Trouble starting and battery light on in dash - BMW Forum

dzuvia9 · 08-10-2011, 12:47 PM

1990 525i

I just had a new head unit installed and I was curious if that could be causing the batter/electrical problems.

Whenever I do eventually get the car to start, the radio will turn on and when I put anymore of a load on the system, like lowering the windows, or lights, or defrost, the head unit will turn off and it seems like the car is going to give out.

The lights seemed extremely dim the other night and even the check battery light seemed to fade in and out with my decelerations and accelerations.

Before the new head unit, the battery did have problems going flat occasionally, put it almost always started and never had electrical problems.

Alternator? Voltage regulator?

Jack Dabsy · 08-10-2011, 02:00 PM

Like you said, alternator ! Or maybe a mickey-mouse ground/earth issue !!

dzuvia9 · 08-12-2011, 10:49 AM

Well, I had both the alternator and the battery checked. They are both good.

So, Dabsy, our only other option is a mickey-mouse ground/earth issue!!!

Or, maybe a voltage regulator? Not sure, leaning toward mickey-mouse.

Jack Dabsy · 08-12-2011, 01:58 PM

Generally speaking, the alternator deals with "regulation" ...
I would firstly, check the head-unit installation and work back from there (Cautiously avoiding Minnie Mouse)!
Maybe put an ammeter on the battery and test it with and without the key in (on acc)...
HTH

dzuvia9 · 08-12-2011, 05:48 PM

The HU install was a complete re wire. My BMW did not have the option for a harness install for the radio. We decided to completely avoid the common ground setup (and Goofy while we were at it) and just wired all the speakers to the HU directly. The guy even took out the old factory amp.

All the connections were soldered and were well done.

Looks like I am going to have to go diggin'

njtl001 · 08-13-2011, 04:30 AM

Quote:

Originally Posted by Dabsy

Generally speaking, the alternator deals with "regulation" ...
I would firstly, check the head-unit installation and work back from there (Cautiously avoiding Minnie Mouse)!
Maybe put an ammeter on the battery and test it with and without the key in (on acc)...
HTH

You are so interesting,

Jack Dabsy · 08-13-2011, 06:53 AM

Thank you !!

dzuvia9 · 08-19-2011, 04:50 PM

So I put in the new voltage regulator, the car only seems to be running worse. The radio starts to short out more and the car itself seems like it is giving out, only to suddenly jerk back.

Jack Dabsy · 08-20-2011, 11:02 AM

Deffo a BAD connection mate... Looking like it's throwing the new reg out too !!