Strange Turn Signal Problem

[NoForAnAnswer]

Ok folks. Here's a noodle scratcher for ya! I was driving my truck home from work today and when I almost get there, the left turn signal starts going wonky. When I try to turn it on it doesn't work and the battery gauge is going ape. After I pull over and look a bit closer it appears that the battery gauge it "turning" to the left as my signal should. Also, my sunpro tach is dipping the needle a bit too with the signal on. All the while no flashing on my exterior lights. When I got it home, I disconnected the fuse for the battery gauge abd tried the signal again. It worked normally this time. So I hook up the fuse again and it dips to the left but not as far. Went away to talk to my dad about my problem, came back to try it all again and this time the gauge it "blinking" all the way to the left again and the lights aren't working. So, I turn the headlights on, turn on the left turn signal and every exterior light is blinking. Headlights, marker lights, tail lights both turn signals all of them. Decided to come back to it later as I had to leave for my second job. I come back after I get home a second time and check it all out again. Now the left turn signal works and blinks. The battery gauge is "blinking" left as well but not all the way. All the other lights work just fine. just the left side turn signals are giving me problems.

I think it may be a bad ground because I have a CB installed and wired to my aux battery (charged via isolator) and the last time I tried the turn signals when they would blink I would get static on the CB.

I plan on tackling this on saturday. Any ideas where to start looking?

Oh yeah. '71 K10 factory harness not butchered up. We're the second owners and we've had it since '83.
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[NoForAnAnswer]

Well, I took out the fuses for the battery gauge and changed the flasher and all is well with the turn signals. My CB is still bleeding into my stereo. I think I'll try to ground it directly to the aux battery and not to the common dash ground, see if that helps.
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[NoForAnAnswer]

Well, the problem came back. Driving home from work one night my left turn signal starts flashing all my exterior lights. Right signal is just fine. I get home, look under the dash and find the purple wire on both sides of the plug is starting to melt the insulation and the light blue wires also. I tried 2 other flashers and the problem pursists. Last week I bought a new turn signal switch but haven't had time to put it in yet.

Also. I was trying to show a friend of mine my problem and the left turn signal worked just fine like there was no problem at all. Nothing had been changed and I hadn't done anything to fix it. I will not drive my truck until this problem is resolved.

[NoForAnAnswer]

Since no one is offering any help. I'll just post my progress anyway.

I crawled under the truck and re-attached the licence plate light wire as the bare wire was hanging down. Opened up the left rear turn signal housing and cleaned up the grounds. Check the left turn signal again, it works but it's also making the battery gauge move when the light blinks. So, I check under the dash by the fuse box and traced the melted wires. The purple one is only melted by the terminations by the column plug. Light blue one is doubled up on a single contact. One of the 2 is melted all the way to the firewall. Now if I understand the wiring diagrams correctly, the light blue wire provides the signal power from the switch. Tomorrow, I'll be tracing the melted light blue wire fron the firewall to the light. Then I'll check the wire from the plug to the firewall.

If anyone has any advice please chime in

[VetteVet]

The purple wire is the signal light power wire from the flasher.
The light blue wire is the power wire for the left front turn signal and the piggyback wire is the power wire for the left turn signal light in the dash cluster.

[NoForAnAnswer]

So I crawled under the hood today and traced the light blue wire all the way to the turn signal plug. The wire under the hood looks just fine. No signs of damage or heat. I tested the plug for voltage, the running lights showed a steady 4 volts and the turn signal showed a fluctuation between 1-6 volts. After that I pulled the plug off the firewall to have a look behind the fuse box. And the light blue wire is burnt from the firewall side of the column plug to the fuse box and nowhere else it looks like.

And tips as to how to handle this or what may have happened?

[72gmcshorty]

Pull a Mike Holmes...rewire the entire truck... open it up, cut and splice. Unfortunately, the wires get old and brittle. The insulation starts to fall off, connections start to rust, grounds come off, etc and then bad stuff like this starts happening. Only way to properly fix (100%) is to rewire with new harness. You can fix the broken section but every other wire is still as old as the piece replaced.

Easy solution is to cut broken section out, splice in new piece (could butt splice but solder would be ideal) and heat shrink.

[VetteVet]

Good advice Shorty if he can afford it.
Most of the problems are directly caused by bad grounds. I don't know how many members have posted with this same complaint. and nearly all of them were traced to bad grounds.

There are two ways to blow a fuse and both of them are caused by the same thing. Having too much amperage going through it. A direct short to ground is the most common one. The other is too many loads trying to go through the fuse circuit at once trying to find a ground.
If the rest of the wiring in the harness looks pretty good then just replace the burnt section of the light blue wire and clean up and ground all the lights and run new ground wires. Before you apply power to the lighting circuit you should do a continuity check between the fuses and a good ground looking for a zero ohms reading which indicates a short to ground.
If you get more that zero it means that the wiring is going through the loads and not directly to ground.

If you still have problems then post back and we will help you trace the circuits and find the problem. VV

[NoForAnAnswer]

I got a chance to splice in a new wire for the burned up light blue. Ended up cutting the wire on both sides of the switch plug and splicing in an insulated spade in its place. The turn signals work just fine now. One thing is that when I turn either side on the battery gauge moves a little bit and I can't remember if it did that before or not. Just to recap, I checked the entire length of the wire and found the only problem being in this section of wire. All the plugs were not melted or showed any signs of heat. All other sections of wire looked to be in working order and not damaged or melted.

I plan on re - wiring the truck eventually but I'm a bit too poor at this time.

Thanks for all the help and I will keep this thread alive if there's any other problems that should arise.

[NoForAnAnswer]

Originally Posted by VetteVet

If the rest of the wiring in the harness looks pretty good then just replace the burnt section of the light blue wire and clean up and ground all the lights and run new ground wires. Before you apply power to the lighting circuit you should do a continuity check between the fuses and a good ground looking for a zero ohms reading which indicates a short to ground.
If you get more that zero it means that the wiring is going through the loads and not directly to ground.

If you still have problems then post back and we will help you trace the circuits and find the problem. VV

When I get a chance this is what I'll be sure to do. Running new grounds is a great idea. I just needed to get the truck back on the road so I could drive to work again as my 4 cylinder commuter truck crapped out on me.

[VetteVet]

Thanks for the feedback and it's quite normal for the battery gauge to deflect a little bit to the discharge side when the turn signal activates. The same thing will happen when the headlights are turned on or when the heater fan is engaged. Just as long as the gauge returns to the charging side, showing that the alternator has kicked in.

[In The Ten Ring]

Oh goodness! I wonder how soon I'll start running into problems like this when I try to get my truck back on the road!

I am almost completely ignorant when it comes to anything electric.