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Discussion Starter #1
I have a 91 E34 M5 that I'm revamping the entire suspension. Making good progress so far, but my fuse 21 (charging socket) keeps blowing out, and as a result, my interior lights go out.

Any ideas??

Anyone knows what else is fuse 21 is connected to?
 

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According to the ETM, the following

FUSE 21 - 10A
Licence Plate / Trunk Light
Interior Lights
Glove Box / Cigar Lighter / Charging Socket
Anti-theft for Alpine car stereo

In my car the trunk light wire was severed by hinge mechanism for the lid.

The symptoms were no trunk light, but it could have just as easily been a blown fuse.

The ETM, claims the wire providing power to the trunk light Red/White (RT/WS)

Regards,

Reg.
 

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Discussion Starter #3
Thank you, but unfortunately, it keeps blowing the fuse, I suppose I need to check all that's listed above to see if anything is shorted? Any good way to check?
 

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Blowing Fuse

Does the fuse blow the second it is replaced ?
 

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Discussion Starter #5
No, when I replace it, all the interior lights work again, but then I don't know when it blows the fuse... seems like when I drive it for a few times, it blows it.

I'll swap it again, and let the car sit, see if it still blows it. Any ideas.?
 

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Determining the Problem.

Solving intermittent problems like this may take a while, so you're going to need to be patient as we step through this.

All wires from Fuse 21 are coloured Red (Rot) with a White (Weiss) stripe (Rt/Ws)

Here's a description of the circuit.

Fuse 21 >-rt/ws-> Join X207
X207 is in the Front Fuse Box.
Join X207 >-rt/ws-> Connector X15 Pin 22 >-rt/ws-> Charging Socket
Connector X15 is 30 pin, White and is located
"Below LH side of dash, near kick panel, left of the steering column"
Join X207 >-rt/ws-> Connector X14 Pin 16 >-rt/ws-> Join X435
Connector X14 is 30 pin, Yellow and is located
"Below LH side of dash, below driver footrest"
X435 looks like it is located beneath the rear seat in front of the rear fuse box.
Join X435 >-rt/ws-> Alpine Stereo Anti-Theft Module Pin 11
Anti-theft module is located "below LH rear seat"
Join X435 >-rt/ws-> Trunk Lid Switch
Trunk Lid switch is located "in centre of trunk lid in trunk latch assembly"
Join X435 >-rt/ws-> Connector X355 Pin 2 >-rt/ws-> Interior Rear Right Light
Connector X355 is 3 pin, White and in the RH C-Pillar
Join X435 >-rt/ws-> Connector X356 Pin 2 >-rt/ws-> Interior Rear Left Light
Connector X356 is 3 pin, White and in the LH C-Pillar
Connector X356 Pin 2 >-rt/ws-> Connector X336 Pin 2 >-rt/ws-> Front Dome Light
Connector X336 is 4 pin, White and located "In centre of windshield header" (up in the roof behind the panel that hides the sun roof motor)
I'm not sure what will happen if you disconnect the anti-theft module of the Alpine Stereo, so for the moment, I wouldn't that.

Try disconnecting each of the various interior lights, one at a time and see if the problem goes away. Sometimes when a globe fails, a broken piece of the element shorts across the 2 pieces of metal that normally support the element. Do you have an interior light that doesn't work ? This may be the problem.

Similarly, has the trunk light failed / try disconnecting the trunk light ?

I my "5", the connector for the charging socket is poorly protected (a piece of low density sponge). Has a bobby pin / paper clip or some other metallic foreign object fallen into this connector ? Try disconnecting it and see if the problem goes away. I think the Red/White cable plugs in to the back of charging connector.

Let me know how you go with all that and I'll see if I can think of a few more things to try in the mean time.

If none of that solves the problem, there's a distinct possibility that one of the wires in this circuit has compromised insultation. To blow a 10A on 12V circuit, the resistance from the appliance side (not the power side) of the fuse is going to be less than 1 ohm.
Do you have a multimeter to be able test this ?

Reg.
 

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Discussion Starter #7
So I finally have time to go into my car and test some of these, but still, no solution.

I removed all 3 bulbs (all working) in the trunk, as well as two bulbs in the rear (by the column), so only light remains are the three up front by the sunroof switch.

I replaced the fuse, and lights seem to work as usual, and remained working for a few days with car parked (I would open the door once in a while, to make sure it still works).

However, I drove the car yesterday, seem like shortly after I started the car, the fuse blown again, because my interior light won't work again... WTF???????????

Do you have a diagram or something you can send via PDF? this is bugging me, I would like to remove charging socket before doing anything else.

Solving intermittent problems like this may take a while, so you're going to need to be patient as we step through this.

All wires from Fuse 21 are coloured Red (Rot) with a White (Weiss) stripe (Rt/Ws)

Here's a description of the circuit.

Fuse 21 >-rt/ws-> Join X207
X207 is in the Front Fuse Box.
Join X207 >-rt/ws-> Connector X15 Pin 22 >-rt/ws-> Charging Socket
Connector X15 is 30 pin, White and is located
"Below LH side of dash, near kick panel, left of the steering column"
Join X207 >-rt/ws-> Connector X14 Pin 16 >-rt/ws-> Join X435
Connector X14 is 30 pin, Yellow and is located
"Below LH side of dash, below driver footrest"
X435 looks like it is located beneath the rear seat in front of the rear fuse box.
Join X435 >-rt/ws-> Alpine Stereo Anti-Theft Module Pin 11
Anti-theft module is located "below LH rear seat"
Join X435 >-rt/ws-> Trunk Lid Switch
Trunk Lid switch is located "in centre of trunk lid in trunk latch assembly"
Join X435 >-rt/ws-> Connector X355 Pin 2 >-rt/ws-> Interior Rear Right Light
Connector X355 is 3 pin, White and in the RH C-Pillar
Join X435 >-rt/ws-> Connector X356 Pin 2 >-rt/ws-> Interior Rear Left Light
Connector X356 is 3 pin, White and in the LH C-Pillar
Connector X356 Pin 2 >-rt/ws-> Connector X336 Pin 2 >-rt/ws-> Front Dome Light
Connector X336 is 4 pin, White and located "In centre of windshield header" (up in the roof behind the panel that hides the sun roof motor)
I'm not sure what will happen if you disconnect the anti-theft module of the Alpine Stereo, so for the moment, I wouldn't that.

Try disconnecting each of the various interior lights, one at a time and see if the problem goes away. Sometimes when a globe fails, a broken piece of the element shorts across the 2 pieces of metal that normally support the element. Do you have an interior light that doesn't work ? This may be the problem.

Similarly, has the trunk light failed / try disconnecting the trunk light ?

I my "5", the connector for the charging socket is poorly protected (a piece of low density sponge). Has a bobby pin / paper clip or some other metallic foreign object fallen into this connector ? Try disconnecting it and see if the problem goes away. I think the Red/White cable plugs in to the back of charging connector.

Let me know how you go with all that and I'll see if I can think of a few more things to try in the mean time.

If none of that solves the problem, there's a distinct possibility that one of the wires in this circuit has compromised insultation. To blow a 10A on 12V circuit, the resistance from the appliance side (not the power side) of the fuse is going to be less than 1 ohm.
Do you have a multimeter to be able test this ?

Reg.
 

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I would once again suggest checking the wiring to the trunk lid. As removing the bulbs wont help if a live wire comes in direct contact with the ground at the hinges.

Sakke
 

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Discussion Starter #9
I will pick up more fuses today, and see if I could duplicate this with opening and closing of the trunk, leaving car engine off... if I could, then we found the problem... question will then be, how to fix it...

first things first.

was wondering if you had a diagram that led you to all the previous very useful instructions and comments.

Chino

I would once again suggest checking the wiring to the trunk lid. As removing the bulbs wont help if a live wire comes in direct contact with the ground at the hinges.

Sakke
 

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I will pick up more fuses today, and see if I could duplicate this with opening and closing of the trunk, leaving car engine off... if I could, then we found the problem... question will then be, how to fix it...

first things first.

was wondering if you had a diagram that led you to all the previous very useful instructions and comments.

Chino
Nope, just 6,5 years of ownership. Hope there is somebody else who can provide you with one.
There is the BMW TIS workshop manual freely downloadable here somewhere (1500pages) that im sure contains all the instructions and diagrams needed, I can look it up for you....

:cheers:
Sakke
 

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Is the TIS the right answer & how well can you solder or crimp ?

Hi all.

I have not had such a great experience with the TIS, I found it very limiting. This maybe because I haven't found out how to navigate it properly. My personal preference is the ETM (Electric Troubleshooting Manual). The name is misleading. There is very little troubleshooting info in it, but it does have incredibly detailed wiring diagrams and location information. It is the source of all info I have provided you date. The document is protected against copying, but there are bound to be illegal copies on the web, if you're OK with that. In some countries you can actually buy it from BMW. Alternately, the Bentley manual has reasonably accurate circuit diagrams, but it does not seem to have all combinations listed in the ETM.

I suggest you need to hunt down a Bentley manual or ETM (or TIS if it has wiring diagrams) before proceeding. Having a picture of what you're trying to fix will make the task much easier.

Dr Sakke is also very right when he says removing the globes won't help if they haven't failed as I detailed above, or if one of the Red & White wires has compromised insulation, and right now, that's what it looks like. It sounds lke some movement somewhere causes an exposed wire to come in contact with the body somewhere. One of those Red & White wires may have a crack or wear-through in the insulation that is causing a short circuit and subsequently blows the fuse.

The first step is to try identify those wires and check them for cracks or wear marks. Plainly this is not practical for whole length of all of those wires. It will take a fair bit of effort to remove all the trim required to follow all those wires from start to finish.

Checking the boot (trunk) lights is probably easiest, because removing all that trim is fairly easy and there is a fair bit of light available to check the insulation. As I said earlier, the cables in behind the plastic cover on the left hand boot hinge have been cut in my car. So remove that cover, see if you can see any Red/White wires and give it/them a very thorough check for cracks, nicks or wear marks in the insulation. If the boot light cable is a problem and it runs behind this cover, I'll bet you any money, this is where the insulation fault will be.

If physical checks seem too daunting, to proceed any further, you need to be able to use a soldering iron or wire joining crimp tool, because we are going to have to cut some wires from some of the joins detailed above, to find which one is the cause of the problem. Unless you are confident in being able to restore those connections properly and protect the joins properly, (and that doesn't mean wrapping electricians tape around the solder joins, it means using heatshrink), I suggest you may need to consider professional help.

Let me know what you want do.

Regards,

Reg.
 
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Discussion Starter #13
Problem FOUND....!!!

Left trunk arm, there's a wrapped cable.. if you trace it, I have about 10 cracked wires there, 4 of them broke off... nasty. Time to crimp them one by one...any idea what gauge crimp I need to get?
 

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I can help.

If you give me your VIN and the colour of the wires with the faults, I may be able to give you the wire dimensions.

The ETM provides dimension info next to each cable. For instance, the Red/White wire going to the trunk light has "0.5" written next to it. This cable has a cross sectional area of 0.5 square mm. That means the cable is about 0.8mm [(area/PI)^0.5*2 in Excel speak] in diameter or about 31 thou (0.8/25.4). 20 AWG is about 32 thou.

http://www.powerstream.com/Wire_Size.htm

The next biggest commonly used wire seems to have a cross-sectional area of 0.75 sq. mm. This is about 18AWG.

Hope that helps,

Reg.
 

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Discussion Starter #15
Done... crimped about 4~5 cables, some actually have different diameter. Taped every cable individually, short fixed...

Thanks to E34 nut and others for your help.
 
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