Turn Signal Troubles

[Cyamus]

New to the forum. Just picked up an 86 C30 std cab. The previous owner made a mess of the wiring (pic is what I have cut out so far). I have fixed the vast majority of it so far. I am curious if anyone has had this same problem and what the cure was. All turn signals and flashers are working properly when the headlights are off, but when I turn the headlights on the left signals are solid/wont flash. The rights work just fine though. I have printed out a complete wiring diagram and gone through all of the wiring for the lights. Was curious if maybe it could be the turn signal switch in the column shorting out or something along those lines? Any suggestions would be greatly appreciated, this is the last fix I need to get resolved in order to get it inspected and registered. Thank you in advance.

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[WP29P4A]

Check the turn signal bulbs, they should have two connections on the bottom, should be a dual filament bulb. Verify bulbs and sockets to make sure you don't have a single filament bulb in a dual filament socket. Sounds like the running lights circuit is combining/shorting with the turn signal circuit, when headlights are on. Trailer wiring is also suspect and can be miss-wired to create the situation your having. A bulb socket that has been replaced on the left side front or back would be a good place to verify switched wires that could cause the problem too.

It's possible that its the turn signal switch, but much easier to check the stuff I mentioned first, to cross the most likely off the list before you dig into the switch.

I have the same issue to fix on a 2006 Jeep next week.

 

[Cyamus]

Thank you WP29P4A, bulb was the first thing I thought too but it is the correct dual filament and both filaments are good. Wiring was suspect, but I have fixed that and verified its correct a couple of times. No trailer wiring at this time, I intentionally left that out to this point to make sure I am getting everything back to factory first.

Talking to my neighbor last night, I found out his 88 C30 does the same exact thing, so now he is curious about a fix as well.

Probably going to just order the new turn signal switch and replace it. It doesn't like to stay up for the right signal so I would probably replace it soon anyway. As well as re-check the wires under the dash... Looks like there may have been a mouse living in this truck for a while. May be a few chewed wires I haven't found yet.

 

[rusted nuts]

Bad ground is what I would be checking ,Left turn front and rear, Also left headlight. Fact that left turn comes on tells Me switch is ok.

 

[82sbshortbed]

New flasher on the fuse panel? That fixed mine.

 

[Raider L]

@Cyamus,
I came across your post about removing all this junk wiring out of your C30 and I had to laugh. I pulled a lot out of my C10 but it sure wasn't that bad. That picture is great!

 

[Big Ray]

check the connectors under the bed. Broken tabs let connectors work loose, look for corrosion and as mentioned bad grounds.
Edit: whoever invented those wire taps needs to be horsewhipped!