73 dash light rheostat - follow-up

[Gary S.]

A while ago, I posted a question about a friend's 73 that had no dash lights but good headlight operations. Several of you responded and I will give you the short version. A repro switch now lives in his dash and all works fine. The old rheostat test ok, looks ok, and even seems to operate ok for everything but the instrument lights. Regardless, he now has lights to drive at night.
Gary

[Dick W.]

Re: 73 dash light rheostat - follow-up

Over the years I have seen numerous rheostats on various vehicles look like new but would not work. Most though are burnt so that there is no question. The only sure way to test them would be with an ohmmeter

[Gary S.]

Re: 73 dash light rheostat - follow-up

Dick, I did test it with an ohm meter and it was good. Now, I don't know if there was a hidden problem or not. At this point, it doesn't matter anymore. He now has lights, he is happy and on the road.

Moral of the story, don't believe your eyes!
Gary

[Robert R.]

Re: 73 dash light rheostat - follow-up

Gary,
Was it just the dash lights or did the running lights also quit? Currently, my '73 has neither dash, marker, nor tail lights. It does operate head lights and will also operate the interior lights under the dash. Either way, I do plan on changing the switch.

[Gary S.]

Re: 73 dash light rheostat - follow-up

Good question. I THINK (careful - qualifying statement follows) that he had all external lights since he said he was at a diner and the interior lights went out. He drove it home so I am ASSUMING that all exterior lights were working. The old, malfunctioning switch would turn on the courtesy lights when the rheostat was rotated fully. Of course, that is a separate function.
Gary

[Todd H 26112]

Re: 73 dash light rheostat - follow-up

The external lighting all operates on a separate circuit within these switches - any failure in both the dash lights AND the external lights would largely be coincidental in my opinion.

I've got two disassembled - there are 2 things you can do to clean up intermittent or non-working adjustable dash lights.

1 is the rheostat 'wiper' can get corroded - you really can't see it unless you fully disassemble - these things can also get brittle so don't bend or pry - simply hold and brighten up the contact points w/ some emery paper or something. You can also 'slightly' retension that spring that applies pressure to teh wiper.

2 the coiled resistor wire gets brittle or breaks at it's base typically. WHile you can sometimes see wear or scoring on the rubbed surface - sometimes the breaks occur down below or just near the rivet. You 'can' simply pull them out and flip/reverse them - new surface exposed and try either soldering or otherwise attaching riveting etc to re-attach to the base - heat may not make soldering a good idea...?

To disassemble you obviously pry those tangs back but I'm sure you were aware of that. Just take a good look at how it goes back together. WHile in there you can clean out gunky old grease on teh pull switch portion of the switch assembly - I would try and keep grease of the contacts and just brighten them up - I would't let any cleaners or solvents get in teh vacuum switch itself - just leave it alone presuming it works.

Out of curiosity what kind of ohm reading were you getting at the far end?

I think it's actually an elegant switch design - you get marker lights, head lights (including up/down in teh case of Vette and other hideaway light cars of the era), dash rheostat and interior light on/off - all from a single intuitive knob. Not bad!