on.

Disconnect the column connector and set aside the part that goes to the column.
Check the two wires for power with the key off and then with the key on. If the purple wire has power with the key off then it is shorted to the brown wire or to another 12 volt source and the turn signals will work with the key off. If it doesn't then the short is most likely in the turn signal switch and is between the four light points.

You can check this by using your multimeter to check for continuity between the yellow and dark green wires and the light blue) and dark blue wires These are the four wires that feed the turn signals. The four light wires are-- yellow (left rear) light blue (left front) and dark green (right rear ) and dark blue (right front).

You should only get continuity between the two left side wires or the two right side wires when you select the left turn or the right turn signal. You won't need power to check these
for continuity. If you get continuity between the two sides when you select left or right then you have a bad switch.

[wd 69]

Thanks for the response. I really appreciate the info, especially the help identifiying which wire is which. The turn signals don't work when the key is off, so it makes sense that the two circuits wouldn't be shorted - must be in the turn signal switch as you described. Thanks again for your help.

[wd 69]

Well, here is something else I noticed: When I pull out the light switch, I get both elements lit in the tail light bulbs. Same thing when I step on the brake (with the lights off). So when I break with the lights on - nothing gets brighter. Obviously, I should have the two elements separate. One for brakes and blinkers, and one for tail lights. I got under the bed and pulled the plug in the wiring harness running back toward the cab and rang them out. Everything looked shorted. Went up under the dash and pulled the semi-circular plug there. Rang it out.
The female end runs back to the tail lights, right? If I am right about that - it did ring shorted. Thing is, I went back to the plug under the bed and even after breaking the connection (semi-circular plug) under the dash - the plug under the bed by the spare still rang shorted. Circuit must be shorted in the harness under the bed then, right?

[VetteVet]

I tend to agree with you. If you can separate the connector on the firewall behind the distributor and run a continuity check between the brown and yellow and the brown and dark green wires in the two halves of the connector, it will tell you which section of the harness the short is in.

I'm betting you see continuity in the section that goes under the truck. If so then disconnect the frame connector in the middle of the truck. if you still have continuity then the short is in that section, if not then it's further back. Plug in the mod frame section then disconnect the rear section. If it goes away then the short is in the rear section.

There is a rare event that happens but it will cause your symptoms.
the filaments in one of the bulbs burns in two and one of the burnt sections falls into the other filament, connecting the tail light and brake light.

[wd 69]

Problem Solved! Got the truck up in the air and found that all four wires were burned to a crisp. . . right beside the muffler. Spliced in new wires, one at a time, and was back in business. Thanks again for your help!

[tdangle]

Glad you figured it out. Usually it's a simple thing, like damaged wiring. I once helped a neighbor who had a similar problem with lighting and all it was was a shorted bulb. The filament for the brake light had broken and was shorting to the running light filament. 1st rule look for the obvious.