Hello Everyone,

I am new to the forums, and just got myself a 1994 E320 4 door the other day, and am really enjoying it. For most part, the car is in great shape and it is a comfortable car. That being said, there are a bunch of small problems which I have spent the last few days scouring this forum looking for anything that might suggest a common thread. I can't seem to find anything in particular and thought I would ask the forum if they knew what might be causing the problems I see.

1 rear window defroster doesn't work. The yellow light on the panel switch turns on, and I have replaced the #10 fuse with a new blue 25a fuse, but nothing happens.

2 rear-view mirrors won't move via the centre console stick. The fuse seems to be fine but am not sure if there is anything else that might control this part.

3 interior lights won't go on when I open the drivers door. The light go on when all other doors are open, so I think it is a sensor problem.

4 rear seat head rests won't lower when the console button is pressed.

5 engine idles a little rough between 500 to 1000 rpms. Doesn't seem to matter if the engine is warm or cold. If I am stopped at a light and start moving, the engine takes a bit of time to get up to speed. Mid-range and high-end speeds the engine is great and pretty snappy. I can get from 40 kmph to 160 kmph really quickly but up to 40 is a bit slow. Maybe it is just a heavy car and takes time to get up to speed.

I have been trying to find out what a particular window switch is for. It isn't in the owners manual. So I have four windows switches but there is a fifth one beside the front right window switch. Anyone know what this one is for? It doesn't do anything.

Well if anyone knows if these problems point to something in particular then I would be grateful for any advice. I am going to attack all the problems myself so

 

1) quite often, there is some de-lamination in the window and the coils fail, I imagine this likely is what happened here, take a multi meter and test to see if you're getting voltage at the back.

2) I bet a failed motor, again, multi meter to the connections and see if it's got voltage there. If it doesn't then you're gonna have to start tracing the wires. (It could also be a failed switch)

3) switch could be an issue, could also be the button on the door that is depressed upon opening the door.

4) i dunno about head rests, are they electric? or is it just a button? if it's a button, mash it in good! if it's electric, you guessed it, multi meter, see where the fault is

5) Rough idle, and slow pickup is not too hot. do a full fluid service, if that's not already been done, check your spark plugs, do they look dirty/are they gapped properly? wires/distributer are they okay? I don't know your engine I'm afraid, I DIY on the older generation 450 V8s. This could be a gasket problem, the engine could be breathing in and out wrong too. That last problem could be ANYTHING THOUGH, you're gonna have to start ruling things out I'm afraid.

 

Thanks Adrian, I will finally be able to get into looking into these problems this weekend, and figured I would be breaking out the electric tools to check things, but wasn't sure if there was a relay or something that might affect a few of these things. I will post back if I figure this stuff out.

 

I could be wrong on this as I don't have my manual handy but I believe the
5th window switch is to disable power to the rear power windows to prevent children from playing around with them while they are sitting in the back seat.

 

There is a small button that disables the back windows which is in between the front left switch, and the rear left switch. The switch I am asking about is actually between the front left switch and the front right switch. I can't find any info or pictures about it, and on my car, it doesn't seem to do anything. It even has a picture on it that is the same as the other window switches.

 

Back window - delaminating is very likely.
Check for "milkiness" at the edges of window.

Mirrors - only the passenger mirror is powered for a start.

Headrests - electrically powered - press and hold button. No motor, just magnetic coils I believe.

Interior Light- door switch is the likely culprit - either wear, or some later model switches had a second position that disables the light so it's not on while a technician has the door open, doing work.
Try pulling it in and out to see if there are two detente positions.

Switch on centre console could be pwr door lock/unlock switch.

In general, with all these issues, check battery and charging levels.


Check these things first. Good luck

 

You may have already found and fixed your problems as this is an older thread.
on "2" I have no thoughts.

1. This could be a bad relay (right side motor compartment) you'll get to it after you removed the fuse cover. There are 6 screws that undo the cover for those relay's underneath it.
The one in question is N10, which sits in the center about 2.5 inches long. This one may have bad connections inside the device. MB used a 1950's method to have them built. The contacts aren't soldered they're rather riveted. Prone to corrode in places that are hard to see. If you can you, it is possible to open the relay and solder the long contact stripes at the rivet point. The lower row is not possible to solder, no access.

3. This could be a failed combination relay N2/4. Unfortunately this sits behind the instrument cluster and the same has to be removed to gain access to it. The relay is the one that you'll see to the left straight looking into the cluster compartment. For my experience it will fail (burned trace) if the right door contact is shortened from _12V to ground. It will take out a rectifier diode and possibly burn off the trace attached to the diode. This prevents a current to flow that is needed to trigger the Dome Light. Easiest way to fix it, is to get a replacement that works, however check the door switches for shorts to chassis, before installing it.

4. In the center console is a toggle switch that releases the rear Head rests. Those are manually pulled into position and latch mechanically to protect the rear passenger in case of an rear end accident. The switch releases the head rest to fall back into default position, to extent the rear window view.

5. Sure hope not, however it could well be the throttle actuator wiring or worst the throttle's internal components e.g. the potentiometer that feeds back a signal to the ISC / ETM or the throttle flap clutch. Also the ICS could get a hit or two and decides to work marginally. This I don't know for sure and will have to have the previous problem resolved first to be sure.

If you haven't fixed all of your problems yet, above are some ideas.

 

2 rear-view mirrors won't move via the center console stick. The fuse seems to be fine but am not sure if there is anything else that might control this part.


I have been trying to find out what a particular window switch is for. It isn't in the owners manual. So I have four windows switches but there is a fifth one beside the front right window switch. Anyone know what this one is for? It doesn't do anything.


for 2, do you hear any sounds when when you try to move the mirror, it could be that the mirror it self is not attached well with the electric engine.in the middle console, is it a switch or something to scroll upward and forward. if it is a scroll it is for controlling the sound of the stereo between front speakers and the rear ones.