Instrument Cluster fuse blows

[blk81]

If I pull out the light switch and turn the knob to the left to brighten the IC backlights, the fuse blows. Bad light switch? It appears to be original. FYI, I installed the tachometer conversion kit with all the new parts included and all new bulbs. With the cluster removed, I checked the switch and the fuse blew even without the cluster plugged in.I thought maybe something was touching bare metal. All wiring looks good. Everything has been working fine up until last week. Blinkers and dome/courtesy lights all work. Headlights and parking lights work. I did search the forum and did not find an answer for this particular problem. Thanks for any help.

 

[Big Chip]

I have a vague recollection of some problem with my tail lights on my 86 and I would know they were out if the instrument cluster lights were out. Could have been a different car or truck though, I'm old.

 

[WP29P4A]

Did it work properly before "tachometer conversion kit with all the new parts included and all new bulbs."?

 

[Bextreme04]

can you clarify "turn knob to left". Does it blow when the lights are on at all, or does it blow when you turn it past the detent? All the way bright past the detent turns the dome light on, and if it is blowing at that point, I would suspect a short in the wire or a bad headlight switch

 

[blk81]

can you clarify "turn knob to left". Does it blow when the lights are on at all, or does it blow when you turn it past the detent? All the way bright past the detent turns the dome light on, and if it is blowing at that point, I would suspect a short in the wire or a bad headlight switch

It blows the fuse as you turn the knob to the left. Starting on dim and getting brighter. I can turn all the way left and turn on the dome and courtesy light. They are working.

 

[blk81]

Did it work properly before "tachometer conversion kit with all the new parts included and all new bulbs."?

Yes, before and after. For several weeks after I completed the interior the dash lights worked. Just started this. I suspect there's a problem inside the headlight switch.

 

[WP29P4A]

I agree on the headlight switch being suspect.

 

[Bextreme04]

Yes, with that description it sounds like the headlight switch is the most likely suspect. It could also be a loose/bad connection or some corrosion in a connector somewhere. Basically a bad connection will have a higher electrical resistance and therefore will draw more current, which will blow the fuse. Its most likely that bad connection is internal to the headlight switch... its actually fairly common

 

[blk81]

Replaced the headlight switch. Identical connections and function. Fuse blew again. Put a new fuse in and turned the light knob clockwise (away from the direction that the dome light would come on). Fuse did not blow, however, the light switch started smoking and got HOT. Unplugged it and disconnected negative battery cable since this was on lunch break today and came back to work. What now?