A short, or something else?

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Saverio

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I have what I believe to be a weird issue, and need some help trouble shooting.

My instrument cluster lights work IF I twist the dimmer to just the right spot.
They do go on and off if it's not set just right. Could that be a short somewhere?

My LEFT turn signals work (both on the top fender and cluster), but the RIGHT side does not.
However, when I turn on the blinker I can hear it working, it's just that the fender indicator and cluster indicator lights don't come on. They were working yesterday!

Where would I begin to look for and repair the culprit?

This is on a '74 Plymouth Scamp / 318, w/ AC.
 
I should also note that when I pull the hazard lights, only the left side works as well.
 
The headlight switches do go bad, I would start there. Sometimes they just get dirty, removes the switch and check it over.
 
Most likely a bad headlight switch. The turn signal issue might be a bad ground or wire connection, trace and inspect wiring harness/connectors under hood to turn signals and in trunk.
 
The dimmer control in the headlight switch is called a rheostat. This is essentially a resistance wire with a sliding electrical contact. They do get "bad spots."

The turn signals might be a couple of different problems


Does your actual right side signal bulbs work in the front and rear?

Might be bad bulbs in the indicator lamps, or bad grounds.

For the cluster, these are twist in sockets, so bad bulb, bad or dirty or loose contact fingers in the bulb socket, or dirty contact areas on the PC board, or a loose connector pin at the PC board connector

The fender same deal, bad bulb, bad ground.
 
thanks everyone!

I didn't think to remove/inspect/clean the headlight switch. I will do that tonight.

For the bulb sockets at the pc board - I did remove, clean (deoxit worked great), and replace all of the bulbs - so it's very possible that I very stupidly knocked something loose. I hope I didn't break a pin.

Another thing I read was that the screws for the cluster can pierce the harness wires, so that'll be another thing I check.

67Dart27 - I think it was you who suggested (in another thread) to add a separate ground wire to dash frame for the pc board. A great suggestion and I plan to do this tonight.

I'm sure I'll find the problem, it will just bug the crap out of me until it's fixed!
 
Also, just twist the light switch knob vigorously from left to right several times. These get dirty, and this might scrape the corrosion off
 
67Dart273 said:
Also, just twist the light switch knob vigorously from left to right several times. These get dirty, and this might scrape the corrosion off
Click to expand...

Thank you 67Dart273 - this worked!

The blinker issue: I traced all the wires looking for damage and they were actually ok. Took the glove box out/off and found the flasher relay near the ashtray - twisted up and half plugged in. Pretty sure the flasher had been replaced (the "made in mexico" stamped on it gave it away).

Cleaned off the pins, mated and de-mated a couple of times and voila! All lights back to normal operating status.

I think my next project will be converting the amp bypass mod, as explained here: http://www.madelectrical.com/electricaltech/amp-gauges.shtml
 
Sometimes you can clean the rheostat dimmer with WD-40. Just spray it on and move it back & forth several times, it might work.
 
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