Both signal lites flashing in the front, tail lites are fine
 

So, if I turn on the the right signal both lites and side markers flash. The same occurs if I turn on the left..tail lites and break lites and 4 ways work properly.

I double checked all my grounds, signal lite buckets,cab/frame/engine/dash cluster grounds are all good and clean. I replaced the bulbs and cleaned the connections..I was thinking about replacing the column anyways (wanted tilt). That didn’t fix it..it is a step side and the rear tail lite assemblies were replaced years ago..if it was the flasher gone bad wouldn’t the tails be flashing on both sides as well?

Does anyone have any ideas where to look next?
The truck is a 1971 GMC shorty stepside

Re: Both signal lites flashing in the front, tail lites are fine
 

I can't tell what the problem is from what you describe. Can you describe in more detail exactly what it is doing right, and what it is doing wrong?

Re: Both signal lites flashing in the front, tail lites are fine
 

Sounds like your parking and turn light up front are swapped. parking should be dimmer than turn (I think). I had the same problem on my 71 when I bought it.

Re: Both signal lites flashing in the front, tail lites are fine
 

I would suspect the connections in the turn signal switch or possibly the two dash turn indicator lights are shorted together. I don't think there is anything wrong with the flasher.

Here's how to troubleshoot.
to eliminate the turn signal switch, disconnect the half moon connector under the dash and locate the half that goes to the front lights.

find the purple wire in the center of the connector, this is the power wire for all the turn lights.
With the key on this wire has 12 volts power on it from the flasher to light all the turning bulbs.
Jump this wire to the dark blue and the dark green wire in the same connector, these are the right turn light wires, and see if the left turns also flash.

If only the right turns work then there must be a short in the turn signal switch.
If the problem persists then pull the cluster plug connection to isolate the turn indicator light wires in the dash and try the test again. Post back with the results.

Re: Both signal lites flashing in the front, tail lites are fine
 

Thank you for the response, all 3 of you. I just remembered something the first time I seen the signal lites both flashing was after I reinstalled the the gauge cluster. I had removed it to install a new fuel gauge. (The new gauge works perfectly) to install the new gauge you have to partially disassemble the back of the cluster by removing bulbs an pealing back the printed circuit board...is it possible I put the bulbs back in the wrong position or possibly the bulbs are in backwards? Or I damaged the circuit board?

What do you think Vette? I’m willing to try what you guys have said to look for.

Re: Both signal lites flashing in the front, tail lites are fine
 

In my first sentence I suggested that the turn indicator lights might be shorted together and you should pull the cluster plug to see if your problem goes away.

here's a diagram of the cluster wiring.




Attachment 1798510

Terminals nine and ten are the wiring paths for the turn indicators.
The two wires should be light blue and dark blue at the cluster plug
Pulling the cluster plug will eliminate a short in the cluster, however there are other places they might be shorted.

Re: Both signal lites flashing in the front, tail lites are fine
 

Sub'd for future reference :metal:

Re: Both signal lites flashing in the front, tail lites are fine
 

Just to let ya’ll know what I found is when I carelessly pushed in the clip on the back of the gauge cluster I twisted some of the copper tabs on the circuit board, I straightened them and reinserted the clip a little more carefully and everything works properly now..

Thanks VetteVet

Re: Both signal lites flashing in the front, tail lites are fine
 

Excellent. Always nice to see what can cause a problem, so we can maybe avoid doing the same thing.