The Stovebolt Site Forums The Parking Lot '60-'66 Trucks Wiring turn signals on 64 GMC K1500

OK, so I got my new turn signals in, now it's time to wire them. The painters just cut the wires but there's a portion of the wiring running in within the hood. So I have the original light blue, dark blue, and violet wires.

I took the wiring diagram from the manual and "erased" everything I didn't need. Here's the pic:
1964_GMCwiring.png http://captaincheeto.com/pictures/64-gmc/turnsignals/1964_GMCwiring.png


I wired it up just as shown here. Here are my results:
1. I have no parking lights (but the rear lights do work in parking mode.

2. When I engage the left signal, BOTH signals blink bright (bottom bulb filaments).

3. When I engage the right signal, only the right one blinks, but dimmer (using the bottom filament).

In both cases, the turn signal indicator on the dash blinks.

I'm pretty stumped. I removed the light blue wire from the firewall, and got the exact same results. If I remove the dark blue wire, both blink for left, netiehr for right. The dash indicator still works for both. If I remove the violet wire (supposed to go to the light switch connector) then I get nothing.

Now the ONLY thing I didn't do per the diagram was have the violet wire connected at the left light and then to the right light. But they're connected together, more in a Y... i.e. the wire comes from the firewall to the middle of the hood, then does a Y to both lights.

OK wiring gurus, what's going on? It appears I have the original wiring, so I would expect it to all be intact.

I told some info, but then I realized it may not be true for a '64.

I'd bet you need to ground your turn signal housings/sockets.

I did some more thinking on this, and when dealing with electrical issues I find it easier to work on one thing at a time. So, let's figure out why the parking lights won't come on. Get your test light and see if you are getting power to the sockets. If you are, try rigging a ground wire on the sockets to see if the lights will light up. Most of the time wiring issues boil down to bad grounds on these ol' girls.

The first thing I thought about was bad grounding... but if they weren't grounded, then they shouldn't work at all instead of the wonky way they are working.

But I agree, I need to isolate things and see if I'm getting the voltages when I expect to get them.

Actually, just about any time stuff works wonky its a ground issue-voltage backfeeds thru switches & bulbs such & lights work really wierd.

Like 64fleetside said, when the ground is bad things can work wonky. Here's an example.... Last fall on my '71 the taillights and marker lights stopped working correctly. When I hit the brakes, everything lit up. Blinkers didn't work right on the back, turn one on and it would light both up solid, turn on the other and both would blink. The fix? Ran two ground straps from the bed to the frame and it fixed it perfectly and haven't had a problem since.

What I'm getting at is this, don't just assume a bad ground would mean it won't light up. It's simply not the case. Always check the grounds first. Just run a temp ground wire to the sockets to test the theory. What do you have to lose but a little bit of time?

Hm, good points. I didn't know a bad ground could cause weird results like this. But if someone had seen it, I'll believe it. I'll give it a shot. (am out of town at the moment, but this will be the next thing I check when I get home)

OK, here's the latest:
I took the voltages at the engine side of the firewall of the 3 connectors. There were no wires running, so I was getting a good ground.
voltages are for the Top/Left/Right connector
Parking light on - 0/0/0
Left signal on - 0/12/12
Right signal on - var/0/var

var = varying voltage... so, blinking.

Per the diagram it should be Top (right signal), Left (left signal), Right (parking)

I think I'm going to have to dig into the parking light switch and do some wire tracing to the signal switch now.