blown fuse 21

CWY_M5 · 13th May 2008, 18:05

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?

E34_nut · 14th May 2008, 16:18

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.

CWY_M5 · 21st May 2008, 20:26

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?

E34_nut · 21st May 2008, 21:49

Does the fuse blow the second it is replaced ?

CWY_M5 · 22nd May 2008, 00:04

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.?

E34_nut · 22nd May 2008, 09:25

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.

CWY_M5 · 30th June 2008, 22:13

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.

Quote:

Originally Posted by E34_nut

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.

DrSakke · 30th June 2008, 23:21

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

CWY_M5 · 1st July 2008, 01:27

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

Quote:

Originally Posted by DrSakke

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

DrSakke · 1st July 2008, 08:31

Quote:

Originally Posted by CWY_M5

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....

Sakke