My first E30 DIY results in smoking parts

rammstein · 07-01-2009, 04:53 PM

I posted questions about what the hell to do next on 2 bmw boards, but basically there's a rear bulb check module that had gone bad (in theory) and all I did was put in a new one, and when I tested it, it didn't work and instead made that lovely electrical smoke. I have no idea where to go from here.... I guess I'm just venting here, but if any of you know E30s and there is some magic to this, I am all ears.

McLovin · 07-01-2009, 04:57 PM

Are you talking about the backlight bulb for the OBC?

bell · bell's Garage

were all the tail lights working? before you swapped the module?

my guess is the old module died the same way as the new one prividing there were lights out......if so...
it sounds like there is a direct short somewhere in the system, i would check the wires from the module to the bulbs, leave it unplugged and check all pins for continuity to ground, then start removing bulbs to see which wire it is (if it there's a short and the bulb is removed it'll still show ground on that wire) if it's not a faulty socket i'd be surprised, i've seen them overheat and melt causing a short........

rammstein · 07-01-2009, 05:20 PM

Quote:

Originally Posted by bell

were all the tail lights working? before you swapped the module?

my guess is the old module died the same way as the new one prividing there were lights out......if so...
it sounds like there is a direct short somewhere in the system, i would check the wires from the module to the bulbs, leave it unplugged and check all pins for continuity to ground, then start removing bulbs to see which wire it is (if it there's a short and the bulb is removed it'll still show ground on that wire) if it's not a faulty socket i'd be surprised, i've seen them overheat and melt causing a short........

Interesting. Yes, all the lights were working, even with the old module. That's the worst part- the stupid thing that's there to tell me if there is a problem is the only problem. The irony is not lost on me

So to do this check that you are suggesting, I assume it will be time to dust off my multimeter!!! What exactly should be done next? I am thinking in my head something like turn on the headlights to make all of the lights back there come on. Then, I think what you are suggesting is touching the red end of the multimeter to one of the pins, and the black end to a ground. Then I should be looking for something... I would think a zero, right? Any idea what sensitivity to set the multmeter to for something like this?

Forgive me, its been awhile since I worked on a car, and even back then it wasn't pretty.

Figures I'd get good help in OT before anywhere else.

javadog · 07-01-2009, 05:30 PM

Even though all of the bulbs work, you should make sure they are all the correct wattage. Often, a cheapo bulb from a generic auto parts store is used. Just because it fits doesn't mean the car will like it.

Having said that, I think you also have other issues.

JR

rammstein · 07-01-2009, 05:31 PM

Quote:

Originally Posted by javadog

Having said that, I think you also have other issues.
JR

What are you trying to imply?

bell · bell's Garage

Well if the lights were working then first I'd make sure it was an identicle module and that it was plugged in correctly.
Do check that the proper bulbs are installed......
With the bulbs plugged in they will show some continuity to ground with resistance, set your meter to ohms.....with the bulb out there should be no reading at all, this is providing the cirquit from the bulb to the module is a strait shot.
Does anyone have a schematic?
My friend tim has 2 e30 m3s.....I'll see if he can look at his manuals if we can't dig it up.

Rot 911 · 07-01-2009, 06:18 PM

Could be the same problem the E46's had. A bad ground system sets off the warning light even though all the lights work. Cure is to add an additional ground back at the rear lights. If you go to E46fanatics.com and search for tail light and ground the DIY will probably come up.

javadog · 07-01-2009, 06:18 PM

Quote:

Originally Posted by rammstein

What are you trying to imply?

Your new car be busted.

Or, I don't think cheapo bulbs can smoke a part like that.

JR

rammstein · 07-01-2009, 06:24 PM

Quote:

Originally Posted by bell

Well if the lights were working then first I'd make sure it was an identicle module and that it was plugged in correctly.

BMW designed the module to be impossible to install wrong- the harnesses can only fit in one way, so I'm pretty sure I didn't mess this up. Luckily I also have the old module to compare to, and it is identical

Do check that the proper bulbs are installed......
On my way out to check this now.

With the bulbs plugged in they will show some continuity to ground with resistance, set your meter to ohms.....with the bulb out there should be no reading at all, this is providing the cirquit from the bulb to the module is a strait shot.
Two problems with accomplishing this will be that I don't know which wires go to which bulbs, and second to pull out a bulb and test, the taillight back pulls out and removes it from the system altogether. It has like the equivalent of its own harness that disconnects when you pull out the bulb side- I've never seen anything like it before
Does anyone have a schematic?
My friend tim has 2 e30 m3s.....I'll see if he can look at his manuals if we can't dig it up.

Thanks for the help so far- I'll see about those bulbs now.

rammstein · 07:29 PM

I went out and wrote down the bulbs- there were four on each side and they had labels right on the panel for what they were supposed to be. Two were incorrect, and I need to look into that.

I also brought the module inside and popped out the circuitboard to see the damage. Check the attached pics- you can totally see the resistor that went kaput. The rest of the board looks ok, so when and if I figure out why so much juice was going to it and fix that, then I think I can go to radioshack and get a new resistor and have the wife help me solder it in (she knows how to do that). Its really stinky.

edit- nevermind about the bulbs bring incorrect- I checked it out, they are ok.

YTNUKLR · YTNUKLR's Garage

looks like you need some

Substitute for Bosch.

bell · bell's Garage

what do the traces on the bottom of the board look like? if the resistor popped it could've burned some traces too......
bad grounds can cause all sorts of problems, it's the one thing german electronics don't like.....

did the other module have the same failed resistor?

follow the traces on that resistor and see which plug pin it goes to, then see if you can identify which wire in the car it goes to, this will give some direction....resistors don't pop for no reason, and you said it....too much voltage...

just a thought.....since you have your meter out check the voltage at the battery when the engine is running......just to make sure it's not overcharging....

onewhippedpuppy · 07-02-2009, 03:51 AM

Probably not related to your problem, but clean every bulb contact with emery cloth, contact cleaner, and apply dielectric grease. I don't know what it is about BMW, but they all have issues with contact corrosion on the light sockets. I actually think it is the Germans, my C36 had the same issue.

rammstein · 07-02-2009, 06:28 AM

Quote:

Originally Posted by bell

what do the traces on the bottom of the board look like? if the resistor popped it could've burned some traces too......
bad grounds can cause all sorts of problems, it's the one thing german electronics don't like.....

did the other module have the same failed resistor?

I will check this when I get home this afternoon. Good idea.

follow the traces on that resistor and see which plug pin it goes to, then see if you can identify which wire in the car it goes to, this will give some direction....resistors don't pop for no reason, and you said it....too much voltage...
There is only one resistor on the board. I looked at the underside last night, albeit not super closely, and the traces looked ok, which is unfortunate in a way because if one was clearly fried it could steer me.

just a thought.....since you have your meter out check the voltage at the battery when the engine is running......just to make sure it's not overcharging....
Unlikely, but about 5 seconds to test, so I'll do it.

In addition, I need to find something that says what each blade on the harnesses is connected to. Then I need to do the continuity testing by touching one end of the multimeter to the blade, and the other to the end of what it connects to- if it doesn't beep, something is amiss, right?

rammstein · 07-02-2009, 06:39 AM

It appears I've found some excellent reading material for the toilet this morning:

http://www.armchair.mb.ca/~dave/BMW/e30/e30_91.pdf

rammstein · 07-02-2009, 09:58 AM

Here's what I've been able to deduce as far as what the acronyms on the module refer to:

KE - LH and RH Rear Side Marker Lights
54 -
58L - LH Front turn/park/sidemarker lights
58R - RH Front turn/park/sidemarker lights
54L -
54R -
58L1 - LH Rear taillight assembly
58R1 - RH Rear taillight assembly

KAL - Lefthand License Lights (in German I'm guessing 'Kennzeichen Auf Links')
KAR - Righthand License Lights
KKL - License PLate Fault Indicator (output to control unit)
31 - Ground for the Unit itself?
58KL - Rear Lights Fault Indicator (output to control Unit)
54KL -