I have a 1999 C280 and while on vacation, the car was parked in a garage for 1
week (July 2008). When we returned, the left rear standing lamp was on and it
was the one that is the larger
2 filament bulb. The lamp was on the high intensity setting. We were able to
start the car with no problem. And when we started the car, the light went
off. But now when
the car is parked and the key removed, the lamp wants to stay on. We have removed
the bulb. There is 12 volts at the connector going to the lamp housing assy.
Can someone give me
some troubleshooting tips? What module might be involved? Thanks in advance
for your help.
Gary
A couple of stupid questions: In which position was your main lights switch, the knob vertically and not pulled?
If your front parking lights are fine and were not on while the rear one was, then it should not be the partial parking lights (left or right that come on when the main switch is turned to the left from the vertical position).
A single rear lamp comes on when the rear fog lamp is on but that should only come when the fronts are on first. And the fog should be on a different place at the lamp assembly from the parking lamp.
Is it actually your brake lamp bulb that has two filaments, one for the parking light and one for the brakes?
Would make "diagnostics" easier if you can tell the exact bulb/light that was on.
Edited: does your rear lamp look like the one in the attached figure?
Last edited by Diesel Benz : 07-23-2008 at 09:48 AM.
The headlight switch was in the "off" position when this problem occurred (knob veritcal).
From the diagram you provided, the problem is only on the drivers side. Bulb 5 (2 1/4 bulb) stays on with the keys out of the ignition, lamp switch vertical and all other bulbs are off. On bulb 5, there are 2 filaments - I check both the driver and passenger sides and both bulbs are the same. I even switched bulbs and got the same answer.
Here is the scenario for left and right standing lamps.
Left standing lamp position of switch and keys out of ignition - driver side lamps 4 and 5 are on.
Right standing lamp position of switch and keys out of ignition - passenger lamps 4 and 5 and driver lamp 5 are all on.
I checked trhe contact to the connector going to driver side lamp 5 and there is 12 volts. So it does not appear to be the tail lamp assembly but rather something that is powering on the 12 volts when the keys are out of the ignition. Again when the car is turned on, driver lamp 5 goes out.
We do not use the standing lamp feature, but would like to resolve this problem since we plan on selling the car soon - everything else is in excellant condition.
If I follow your description, then the rear fog lamp is on. You don't mention if your light switch is pulled and remains pulled even if I assume it should not? Since you don't mention the front fogs coming on, I would check the main lights switch if it is providing the fog lamp voltage even at idle position. Of course if you see power at that bulb, you could try to follow backwards the wire and find the source.
The switch was not pulled. I will try to pull it and see if it will reset when I push it back in. The whole thing just seems odd to me that the light came on at some point while we were on vacation (not long enough to drain the battery). No one was around the car - it was parked in the garage and no one had entered the car prior to the light being on.
Usually switch failures I have seen would be during the activation period versus an idle period. But who knows these days with all the various types of technologies in switches.
I have thought about following the wires back from the lamp but know that will take some disassembly work to see where they go.
So last night I pulled out on the switch for the fog lamps and pushed it back in. Did this several times. Reinstalled the bulb and now the light is OFF. HHmmmmm. So maybe there was something in the fog lamp switch that shorted out - piece of debris?? Now that I activated the switch, maybe it loosened up this piece??
We will monitor the light to see if it stays off. If this is the case, then it is a pretty strange occurance. I'd really love to know that this resolves this but somehow won't feel safe until its been at least a week or two.
The concern is will the lamp come on at some obscure time and drain the battery!!
Thanks for your help and I hope this resolves the problem.
So last night I pulled out on the switch for the fog lamps and pushed it back in. Did this several times. Reinstalled the bulb and now the light is OFF. HHmmmmm. So maybe there was something in the fog lamp switch that shorted out - piece of debris?? Now that I activated the switch, maybe it loosened up this piece??
We will monitor the light to see if it stays off. If this is the case, then it is a pretty strange occurance. I'd really love to know that this resolves this but somehow won't feel safe until its been at least a week or two.
The concern is will the lamp come on at some obscure time and drain the battery!!
Thanks for your help and I hope this resolves the problem.
Gary
I believe it could well be some debris at the light switch, I guess I already mentioned that these fail, on older cars they pass the full current for the bulbs. The dirt may have forced the rear fog light contact on.
Hopefully the issue does not come back, perhaps you should consider a new switch if it after all comes back.
It should be unlikely that the light comes on when the car is stationary (even if it perhaps already did once) and if it comes on, a single bulb would not drain the battery over night (21W bulb would drain 1.75 amps, 21 Ah within 12 hours, not too much for a good battery but a couple of days would run a good battery flat).
Last edited by Diesel Benz : 07-29-2008 at 10:36 AM.
1999 C280 Standing Lamp Stays On 
Linear Mode
