1996 C280 Courtesy Lights, Sunroof, Radio Key
 

Hello C280 Enthusiasts
My 1998 C280 has electrical issues with the overhead console as the Front Courtesy Lights, Sunroof, and Radio Key do not function. The rear overhead light works when the door is opened but not with the console switch. And the Infrared Key function works.
Any help would be greatly appreciated. Thank you.
Richard

(Please note that vehicle year is 1998)

The C280 had a recent plugged drain problem under the hood which spilled water into the passenger floor. This has been corrected. During the course of the leak there was also a problem with the fan running slowly when the key was shut off. This persisted even when the climate control module was removed and disconnected. The battery was drained then was disconnected then recharged. It was necessary to re synchronize each window following the battery disconnect.
So any ideas where to turn next or what to test to get the dome lights sun roof and key radio wave function restored? I did visually inspect all the fuses in the trunk and under the hood. Thanks

Does anyone have a suggestion for how to approach this electrical problem? Thanks.

considering you got water in the car, depending on how much water, I would also check the passenger side door sill/floor area. pull up the door sill plastic trim and pull back the carpet, theres wiring and connectors that's probably corroded.

Thanks Chassis221!! The water persisted over several months so I will sure check out the passenger side under the carpet and will report back.

Well I peeled off the plastic on the passenger door jambs. It's clean and dry in the wire trays. There is some minor puddling remaining on the floor pan however. The wires go forward under the dash and rearward under the seat. I need some tips on back seat removal and front side panel removal. Is there a link for a wiring diagram to isolate my break in circuitry. There sure are lots of circuits in the car. Yikes. Thanks ever so much.

C280 electrical -- continued
 

The C280 problem continues. It also now manifests as a continuous fan motor running. Even if the vehicle is off w key removed. Even when the climate control module is unplugged and removed. It makes me think that the defect is under the dash. Any insight would be most appreciated.

I would remove the passenger side under dash panel. 2 or 3 screws, remove the cover for the blower motor, then I would remove the blower and most likely youll see rust and also the blower regulator which sits beside the blower is probably the reason why the blower motor is running.

fan regulator
 

I replaced the fan regulator with a new one but the same condition exists.

The fan still runs if the key is removed. The fan runs regardless of the setting on the climate control. It still runs when the climate control module is removed and unplugged.

With the climate control module put back in, pushing the REST (Residual Engine Heat Utilization) button, the fan blower speed changes significantly. Repeating this on and off mirrors that result. There is a noticeable click in a relay under the dash directly under the glove box, when the REST button is pushed. Unplugging this relay has no effect. This is to say that pushing the REST btton with the relay unplugged still results in motor speed change.

It seems to me that the sensor which deactivates the REST function at temperature decrease has failed.

Anyone have a comment on if this makes sense and where that sensor might be located.

The failure of the fan to shut off occurred at the same time that the windshield drains plugged and the back passenger seat filled with water and the the drains were cleaned out.

For now the fan needs to be unplugged when vehicle is off lest the battery drain completely.

I could put an auxiliary switch on the fan but this is not preferred solution.

Any ideas, and thank you

:mad: