Dash & Console lights wont turn off, + more - PeachParts Mercedes-Benz Forum

Veloce300DT · #1 07-16-2006, 05:08 PM

WHOA I relaized my original post was a little too confusing and detailed. heres a simplified version.

Dashboard instrument cluster lights, and console lights stay on all the time when the ignition key is turned on, irregardless of wether the headlight switch is off, on, or in any of the parking light modes.

Windows stopped working all at once- drivers window is stuck down.

When I press on the drivers window button, the dash lights go out, and when I release the button they come back on.

I pulled the console to check for any loose connections, all seem fine. All of the console buttons were working fine prior to these problems, so I highly doubt that they all went bad.

The cluster and dash light problem happened first, then an hour or so later the windows stopped working.

Im guessing its a fuse?

HELP!!!! where do I look next?

86560SEL · #2 07-16-2006, 11:02 PM

Sounds like an electrical short in your wiring system, or perhaps a relay? I had a BMW 7-Series (1982) that had console lights that would not turn off. I had to keep the battery disconnected
Which Mercedes has the fritz? The 1984, or the 1996.5?

Veloce300DT · #3 07-17-2006, 12:52 AM

These problems are occuring on the 84 300D. It has been brought to my attn. that the window problem may have been caused by a bad "Ice Cube" relay, which resides behind the instrument cluster.

I'll be looking into the problem more tomorrow and tuesday when I have more time on my hands.

Any further information and advice is always appreciated!

Jeremy5848 · #4 07-17-2006, 01:45 AM

Nate,

If the problem remains unsolved after you investigate that relay, maybe some additional information from you will help us with the diagnosis. I agree with the theories advanced so far -- a short of some sort. I'm wading through the schematics in my manual, trying to find something in common with your description.

Tell us what in the electrical system works and doesn't work. You've already told us that the dash lights are on with the 'ignition' switch and the windows won't work at all. When the dash lights are on, are the tail lights and running lights also on? Will the car start and run? Does the radio work? The heater and a/c? What happens when you turn the headlights on? Do the brake lights work? Turn signals? Sunroof?

Check all the fuses. Remove, clean, replace each fuse. Check for corrosion causing a bad connection through a fuse. Let us know.

Jeremy

Veloce300DT · #5 07-17-2006, 02:18 AM

I just went down to the garage to double check everything.

The dashboard lights DO NOT come on anymore with the ignition. This problem has strangely gone away. When they were coming on with the ignition, NONE of the exterior lights turned on, only the dash lights. The dimmer does need to be cleaned- it takes a very light touch to adjust it to its maximum brightness if it has been tampered with, but that has been like that for months.

The car does start and run excellently.

The radio works.

The A/C works exceptionally well. Nice and COLD. Fan speeds work properly as well. Its hard to tell if the heat works because it is HOT here, 100 degree ambient temperature in the day, and a warm balmy 80 degrees at night. But I suspect it works fine.. warm air blows strongly with the heater turned on, but the air is warm anyways with just the vent open since it is so hot out.
The climate control unit is 2 years old. I had the original unit replaced with a new one when the A/C system was gone over- R134A conversion, new expansion tank, compressor, thermostat, fan clutch, etc...

When I turn the headlights on, they come on along with the tail lights, license plate lights, and front corners as they should. The individual settings for just parking lights for both sides, or just the L or R sides work as well.

The turn signals work fine as well... and the indicators on the instrument
cluster inside the car work as they should.

Brake lights work as they should with brake pedal depressed.

Reverse lights work.

Hazard lights work, and console button lights up and flashes properly.

Sunroof opens and closes quick and smooth.

It now seems that the only things not working properly on the car are the windows. They still do not go up and down. But it also scares me a little bit that the dashboard light problem of them coming on with the ignition switch has solved itself.

I'll get back to you guys after I have investigated further. Thanks for the support Jeremy!

Jeremy5848 · #6 07-18-2006, 01:27 AM

Nate, you are wise to be concerned. Problems that go away by themselves often come back by themselves. However, now that you have checked out a lot of the electrical system, let's concentrate on the windows. First, make sure the fuses (there are two, as I recall, one for each pair of diagonally opposite windows. Mercedes designed it that way so that you could get one front and one rear window to work even if one fuse blew. The fuses are "a" and "b" in the fuse panel.)

Unless both fuses blew at once, which is possible but unlikely, the problem may be in the relay that controls power to the windows. This relay switches on with the 'ignition' and carries the heavy current that the windows draw. I don't know where this relay is -- sounds like someone has told you about it -- and lack the proper manuals. A quick search of this forum and I think the relay is behind the instrument cluster. How to recognize it is another question.

One simple test that I ran across: turn the 'ignition' on and wait until the glow plug timer has cycled -- usually about 30 seconds after the glow plug light turns off (if you're in a quiet location, you'll even be able to here the 'twang' of the relay cutting out). Now flip the dome light switch so the dome light is on. Then try the window switches and watch the dome light to see if it dims. If it does, something is drawing current. If not, then the windows are not drawing any current so no voltage is getting to them. You can experiment with the sunroof (if you have one and it works) to see how much dimming to expect.

Another possible cause is the fuse through which the relay itself is powered. In the diagram in my Haynes manual, this is fuse 2. Fuse 2 powers the dome lamp, the trunk lamp, the power antenna, and a bunch of other stuff. If all that stuff works, fuse 2 is good. If you can find the window relay, you should be able to cycle the ignition switch and hear and feel the relay turn on and off. If it doesn't work, the windows won't get power. Even if the relay works, its inner contacts may be burned from carrying power for many years.

There are several relays in your car that appear to be the same kind -- the aux fan relay and the air conditioner relay, to name two. You may be able to swap just to see if it helps. The relay is in any case very common -- all the foreign car parts places should have them.

Jeremy

dmorrison · #7 07-18-2006, 03:50 AM

Looked at all the schematics for the electrical system and besides a short. I don't see any common ground except the following.
An alternator spike caused a couple of problems. It shorted out the window relay in the engine compartment causing the windows to fail and the spike caused the headlight switch to short or arc causing the headlight switch to keep the cluster lights on.

Also check the #14 fuse for a blown fuse to the window relay.

This is the only common thread I can figure.

It may be in left field but I don't see acommon connection between the 2. Unless its a short.

Dave