2001 U320. Above the headlight switch was small black spot and little smoke. Turned off ignition and headlights. Removed dash cowling. No evidence behind the dash. Talked to Mr Risch at MOT, sent photos.
He suggested it was caused by trying to burn the dash, probably try that first. He had me disconnect the two wires (black, white) and turn headlight switch on and ignition key. No heat felt or smoke seen. Seems solved.
However my friend Roger Engdahl had suggested before I had taken the cowling off that the dimmer to dash lights might be a suspect. So after I tried the unplugged dash electricity two wires, I turned the dimmer and saw no smoke or heat but could hear what sounded like crackle of electricity contacts in what I call the dimmer rheostat. Maybe normal sound?
I think Risch found the cause. I had felt the dash hot on the left (driver side) of the light switch which it turns out would be where the round thing with the black and white wires connect.
Think this is a very rare event but maybe it would be good to have in your quiver of very seldom needed arrows of knowledge.
Dash lights at full brightness should take the reostat and the heat out of the equation, use some contact cleaner on all connections. Don't ask me how I learned this, so far about $84 and 20+ hours
Mike,
I would just replace the switch. You know it has failed at least once. Don't roll the dice that it will happen again and cause real damage.
Is that some of that paint that glows at night?
something like this
(https://photos.smugmug.com/Foretravel/Forums-post-1/i-dK7WC3b/0/2677274d/M/20180120_135146-M.jpg)
Burn looked similar but as for same, I not sure...dash on my coach not so colorful I thinks.
Thanks for reply
I would normally agree with replacement, except the quality of the replacements can be beyond sad, switch #3 is supposed to be genuine ac delco for my coach, and has not arrived yet, maybe tomorrow. Special order $44. Hindsight I would have jumpered around the rheostat that was hit and miss on my coach.
Mike, you might just take the rheostat out of the equation and wire around it. The dash is on full brightness all the time then. My backup cameras don't like something when the dimmer is engaged and behave better at full brighness.
It looks like wire #73 provides power to the rheostat and #73A sends reduced voltage to dash and switch lights. Disconnect the plug and have no dash lights or jumper from 73 to 73 A.
Or just cut the red and white wires at the back of the rheostat and connect them by the plug.