1995 E320 Electronic problems

[EthanH]

OK, a little background....the central control unit in my 1995 E320 died last spring, and I had a new one installed to the tune of $3000. After working perfectly for about 6 months, the ASR light started coming on and the "check engine" light wouldn't turn off, even with the car turned off (exactly the same symptoms it had prior to burning out the first time.)

I took it back to the dealer and they said that water was getting in there, so they disassembled it, dried it out, wrapped it in plastic (inside and out), and reformed and sealed the plastic dust cover to keep water out (and all for no charge.)

OK, now the current problem: the "bulb out" indicator light keeps coming on, even though there are no lights out on the car. Is this possibly also related to moisture in the control unit? If so, how can I permanently fix this, as it's getting annoying, and I don't really want to replace another of these $3000 parts.

If not, any idea on what might be causing the new issue? Thanks in advance for any help!
---Ethan

[ILUVMILS]

Originally Posted by EthanH

......I took it back to the dealer and they said that water was getting in there, so they disassembled it, dried it out, wrapped it in plastic (inside and out), and reformed and sealed the plastic dust cover to keep water out (and all for no charge.)

No way! Really? You're kidding, right? A Mercedes Benz dealer did something for you, and didn't charge you? That's absolutely outrageous. Beyond comprehension. Unacceptable. If the other MB dealers' find out about this, your dealer will most certainly be brought up on charges. At the very least, they'll be forced to pay a heavy fine. I'd sure hate to be the Shop Foreman at that place. What the hell were they thinking??? After all, don't MB dealers have a reputation to uphold?

Now, getting to your lights. Take a quick look for any discolored bulbs. Start with the taillights. Replace any bulbs that appear to have darkened. Don't forget the license plate bulbs.

[nissanzx1]

Hi Ethan- Do you know if your car has it's original engine wiring harness? In case you did not know, the originals are faulty and must be replaced sooner or later as the insulation around the wires rots from heat in the engine compartment. This wiring problem can manifest itself by all kind of electrical weirdness, idiot lights like check engine, etc.

Your problem with the bulb out indicator may or may not be tied directly with the wiring harness, but you should inspect your harness for cracked insulation around sensor connections under your hood.

The harness is about a $1000 part, many guys do it themselves--It's supposed to be relatively simple if you approach it one connector at a time. I'm going to have to do mine in the next few months

Some mechanics will not attempt to trouble shoot your model and year MBZ unless the harness has been replaced...In your case, I would double check all exterior lights (even third brake and license plate lights as well as all side markers) as well as all the applicable fuses (simple stuff). You might check each bulb socket to rule out moisture problems.

Let us know what you find.

Good Luck,

-GH

[EthanH]

Thankfully the original wiring harness was replaced by a previous owner. There's at least one ancillary run of 3 or four wires that definitely still needs replacing, but the hard work is done.
Thanks for the tips! I'll start investigating systematically and let you know what I find!
--Ethan

[deanyel]

Does the bulb warning light come on a) when you tap the brake pedal, b) when you turn on the lights, or c) when you start the car (without touching the brake pedal)?

[radioguy]

My wife's wagon had a similar issue a couple of times. The first time it was a headlight bulb that was almost blown (it would work if you tapped it). The other time it was a blown license plate bulb (the use the same bulbs as the dome lights). The tail lights are also a bit buggy. I've had to remove those and clean/grease the contacts a few times.

Todd

[spit64]

Check if the bulb has the same size in Watt if you change one recently you might put a bulb with another Watt size thats why the warning light will light.

[Arthur Dalton]

Originally Posted by spit64

Check if the bulb has the same size in Watt if you change one recently you might put a bulb with another Watt size thats why the warning light will light.

...along with that suggestion, it is also recommended that matching lamps also be the same Manufacture/ Brand... ie., a matched set. The lamp warning module monitors lamp resitance and using different brands can trigger the lamp fault...

[EthanH]

Haven't changed any bulbs since I bought the car 2 years ago. As for when it comes on: it sometimes (but not always) comes on when I first start the car (whether the lights are on or not). If it's not on at startup, I can turn on the headlights and tap the brake pedal and it still won't turn on. Then it seems to come on either when I first move the transmission lever (I mean like a half inch, to get ready to pull it down into reverse), or just on its own after a couple of seconds, I'm not sure. Anyway, I may have time today to take a closer look at some of the bulbs, so I'll start there. Maybe something's a little corroded and adding resistance.....
---Ethan

[spit64]

Originally Posted by EthanH

Haven't changed any bulbs since I bought the car 2 years ago. As for when it comes on: it sometimes (but not always) comes on when I first start the car (whether the lights are on or not). If it's not on at startup, I can turn on the headlights and tap the brake pedal and it still won't turn on. Then it seems to come on either when I first move the transmission lever (I mean like a half inch, to get ready to pull it down into reverse), or just on its own after a couple of seconds, I'm not sure. Anyway, I may have time today to take a closer look at some of the bulbs, so I'll start there. Maybe something's a little corroded and adding resistance.....
---Ethan

Maybe the wiring to the reverse light

[torkydzl]

I had the same issue on my 95 wagon. It turned out to be a failing turn signal/hazard relay which plugs in behind the fuse box by the fire wall. Easy to install and costs about $160 from the dealer. Part no. 201 821 02 47