Chevy Turn Signal Problem...

ChromolyKid

Well-Known Member
Alright, here's one for you electrical wizards on here. I've got a 1990 C1500 Chevy, and I recently noticed a big problem. My turn signals work fine, front and rear, both running lights and turn lights flash. BUT, when I turn my running lights or headlights (which includes running lights) on, I can no longer signal. No blink out of any lights. What could the problem be? Blown fuse somewhere? Has a relay somewhere fried? Or is there a loose connection somewhere in the maze of wires? Any help would be greatly appreciated, I'm not driving at night until that's fixed. Thanks.
 

ChromolyKid

Well-Known Member
Anybody? :confused: I really need to get this fixed. I checked all the fuses and these are the conditions under which the problem occurs:
1. When the running lights and/or the headlights are on, the turn signals will not function.
2. When I pull the turn signal fuse out, the turn signals will not work (this is just to reassure that the signals are wired properly through the fuse box)
3. When I pull the light fuse out, neither the head nor running lights work (same reason as 2)
4. If I step on the brake, and signal without any of the lights on, it works fine.
5. While the lights ARE on, if I try to signal, the rear light will light up for a split second like it's attempting to flash, but won't. Nothing from the front.
6. Not sure if it's anything significant to the problem, but the running light signal isn't nearly as bright as when it's turned on as a running light.

Any help would be greatly appreciated. I am at a complete loss on this one... :mad: I've looked at wiring diagrams but the fool that had the truck before me did all kinds of weird things. BUT I never used to have this problem. It recently developed and I can't think of anything I would've done or changed to trigger it...
 

Co-Dog

Well-Known Member
Try replacing the flasher relay. You may be able to just swap from another vehicle to test it.
 

_

Well-Known Member
You need a proper factory wiring diagram to fully asses your issue. Without one, you may never find the problem. You will need to trace all related circuits, +12V and GND, to insure the integrity of each. Also, often times the turn stalk plays a greater roll than simply activating the turn signals. Meaning, run lights and/or brake lamps may pass through the turn stalk. If all wires are intact and proper per the factory diagram, the problem may be in the stalk. Again, get a proper wire diagram and test the circuitry in the stalk per the diagram. -OR- Just keep changing parts and replacing wires until you fix the problem.

"My guess" is you have a missing or compromised ground wire and the turn lamps are back feeding through the run lamp circuit.
 

ChromolyKid

Well-Known Member
Thanks for the advice, I'll try replacing the relay before I start tracing wires. Hopefully it's that simple. If not I'll go buy a Chilton's manual and try to locate the problem... Thanks again!
 

Mike_McCluskey

Well-Known Member
I am willing to bet it is the wiring harness in the column. My '94 Suburban is in the shop right now getting the harness replaced. It's a common problem with that body style. I've had 3 trucks and the Suburban all have variations of the same problem. Headlights work with column up not down, brakes lights work column up not down, and brake lights only, no running lights. All were diagnosed back to the harness in the column.
I use United Automotive in Orange. Excellent honest work, ex class 10/12 racer.
 

Shaggy

Well-Known Member
Something else to think about is if there is a aftermarket wiring harness for a trailer.
 

Co-Dog

Well-Known Member
I wouldn't just go buy a new relay. I didn't have time this morning to elaborate, so I tried to keep it simple. You may have more than one relay. Locate the clicking relay and verify it is the one by feel.

5. While the lights ARE on, if I try to signal, the rear light will light up for a split second like it's attempting to flash, but won't. Nothing from the front.

I have seen the problem you describe and it seems to be related to voltage drop in the system when the lights are turned on. The voltage drop is enough to keep an older relay from operating. I have seen the problem go away by just pulling the relay and putting it back. Doesn't take very much resistance from a dirty contact to cause voltage drop.

6. Not sure if it's anything significant to the problem, but the running light signal isn't nearly as bright as when it's turned on as a running light.

That might be important. Does that lamp have one filament or two?

What happens when you turn the hazards on? (With and without headlights on.)
Does the clicking comes from the same place as the turn signals?

Also need to know if the brake lights have any effect on the turn signal with and without headlights on. (That will help eliminate another possibility.)
 

ChromolyKid

Well-Known Member
Ok, went through an extensive hunt today with a family member that knows a lot about electricity. We've come to the conclusion that it IS either the turn signal switch or the headlight switch. I believe Mike McCluskey is right.
We found two relays on the flasher system, and they both work fine. Cleaned them both and tested them.
We pulled out the headlight switch and it was very dirty, so we cleaned it and tested it, not sure if it's working properly though because we haven't been able to get the turn signal switch out yet. Any tips on how to get it out of the column?
To answer your questions Co-Dog, the running light has two filaments. The hazards also DO work, but only with the headlights/running lights off. They are also on a seperate, slower flasher relay. And no the brake lights have no effect on the turn signals when the running lights are off.
I'm 75% sure it's the turn signal switch that's gone bad. But I will most likely replace the headlight switch while I'm at it, just to be safe. Looks like I'm going to pick-a-part tomorrow...
 

ChromolyKid

Well-Known Member
Here's a link for new parts for it if you don't find one. http://www.classicindustries.com/index.cfm
Thanks! That company is a lot cheaper than LMC. I didn't have any luck finding the switches at junkyards today so I'll probably order the parts tomorrow after I run one last test... After tearing through a few steering columns today, I'm not sure I have the tools and/or experience to replace the turn signal switch, so I'm considering having a shop do it instead. Suggestions?
 

Co-Dog

Well-Known Member
Headlight switches can be pretty tough to test without a schematic of the switch itself. My money is on the headlight switch at this point. Everything points to it and Chevy light switches are notorious for getting hot due to undersized wiring. The heat makes the contact resistance go up, and after a while it affects the wiring itself. Look closely at at the wire insulation near the connectors. The insulation will tend to loose its shape and sag or oval if it has been getting too hot.

Have you checked the voltage at the turn signal lamps. If you have a low voltage there, and the problem is the light switch, you will likely find that same voltage at the terminal that is causing the problem. The same goes for the turn signal switch, but it is doubtful that the problem exists there.
 

ChromolyKid

Well-Known Member
Wow... What a day. Went through and diagnosed more possibilities, bought a new headlight switch and flasher relay, put them in and there was still problems. So my dad pulls out one of the LED running lights, which we'd done a hundred times before, and takes a close look at the bulb...

It was in backwards :eek:

Turned it around and it all works fine.

You can all laugh at me now.

But WAIT! There's more... You all know these stories never end happy, right?

I went to start my truck and surprise, the key won't turn. Interesting, so I try to pull it out. Nope. Not happening. Stuck in between the "On" and "Accessory" (or whatever you call the first click) position. Can't believe it. Was working fine literally FIVE MINUTES before that. Last time we had tested the signals it worked great. Is there some kind of anti-theft device on these that locks the cylinder after messing with electrical?

Just went to Autozone, bought a new ignition cylinder, went through hell tearing apart the steering column to get the new cylinder in, and guess what? Still doesn't work. Man... I'm thinking about calling a mobile mechanic 'cause this is getting ridiculous. In the meantime, I'll be signaling great in my driveway.

This really sucks, I was going to take my truck to get it painted tomorrow... :(
 

Co-Dog

Well-Known Member
Your not the first guy that failed to mention that he had installed LED's. At least the wild goose chase was easy on my end this time. Sorry your having such a run of bad luck. I know how to change that.......get a Ford.:D Had to say it, forgive me.

Turn the steering wheel hard to one side, I mean hard like your trying to strip the splines off the shaft, while doing that see if the key will turn. Saw the fleet mechanic at work do that to one of the Chevy's when it wouldn't give up the key.
 

ChromolyKid

Well-Known Member
FIXED!!! :D
This is the stupidest thing ever: I have an Artcarr in my truck, so the stock column shifter was simply pulled out. BUT, the sleeve that surrounds the column is still there. It must have some sort of contact on it, that tells the computer what gear it's in when it rotates. So while messing around with the electrical yesterday, we must have rotated it into "gear" (or at least the computer thought so) and therefore locking the key...

Yes, I took apart the whole steering column, beyond the turn signal switch and ignition rod, to figure this out...

Haha thanks for the advice Co-Dog, but you know how it is. The brand you're raised with is the brand you stick with.

Thank you to everyone who helped! Hopefully I can return the favor someday. I'm slowly becoming a wizard of useless GM knowledge...
 

Shaggy

Well-Known Member
Glad you found it. Sometimes I have to walk away for an hour or a day then come back to it, otherwise I get sideways.:D
 
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