Headlight switch hell on a 71

[jonny0666]

Anyone have headlight switches go on them frequently?

I have a 71. Had the headlight switch. Had power to everything but dash lights. Got a new switch, plugged it in under the dash first to test it and lights worked. Went to install it in the dash and Know she’s a no work. Now I can’t get it to light the dash. Rest still work... headlights, markers, etc. No power on either side of the 5 amp fuse either. Any advice?

 

[JimCoronette]

Do you have continuity from the clip to the fuse on each end? Sometimes they get corroded.

 

[jonny0666]

Good point. I’ll check tomorrow. Thanks.

 

[JimCoronette]

Good point. I’ll check tomorrow. Thanks.

The fuseboxes get soaked from leaky wiper pivot seals and end up corroding the fuseholders.

The fuse is good but doesn't get power to it or loses contact under load.

I went through this with my 67. Not sure if the 71s and up have this problem

 

[QuickBpBp]

Also the cowls rot out letting water in also causing electrical issues...

 

[jonny0666]

just re-did the whole front end of the car, cowl, and engine bay, ripped the whole dash harness apart and replaced anything that was burnt or corroded. but i'll re-check them. Thank guys

 

[Nacho-RT74]

rheostat sulfated ( that greenish stuff ) or points to rheostat loosing contact.

Cluster light fuse with bad contact... I have seen the tan ( wire coming from switch ) or orange wire ( running to dash ) on back getting loose ( or broken ) from fuse holders

 

[YY1]

did you try bypassing the dimmer switch?

 

[jonny0666]

Yes. Light work.

 

[70chall440]

#1 reason switches in the dash do not work properly is a bad ground. Many older Mopars (and I suppose others) relied on the dash mounting setup to provide a ground and over time it is corroded and lost. Of course this is not the only reason, just one of them. Second reason is bad or corroded terminals/connections.

 

[Nacho-RT74]

light switch doesn't need a ground to work, except for the dome light.

You could get a bad ground on cluster able to not turn on the dash lights but if so, you could burn the gauges too if VL is not grounded, and you have more lights around to light on with dimmer knob, like radio face, ahstray light, shifter. And all these get different grounds not related to cluster itself

 

[jonny0666]

It’s a brand new switch and I had it temporarily grounded with a test lead. Thought of that.

I’m now wondering if when I pulled the knob out to reinstall the switch, maybe I damaged something on the inside? Basically what I’m down to

 

[Nacho-RT74]

The rheostat wheel ( ceramic wheel ) gets a track and a point with the spring ( rheostat itself ) in the middle of the circuit. Have you checked the track and point and making contact with the spring assembly? Replacement parts are latelly POS.

And also wondering. Have you spining the headlight switch knob to try on several positions of the dimmer? This could sound basic but some ppl may not know the dimmer works rotating the headlight knob!

 

[Nacho-RT74]

This is a X car headlight switch. Doesn't matter, but all work the same, just can look a bit different

The yellowish strip takes to the central tracks between switch assembly and ceramic wheel. That should be the ouput from switch to feed rheostat

The redish strip takes to the point which will take the power after the rheostat ( spring ) and the rheostat position againts this point will vary the voltage going to dash lights.

This point must be making good contact with rheostat. It also gets a position where doesn't make contact with rheostat to turn off dash lights.

Central tracks must be also making good contact between them. On this pic there is a gap visible. It shouldn't exist any gap. Usually once the knob is in place the wheel keeps centered and saves all the gaps. Here it looks some twisted.

Somewhere around the wheel, there is also a tab which is simply pushed by a molded lever on ceramic, just to send ground to dome light. But that's a diff deal. ( I think is visible on a darker area on bottom part of the pic at wheel )

NOTE: I used this pic because is the only one I could find to show the dimmer assembly function. I think on your switch you won't find the yellowish stripe to feed the central track, because as far I recall on our 3rd gen switch this runs internally from parking lights circuitry ( mostly sure the is same than this pic but here is being taken externally )

 

[jonny0666]

well, i have new ideas to try and experiment with. I'll try all of these ideas and update. Thanks all.

 

[jonny0666]

So to update all:

it was a fried fuse connector on the back of the fuse block. The “cigar” fuse that feeds the switch. Apparently the wire fried and had a bad connection, but was showing power on both sides of the fuse. It just wasn’t going anywhere passed that. So now that I feel like an idiot, I wanted to thank you all. On to the next disaster project on this car.

 

[Nacho-RT74]

I thought on that on reply #7 because even I never have got a fried wire or terminal on back of fusebox, I have found the wire loosen on them because the fuse clip part what wrapps the wire can get broken easily.

 

[jonny0666]

I never noticed it because it was right off the connector. I happened to look last night and realized the insulation was bubbled and burnt a little. as soon as i touched it i saw that half the wire was fried. so cut it off, reattached the wire to the terminal, and a little heat-shrink to clean it up... worked like a charm.

 

[Nacho-RT74]

Apparently the wire fried and had a bad connection, but was showing power on both sides of the fuse.

so it was the batt one what feeds the switch itself and not the one feeding just the cluster lights. But you told were having sidemarkers, thats weird!... well, thankfully you found it!

 

[jonny0666]

yeah... well there are 2 power feeds to the switch... the 12v power that feeds the headlights and then the B2 power that comes from the "cigar lighter" circuit feeds the dash lights.