Please explain why you continue to mention a relay. Not that I have fully assessed it, but it seems unlikely that your problem is associated with a device that turns one circuit on when activated by another circuit.

 

Because it seems like it was flickering on and off before, and it is like the circuit is stuck "on" now. I have heard that when relays get quite hot, they can 'weld' themselves to the on position over time. I'm not so experienced with electronics so please excuse me if I'm coming off as ignorant. I can't think of many things that would cause a circuit to remain on when it's powered off.

Thanks for your reply and your concern! I'm still learning

 

I ask because as I understand it, your circuit only seems to get hot when the car is off. Is that right? I am not arguing with the point as much as just trying to understand what you are actually experiencing. Since the wiring from the TSB is apparently not the issue, I wouldget to the dash dimmer module and do some voltage readings both off and on.

 

I smell some slight electrical burning or melting--this only happens when the lights are switched off, car running or not. It gets noticeable when I leave the car parked for, say, half an hour with the fuse plugged in, or if I'm driving in the daytime with the fuse in.

The dimmer module on the steering column, right? I can try that, though I'm not sure what readings to look for, etc. Not sure if it's worth mentioning but the dimmer switch still works; I can still adjust the dash lights when switched on.

Thanks Ross.

EDIT: I also just remembered that when the car is off and the light switch is on, only the passenger side headlight comes on. It's been like this since I got the car--anything to worry about/possibly related? Very weird indeed..

 

You have a digital multimeter, right? 12 volt test light?

 

Yes I do. Where should I put the rods and at what setting should it be?
(I feel like such a newbie!)

Thanks

 

Give me a day or two - I am not at the computer that has the diagrams. i will write up a short step by step.

 

Thank you very much, Ross! please take your time!

 

A new little tidbit... I can clearly hear humming in the speakers when my volume is down, especall from the front left speaker under the windshield; this happens to be the place where I'm pretty sure the slight burning smell comes from.There's definitely a bad ground somewhere; is there one located behind the dash or would the engine bay be a better bet?

Thanks everyone.

 

check your BCM (Body control module, Body processor Unit)

 

Since your symptoms do not SEEM to be all related, lets make sure we have all of them in one list. Please check it for accuracy:
Symptoms:
1. Lights on 1) radio and 2)window controls stay on
2. Dash lights are apparently on, but dim when lights in #1 stay on
3. Lights in #1 don’t come on sometimes
4. New report that in addition to #1 and #2 lights, 3) garage door opener, and 4) sunroof lamps stay lit
5. Heater stopped blowing warm
6. Battery discharges
7. Wiring is boot is frayed, and not repaired, then later repaired
8. Car has burning smell
9. 10 amp fuse #2 in LH heel box stops battery drain
10. With headlight switch on, and car switched off, RH headlight stays on (Are you sure left headlight comes on when car is not switched off?)
11. Humming heard in speaker (I assume this is only with car on and running)

Are these the current situation? Myguess is that #1, 2, 3, 4 6, & 9 and maybe 8 are related. I believe #11 is a result of a low battery causing high charge current. I suspect #5, 7, and 10 are not related.

Can you or have you gotten to the dimmer module yet? I don't remember what you need to do to get to it.

 

1. The backlights for the keys are illuminated on the radio, but NOT the LCDs. The same goes for the climate control and clock. So basically, anything controlled by the light/dimmer switch and NOT the photosensor.

2. The dash lights are very dim, probably about as dim as they would be if you turned the dimmer all the way down--maybe dimmer. This is only when the lights are switched off; with the switch on, I have full control and there are no issues.

3. I used to have a problem with these lights flickering, and sometimes not even coming on at all. Now, they are on 100% of the time that the fuse is plugged in, and have never flickered since they were stuck on.

4. True.

5. I have ordered new brushes for it and I doubt it is related, but I will double check once I install the new brushes.

6. It drains very quickly with the fuse plugged in. I have trouble starting the car after just a few hours, and the battery gauge will show around 9 at that time. It usually reads about 11-12 when the car is parked and I switch to the "on" position. I have used a multimeter just after parking and it showed 12.8, IIRC. I have a fairly slow crank if the car is parked more than 8 hours or so and it is cold, e.g. the morning, and I have yet to test the voltage with a multimeter after the car has sat overnight. However, this may be the starter motor.

7. I have repaired it, yes. Everything is currently working, including the key fob now.

8. This only happens when the fuse is plugged in and the light switch is set to "off". It's especially noticeable if I park for a short period of time without pulling the fuse. Smells like that "new plastic" smell, very weird, and it must be burning though I have never seen smoke.

9. Correct, thought I will have to test whether the drain is 100% stopped. I have left the car for two days and it still was able to start, so I doubt it has any significant drain.

10. I'm sure that both headlights are on when the car is on. Since I got the car, though, I've noticed that if I leave the lights on when the car is off, just the passenger side headlight stays on--is it supposed to be off, or is the driver's side supposed to stay on?

11. I will double check that it's only when the car is running (alternator, right?). It's only noticeable when the volume is low, and I definitely hear a bit of feedback when revving the engine unless the volume is cranked way up. This humming sounds exactly like when you go to plug in a guitar and touch the patch cord to its outlet, though not very loud.

I have heard that #11 could be a bad ground, though I have pulled out the ski slope and found none. Just last night, I took out all the trunk carpeting (not as difficult as one would think), so I could check all the grounds there. Nothing was loose or dirty at all. The antenna was fine, too. I guess that leaves the engine bay--are there any located behind the dash? I will double check all the fuse boxes.

Last night, I also cleaned the battery which had a small leak at some point. I cleaned all the corrosion under it with baking soda and water. The indicator is still black, not white which would indicate a battery that needs replacing; is it possible that it is still bad? I could not open the cover and did not want to risk damaging it; I am unsure whether my battery is sealed for life (it's the correct long battery, and it's actually a Mercedes one) or if I could top up the cells. There appears to be a thin cover spanning the length of it, but I couldn't pry it open and it mentions nothing about cells being located under it.

Thank you so much for your assistance! I hope this post clears things up. I will continue to investigate today, though the only place I haven't torn up yet is the dashboard.

 

How do I go about checking this?

I will update this post with some more pictures shortly. I just realized the ones I took on my phone aren't helpful at all.

Edit: here are the pictures




One empty cluster of wires and one single unconnected wire.





Two unconnected clusters of wires?





A random tube with no wires.


Is any of this abnormal? I have no idea what the tube is for. It was sitting behind the battery. I'm assuming the wires were for an omitted accessory, such as a car phone (I found a telephone jack under the ski slope, too) but I want to be sure nothing is missing.

 

Just one more question- Can you get to the dimmer module? I believe it is part of the column.

 

I'm sure I can. Worst case scenario, I'll get to it when I take off the entire dashboard. I'm assuming I just have to remove the underscuttle of the steering column.

I've taken apart the rest of the interior- the rear seats, the backs of the front seats, the ski slope and arm rest, the trunk carpeting, and the door panels, so I'm very comfortable with the car now.

 

So, the dash lights are only controlled by the light switch signalling the dimmer module, as you can see in the attached schematic. The dimmer apparently gets the command to turn on from the "side lamps" switch below it, and it then supplies power to the entire group of dash lights on one circuit. Its power comes from the LH heelboard fuse you identified earlier.
That means that either your problems with the headlamps, the heater and the original boot wiring damage are not related OR there is a wire harness shorting between two circuits. To isolate that, you need to simply pull the connector from the dimmer, then put the fuse back in and assure the lamps are off. If the lamps are off with the dimmer unplugged, we will plug it back in and measure the voltage to ground with the fuse in and the light switch off then on. I would say the likelihood of the dimmer module being the culprit for your problem is high, but lets test it first!

BTW, the going rate for a module seems to be less that $40.00 on fleabay. You can probably do much better than that since we seldom hear of any problem with one around here.
http://www.ebay.com/itm/like/2316785...chn=ps&lpid=82

 

Now to the headlamps story! From the attached diagram, you can see that both of the "main" or lowbeam headlamps are on the same circuit. If the relay is on, they should both be on. If the relay is off, they should be off. FOR SURE! So, I do not doubt your observation (well maybe a little?) but if you are correct and the main headlamps are not both on or both off, then you absolutely have a wiring error. Either something has been modified or two wires (or several) in a harness are shorted together. Or the boot wiring is crossed up somehow. The other possibility is that the ground on one side is loose and the dip (highbeam) circuit is creating a back voltage. Have someone help you and be absolutely sure what you are seeing for the low and high beams, engine running and off.

 

Ross, you're the best. Seriously!

I'll try unplugging the dimmer module and putting the fuse back in. I don't think the boot or heater have anything to do with my problem, but the brushes won't get to my house for another week so there's no way for me to be sure! At least I've outruled any damage to the wires or grounds in the trunk (including all the ones under the carpeting), and under the ski slope. I have an exam tomorrow, so I'll most likely be doing this Wednesday or Thursday.

As for the headlights, I am 100% certain. I can take pictures if you wish. They definitely work when the car is on, and the driver's side won't illuminate if the car is off and the light switch is on. When I activate the headlamp convenience feature by pressing the lock button on my fob twice, they both come on. This was a problem even when the boot had one measly wire connected with all the rest completely frayed. Could this be related to my "burnt bulb" dash light? I suspect the sensor (or whatever the second plug is in the main beams) has gone bad, since it looked kind of ratty IIRC. The dash light is usually on but sometimes illuminates only faintly, and all four lights in my trunk are now working so I can rule those out. Very strange. The only thing I can think of is that I have no hood light; surely our cars were fitted with one, but I can't even see where mine would be!

I hope all these problems aren't from a bum battery. I don't have an appropriate replacement to test out. I have recently started getting the SRS warning light, for example, which I have heard is something like the kiss of death for the battery. The reading on it is still good, though...

I will get back to you when I have a chance to disconnect the dimmer module. Thank you so much!

 

To test the headlights, you need to measure the voltage on the U/W wire- the one that is purple with a white stripe- for each headlamp connector when the car is off and the switch is on. Then measure the B or black wire on the other side of the same connector. Although there are differences in the lamp operation for different countries, I am pretty sure your lamps should be off in that condition. So, we will be looking for how stray voltage is getting to that connector.

 

Okay, makes sense. I will try that as well when I do the dimmer switch. Thanks!