no Dash lights - PeachParts Mercedes-Benz Forum

minidavid · #1 12-01-2005, 10:35 PM

All dash lights have now shut off. Instrument cluster included. I have checked all fuses and they work. All other electrical systems working. 1988 300E.
Can this be a faulty headlamp switch or relay? Any ideas?

sokoloff · #2 12-01-2005, 11:32 PM

Bad rheostat on the dimmer switch? Try jiggling the dimmer switch and see if they come back on. If you just reset your trip meter, that could have turned them off too.

Len

86560SEL · #3 12-02-2005, 12:08 AM

Year and model of car ?

minidavid · #4 12-02-2005, 08:56 AM

The car is a 1988 300E. When I stopped for fuel, all lights were on and working. I shut off the light switch and ignition, fueled and then reset the trip button as I would normally. I then restarted the car and put on the light switch. All lights function, but the instrument cluster, radio, shifter, vent lights.
You mentioned the dimmer switch. Where is the dimmer switch on this car?

page62 · #5 12-02-2005, 09:10 AM

Quote:

Originally Posted by sokoloff

If you just reset your trip meter, that could have turned them off too.

I gotta ask...how does resetting the trip meter cause the dash lights to go off?

donbryce · #6 12-02-2005, 09:51 AM

(Guessing that my 85 380SE is similar) The trip reset is a rod/plunger type of setup that sits above the rheostat switch. The same rod engages the switch and allows it to be turned clockwise/counterclockwise to vary the resistance in the circuit feeding the light bulbs. The thing is very touchy and can cut off the power easily, for reasons like the mechanical linkage wearing out, or corrosion in the rheostat (potentiometer) wire/contact.
I've had my instrument cluster lights go out when the bulb contacts inexplicably fail to pass enough current to the 2 bulbs. I spent hours pulling the cluster and the rheostat switch, trying to find the failure. In the end, I wiggled the bulb holders in their sockets and that did the trick.
In your case, since the entire light circuit is out, wiggle the rheostat/trip reset button and I think you'll find the problem there. A permanent solution is to pull the cluster and remove the rheostat switch entirely, then jump-wire the 2 contact pins together, effectively sending all power to the lights (which certainly will not 'blind' you with their intensity!)

#7 12-02-2005, 09:52 AM

Quote:

Originally Posted by minidavid

The car is a 1988 300E. When I stopped for fuel, all lights were on and working. I shut off the light switch and ignition, fueled and then reset the trip button as I would normally. I then restarted the car and put on the light switch. All lights function, but the instrument cluster, radio, shifter, vent lights.
You mentioned the dimmer switch. Where is the dimmer switch on this car?

Try rotating the button that you use to reset the trip odometer to the right, that is the dimmer on many models, I'm not sure about yours.