‘95 M3 wiring issues

[mattricharde36]

Hi guys so last weekend I was on track I started to have a weird electrical problem. The check engine light and the ABS light came on so I pulled into the paddock to recycle the ignition and the car wouldn’t start as if the battery was dead. After jumping the car multiple times and it not getting enough voltage to stay running I decided to get a new battery. I had replaced the alternator about a month ago so I know that works fine. I had the same issue the next day with a new battery. After I got home I was unloading the car and as I went to roll it off my trailer I unlocked the steering and tried to fire it up. The car fired with ease like nothing was wrong. It’s not stuck in the driveway with the same problem. I’m guessing it’s a bad ground somewhere but I’m unsure of where all the grounds are for the main circuit the battery is on. I cleaned the battery leads, ground strap, and the engine ground strap so far with no luck.

[shogun]

Moved to E36 M3 forum

[nick325xit 5spd]

First and foremost, do NOT assume that a new alternator is good. Unfortunately, the default assumption should be that a new alternator is bad. That's how poor the quality is. Yes, even the Bosches.

After that, you should check the ground straps and the main power leads, but I'd lean towards bad alternator.

Edit: I was just stranded by an 18 month old Bosch alternator. In a car that's been driven maybe 4,000 miles in that time, for example.

[toussi1]

Get electrical grease, and go over every sensor/connection/joint you can think of. That's what I plan on doing, these metal connections get corroded after some time. You can do the same with the fuse box.

[Smknkeyz]

I'd check the leads on the battery again to make sure they're tight. I went through a similar thing and it was a loose/faulty negative connection on the battery that was intermittent.