impossible bad luck - 1991 535i auto.

[M Malaviya]

Hey guys,

The Alpine stereo stopped working, checked the fuse in the engine bay - no problem; so checked for voltage on the red & yellow wires on the back of the stereo. Red wire has feed, yellow wire no feed. Checked the fuses under the back seat, number 38 (I think 30A) was cooked. Changed that and put everything back together. Now the car will not start, no spark at the coil. I admit to being a complete novice at electrics, so would very much appreciate any helpful hints on what to do next. Quite scared that I'll do more harm, without guidance, so apologies in advance if the gurus here think there is not enough information provided.

,

Mal.

[Felixdacat]

I think the yellow wire is the ignition wire. This will get a 12v feed when the ignition is turned on. If you blew a fuse, check all the wires behind the knee panel below your steering wheel. You may have a shorted wire. If no wires are shorted, maybe a bad ignition?

Good luck, Felix

[M Malaviya]

Felix - thanks for your input.

BTW a little more info. The PO (6 years ago) had told me that the alarm needed to be disconnected because the siren had caused problems. I do not have key-less entry, and have never considered getting the alarm fixed.

I am at present looking at the mess of wires under the back seat, and found a wire in a block connector attached to a slimline alarm module (?) that has obviously been shorted. When I disconnected the block-connector, the hazards blinked for about 10 seconds, adds to more confusion.

I am in the very very slow process of tracing the shorted wire backwards through one of the wiring looms - what a pain! At present, cannot really decide which is more of a pain - the wife nagging why it is taking so long, or the seemingly over-engineered car!!

I dread the thought that the trace-back may end up under the steering / ignition area, because it may involve getting behind the dash, which I have not done before. Still have absolutely no idea what could have caused the short in the first place, all I did was replace a 30A fuse!!

At the present rate, I'll probably be able to report back in a couple of years - fingers crossed!!

[Felixdacat]

Tracing shorts is a long process. A fuse will only blow when a direct short occurs, or when too much load is drawn. Did the fuse blow again when replaced? I'll look to see if I can Help. I have an 89 535i. I don't know if I have the same wiring. Check back soon

[laguner]

When you perform electrical work you must always disconnect the battery or you can cook the ECM. If you blew a fuse, you have a short. If you have a voltmeter on the fuse that blew and touch the other fuses with the battery disconnected you may be able to determine what two circuits are shorted. I would start by just tracing the yellow and red wires back and look for exposed wire. Another option is to connect something else to the 12v for the radio and use a different ground than the yellow wire. This will eliminate the radio as having an internal short. Without the battery connected the yellow and red wire should not be shorted-0 resistance or 0 volts between them. By the way, it was already asked if the fuse blew when the new one was inserted. Did it blow?

[genphreak]

Do the wipers, sunroof, windows and courtesy lights still work ok? Try removing the alarm module altogether until this problem is sorted. Did F30 blow again or could you have accidentally shorted it messing with the stereo? No point hcasing a problem you don't have. Wives are often painful. Cars however are only a pain until they work again...

[M Malaviya]

Tracing shorts is a long process. A fuse will only blow when a direct short occurs, or when too much load is drawn. Did the fuse blow again when replaced? I'll look to see if I can Help. I have an 89 535i. I don't know if I have the same wiring. Check back soon

Felix,

Appreciate your help. The replaced fuse has not blown. The battery has been disconnected, while I trace back the exposed wire......but it won't be until Tuesday that I get a chance to make a lame excuse not to go to work, need a day off to work on the car again. Gave myself the weekend off from the car. Will keep you guys posted.

[M Malaviya]

When you perform electrical work you must always disconnect the battery or you can cook the ECM. If you blew a fuse, you have a short. If you have a voltmeter on the fuse that blew and touch the other fuses with the battery disconnected you may be able to determine what two circuits are shorted. I would start by just tracing the yellow and red wires back and look for exposed wire. Another option is to connect something else to the 12v for the radio and use a different ground than the yellow wire. This will eliminate the radio as having an internal short. Without the battery connected the yellow and red wire should not be shorted-0 resistance or 0 volts between them. By the way, it was already asked if the fuse blew when the new one was inserted. Did it blow?

thanks for your input Laguner.
The exposed wire 9from under the back seat) is being traced backwards (see my reply to felix). BTW I am not sure the yellow wire is a ground, it is the ignition feed? also, the new fuse has not blown.....more in a couple of days......

[M Malaviya]

Whoopie!!!!!!

Managed to sort out the problem re shorted wire. Traced it all the way back to the alarm siren which the PO had taped over and left dangling just on the side of the engine department fuse-box. the insulation tape had weathered and an exposed wire must have earthed the body. Tha solution was to take out the entire alarm related loom and bin it. Bingo, the car started no problem. Thanks for all the tips guys, really appreciate your time.

On another matter, I had asked the forum recently if anyone had used magnecor wires. I considered the replies then, and for what it was worth, I decided to try these wires anyway (8mm blue). Wow, what a result - the car feels a lot crisper - almost like it has had a shot of steroids!! The spark delivered is visibly fatter than the bosche wires. Response on acceleration is markedly instanteneous. I thoroughly recommend these wires - just make sure you order a set with number 6 wire having the pick-up sensor already in place. I found mine dirt cheap from Apex Performance (special offer $59 + shipping).

On a sad note, one of the neighbours passed away about 3 months ago, and left his non-cat M-tec 535i (1989, owned from new, metallic grey, 46k miles, always garaged, full M-tec black leather recaro interior, manual, and pristine condition, but with metrix wheels) to his son, who does not care much about cars anyway (avid environmentalist), but for sentimental reasons, wants to keep it for the time-being. What a waste!! He has promised me first refusal if he decides to sell. I am keeping my fingers crossed.

[Felixdacat]

Great job dude. Its was a pain in the arse though. A little time and patience will solve many problems. Once again great job.
I'll give the Magnecor wires a try. Somebody else has to test these things out also.