new electrical issue- dash lights out.

[bljones]

a few days ago, i turn on the lights, and the switch starts to smoke, and the dash lights go out. headlights still work but no dash lights. i clean all the grounds under the dash, look for bad wiring- everything looks okay, replace the fuse, clean the connections on the back of the switch, reinstall, and everything works fine for a week or so. then, two days ago the same thing happens again. i replace the switch with a "known good" used switch from my parts stash, and clean up the grounds again. then tonight, the same result- smoke, and the dash lights go out.

Anybody have any thoughts? bad headlight relay?
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OG JHC
Author of Original Rant #1
"It stingd itself to dead... now that is control on you"

2%

[msinabottle]

What kind of headlights are you running? If you put in something heavy duty, like REAL halogens, you'd get that.

Best!

[grahamaaron]

Hi there,
Where was the smoke coming from? If the smoke was coming from the switch itself it’s normally a replacement job. Check the switch contacts by removing the switch from circuit and switching it into the ‘ON position and measuring the resistance. The resistance of a closed switch should be well (well and truly) under 0.5 ohm (perhaps as low as 0.01 ohm) When measuring the resistance, make sure the spade terminals on the back of the switch are clean and press down hard with your multimeter/ohmmeter probes. Closed switches will start dissipating heat (if it is switching a significant current load) when their on-resistance is too high. If the switch is not causing the smoke then you will need to determine the true origin. Good luck

[walrus]

If you happen to melt the switch while it is in the on positioin don't pull all the fuses to turn them off, just unplug the switch.
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1987 Syncro west. conversion
1991 Jetta gli

[psych-illogical]

I had a similar issue with my 83 Westy a couple of weeks ago. Unfortunately I could not determine the cause. I was driving home at night and smoke started rolling out from under the dash. It cleared quickly so I kept driving but my dash lights were out. A quick check showed that everything else was working properly. When I pulled the instrument cluster out, virtually every wire associated with the dash lights had the insulation melted completely off of it. The rheostat in the headlight switch for dimming the dashlights was melted. The only thing I can think of is that there might have been a bare spot on a wire that shorted to ground and started drawing a bunch of current and the switch sort of became the fuse and melted down or, the switch itself shorted out. There was so much damage to the wires that it was impossible to tell if there had been a bare spot. I replaced the switch and all the melted wires and it seems to be working fine now. If you had smoke, chances are you did start to have some insulation burn off. Check the wires very carefully. In mine, the dash light wires are the grey with blue stripe. Just for fun, I threw an in-line fuse in just downstream of the switch.
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83 1/2 Westy waterboxer
'57 Beetle-sold
Coupla '81 BMW motorcycles (R80G/S; R100RS)
'96 BMW R1100GS