Only one headlight, is there a headlight relay? - PeachParts Mercedes-Benz Forum

ROLLGUY · #1 12-17-2010, 08:28 PM

On my 1982 300CD, only the left headlight works. The right bulb is good, fuse good, and wiring connections seem good. Both high beams work. Is there a headlight relay? If so, where is it located?
I am not sure if this is related, but there is also no power to the dome light. Again, the fuse is good and the door switch checks out (ground is good). If I apply 12V to the red wire on the dome light, it works as it should. Anyone have any ideas?

SD300 · #2 12-17-2010, 08:53 PM

these fuse can be real Bit*h, it can look good but no juice pass thru, if u know which one then just replace with a brand new one.
few wks ago my heater fan suddenly died i just put a new 1 in and it worked.

ROLLGUY · #3 12-17-2010, 09:05 PM

Quote:

Originally Posted by SD300

these fuse can be real Bit*h, it can look good but no juice pass thru, if u know which one then just replace with a brand new one.
few wks ago my heater fan suddenly died i just put a new 1 in and it worked.

I tested each fuse with a meter on both sides of the fuse. They all have 12V on both sides.

Yak · #4 12-17-2010, 09:11 PM

There are separate fuses for each filament: L lo = 13, R lo = 11, L hi (and dash indicator) = 9, R hi = 7. The fogs are also off 11. Do your fogs work? (Maybe obvious, but pull the switch towards you when the lows are on. If not, probably a bad fuse or connection at 11 causing the problem.

Does your rear dome light work? (switch on console) That gets power from the same circuit. If so, the fuse is obviously good. I had to clean the switch in the front dome light in my '83 CD, so it may just be dirt/grime. It was intermittent until I disassembled and cleaned.

ROLLGUY · #5 12-17-2010, 09:16 PM

Quote:

Originally Posted by Yak

There are separate fuses for each filament: L lo = 13, R lo = 11, L hi (and dash indicator) = 9, R hi = 7. The fogs are also off 11. Do your fogs work? (Maybe obvious, but pull the switch towards you when the lows are on. If not, probably a bad fuse or connection at 11 causing the problem.

Does your rear dome light work? (switch on console) That gets power from the same circuit. If so, the fuse is obviously good. I had to clean the switch in the front dome light in my '83 CD, so it may just be dirt/grime. It was intermittent until I disassembled and cleaned.

Both high beams work, so I assume those 2 fuses are good (even though all fuses were checked). If I remember correctly, the fogs do not work. I will check the rear dome light, but as I remember, it does work. I will also check the connection on fuse 11 (fogs do not work).

layback40 · #6 12-18-2010, 05:10 AM

Probably worth checking every connection between the switch/relay & the lights. One bad connection will kill lights.

willjohn123 · #7 12-19-2010, 05:09 PM

I had a corroded connection on the plug that is on the backside of the headlight/foglight bracket, causing the bulb not to work when everything else was OK. Mine was so bad that I had to bypass that plug & harness and connect the wires straight to the headlight plug.