Reproduction Parts for 1916-1964 Chevrolet Passenger Cars & 1918-1987 Chevrolet & GMC Trucks
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I have been messing with my 29 headlight switch for a while. Everything seemed to work properly except the park light position. The park wire was grounded out and kept blowing the fuse. I was afraid to take the switch apart but in the end I did. It’s a very simple yet elegant little switch. But there doesn’t appear to be a thing wrong with it.
Since the park light wire was grounded out. Removed the wire from the switch and tested the switch and the wire separately. Figuring that this would tell me if the switch was the issue or the wire. (The wire is part of my new DIY harness…the switch is 96 years old) When tested separately neither one showed continuity to ground.
Instead of just putting the wire back on and testing again I decided to remove and rebuild the switch. It looked fine on the inside. (see attached) I cleaned it up a bit and put it back together. It seems to test fine on the bench. I am making some assumptions here but:
Off position - Tail/Brake/Dome/Horn all have continuity to power (in all positions)
On position - Headlights have continuity to power as well as the ones mentioned above
Park position - is the only position that park has continuity to power (Park lights get power, headlights do not everything else is on as above)
I checked before I removed the park wire from the switch to see if there was any contact or cross talk between the terminals. There didn't appear to be any. The only thing I can think of is that the screw on the park light wire was close enough to make contact with the plate inside the switch but that wouldn’t necessarily show a ground but it might short the fuse.
Anyone experience this type of issue with the switch or wiring before. I would love to sort this out.
I also rebuilt the harnesses inside the headlight buckets. That was a fun job.
According to the wiring diagram the head/park, instrument and tail lights should not have power with the switch in the off position. Do you have everything connected to the correct terminal on the switch? The park lights connect to terminal S, the head lights to terminal H and the tail lights to terminal R.
https://chevy.oldcarmanualproject.com/electrical/wiring/pdf/2930wiring.pdf
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1938 Master Business Coupe
1953 210 Sedan
Tiny, You are correct. I must have made a mistake testing or documenting. Im testing via continuity because the switch is out of the car. So I am testing continuity from the terminal where the power comes in form the ammeter (12 o’clock position between the S and H terminals) to each of the other trerminals
In the “off” position I have continuity brake/horn and dome only.
In the “on” position everything has continuity except the park light.
In the “park” position everything has continuity except the headlights.
I am positive these were connected to the correct terminals. I checked and double checked when I was wiring the car.
The switch seems to be fine. I am still puzzled that the park light was shorting out but when I disconnected the wire from the switch the wire is not shorted to ground and neither was the switch.
Maybe I am testing incorrectly. Electrical problems are my Achilles heal. So of course I have a weird one on my hands.
Update. After cleaning the switch and reassembling it I reinstalled and everything works as it should.
When I took the switch apart I noticed some chips missing off the back of the knob. I didn’t see any pieces in the switch but they must have been in there and were shorting the plate in certain positions.
It’s the only thing I can think of as I didn’t change any of the wiring. But I have park, hi/lo beams, tail and brake lights. And I haven't blown fuse yet today.
Though I did almost blow my own head gasket trying to put the gauge back in and reassemble the dash. But I am a happy man today.
Rich
Good job.
7046 old site posts
Save a life, adopt a senior shelter pet
There are many good people. If you can't find one, be one.
1938 Master Business Coupe
1953 210 Sedan
@tiny Thanks Tiny, I was really worried about taking that switch apart but after all the testing I did it was surely the culprit. So I could either do it my self or find someone to do it for me. I am impatient so I figured what’s the worst that can happen. If all else failed I could just install a bus bar under the dash with a few toggle switches on it to run the lights. Luckily it all worked out. It is a very simple switch considering all that it does.
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