Think I have a major electrical problem

[justin_cosgrove 4]

I have a big problem with my e30.

The other day I was going round a round-a-bout when the car completely died, just like the batery had been disconected. I couldn't even put on the hazard lights and I was stuck in the middle of the road. Sombody stoped to help and as he was getting into position to try jump starting the car I heard the alarm arm itself, all power was back and the car started and run fine.

Two days later going to work car completely dies and coasts to a stop. I disconected the battery, re connected it and the car fired right up. this happened three times during the 5km trip.

Four hours later going home for lunch. I get 300 meters and it happens again, exept this time error is flashing on the dash, brake light warning light, and oil level warning lights on the overhead display light up. I also seen the 'over heat' light flash a few times. BTW it was reading below half way on the temp gauge. It continued to stop repeatedly on the way home, exept this time the engine would stop but all the dash lights and all power remained. I just turned the ignition off and then on again and the car started fine. Comming up to my house I felt the engine die for a second and then continue running. When running the engine sounds fine. I just checked everything I could think of and all I could find was the alternator belt was a little slack.

Basicaly I need at the very least ideas.

[_Matt_ 42]

Check the appropriate relays?

[justin_cosgrove 4]

Check the appropriate relays?

excuse my ignorance but where are they located? and how do I test them?

[_Matt_ 42]

You're looking for this,

You might want one of these too

http://www.amazon.com/BMW-E30-Service-Manu...0/dp/0837603250

Edited March 15, 2012 by _Matt_

[Ahmedsinc 414]

http://www.bimmersport.co.nz/forums/index....showtopic=21815

Fusebox and relay setout for E30s

Is there a fusible link for the +12v from the battery? If so check for good clean connections with no corrosion or degradation of the link, corrosion, wobbly cables or such - same applies for the main earth from the battery and the engine earth strap.

Failing that it could be the master relay?

[hotwire 352]

Sounds like time to get it professionally checked as you are prolly just plucking staws with this

[justin_cosgrove 4]

Thanks for the replies guys. I haven't had time to check the relays or anything else but I have noticed my new battery was shorting on the bonnet (thankfully no real damage). I sorted that and have been driving it today and it seems fine. Could that have been causing that kind of trouble with the car? I'm not a noob with car electronics, having modified/ changed wiring harnesses, engine types and modified ECUs in my mitsis. I am however new to the ways of the Bimmer and thier tipical german behavior

[_Matt_ 42]

Same principals haha

[Vagicle 1]

Hey are you still having this problem?

This does not sound like a relay to me. This sounds like either an earthing fault, or a battery fault. I would do two quick checks to narrow this down a bit, mostly just because auto-electricians are freekin' expensive, but also because this could be a quick-fix.

1. Check the negative connection both at the battery and at the earthing stud on the chassis. If your battery is in the front this should just be a really short bit of cable [say 6 inches] from the -ve terminal of the battery to the earth stud, located near the right hand suspension mount. At the battery terminal, even if the connection feels secure, if there is some serious corrosion going on it will still destroy your connection. So if it looks like your battery has been snorting more white stuff than Whitney Houston [too soon?] I'd take the clamp off and clean up both the battery terminal and the clamp itself. Rough it up with some sandpaper or scour it with a screwdriver.

At the stud there should be a locking washer to help get a good connection. If not they cost like $0.50 at the Bolt Shop. Also rough up the surfaces to ensure a good connection.

While your at it put your multimeter on DC and test from the stud to the positive terminal just to confirm you have +12v. Whilst testing give the negative cable a vigorous wiggle and see if the voltage cuts out. Its unlikely but worth a try.

2. Take the battery out of the car and put it on a flat surface. Test to confirm you have +12v. Get some one to tilt the battery to either side while you continue to test for voltage. Do it both slowly and quickly to mimic turning in your car. If at any stage the voltage either drops below 12v or cuts out all together - you have your problem.

I know both of these are basic tests, but you'd be surprised at how often the fault is something really simple. Hope this helps.

[andrewm 236]

My e39 was dieing occasionally when i coasted, everything was tight and fine but I took the battery out sanded the terminals even though they were mint, vaselined them them put it on my charger which only took 4 hours to top off and reinstalled tightly. No problems since, before that I checked alternator and every ground and nothing.

[Neal 544]

Thanks for the replies guys. I haven't had time to check the relays or anything else but I have noticed my new battery was shorting on the bonnet (thankfully no real damage). I sorted that and have been driving it today and it seems fine. Could that have been causing that kind of trouble with the car? I'm not a noob with car electronics, having modified/ changed wiring harnesses, engine types and modified ECUs in my mitsis. I am however new to the ways of the Bimmer and thier tipical german behavior

Sounds exactly like the problem. Most battery's around 600 cca + are close to bonnet in terms of terminals due to size. Had a similar problem on my e30 when fitting the largest battery possible (680 cca)to run the stereo / car (before optima batteries where around). Best you can do is get a battery terminal cover for the plus side and duck tape the inside of bonnet above the plus terminal. If it was shorting out the ecu and onboard diagas. will go mental going between 13.8 volts and 0.

Also make sure that the battery is strapped / clamped down properly so the battery isn't moving around.