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View Full Version : voltage problems on 1992 325i - help please!

dgoss
11-08-2006, 10:45 AM
Hi all,

I'm having an issue with my 1992 325i that has 95k miles on it.

Perhaps every third or fourth time the car is driven I will get the check engine light in a sort of ocillating manner. I read the code a while back and I believe it was low voltage (it was definitely a voltage code). The car in this "mode" will toggle the AC off if it is on - if the AC is put back on it pops off again. Then usually at some point the tranmission is triggered into safe mode.

I have searched here a bit regarding the safe mode and read a little where a poster had suggested that in practice this is often a voltage/electrical issue that triggers this mode.

Also, when car is not doing any of the above the onboard computer lights or any small instrument lighting has a small pulsing as if the voltage is uneven.

I am going to have the car looked at but wanted advice here first please. This car is not driven a lot (hence I've mananged to get along with the above for the last while) and I am about to sell it once this issue is resolved.

It is very important that I try to keep the cost of this repair as low as reasonable - I'd love to hear if this is often one particular part or if I should be careful about a particular mis-diagnosis that could cost me a lot and not resolve this.

Thank you for any advice in advance -

Best,
d.
bimmer dot info
11-08-2006, 11:04 AM
sounds like a failing voltage regulator. It is Part 13 (http://realoem.com/bmw/showparts.do?model=BF31&mospid=47430&btnr=12_0400&hg=12&fg=22) of the alternator. Test the running system voltage to confirm. Should be a solid 13.8 or so.
Waveho
11-08-2006, 11:04 AM
First most obvious check would be the voltage regulator. I've not had to replace on my BMW, but was a cheap and easy replacement on my old T-Bird. Many newer vehicles have integrated alternator-VRs, but I believe in this vehicle still (I have the same) it is a separate unit. Note that it is often the case that where you have a VR problem, there is a fault in the alternator, and vice versa. Most mechanics will tell you that when you find the need to replace one, you should replace the other....
Waveho
11-08-2006, 11:08 AM
Wow, Bimmerdotinfo, that price for the VR in the provided link seems a little high for a VR, even for a Bimmer. The VR for my T-Bird was about $20; but I guess that comparison isn't really a fair one. Still....
Waveho
11-08-2006, 11:08 AM
Wow, Bimmerdotinfo, that price for the VR in the provided link seems a little high for a VR, even for a Bimmer. The VR for my T-Bird was about $20; but I guess that comparison isn't really a fair one. Still....
dgoss
11-08-2006, 12:33 PM
I'll measure the voltage bimmer_dot_info. Since I'm getting rid of the car maybe there's something to be said about just swapping the voltage regulator instead of the whole alternator assembly.

I seem to have located a bosch regulator online that is around $50. But I'm hearing that this car had two different model alternators, a Bosch and a Valeo?

Ok, so at least this is the likely path. Thanks for the help so far!
Derekj
11-08-2006, 03:53 PM
Before you spend any money on a voltage regulator, I would suggest you look for a bad ground. Check you battery terminals, Where the wires connect to the alternator, run your hand along the wires at the back of the alternator and check if there is not a bit of chafing going on etc.
Good Luck Derek
Bimrpwr
11-08-2006, 05:31 PM
with derekj, Check out your ground wires and power connections going to ALt, Starter and Battery. Are you running any heavy stereo equipment?
dgoss
11-08-2006, 05:39 PM
Are you running any heavy stereo equipment?

no, car is all stock.

Thanks for the tip Derekj and Bimrpwr - I'm stuck getting some work done but I'm going to try and check the connections tomorrow first and read the voltage as well.

Sorry for all the newb questions but I have no experience - is there a particular place to pull the voltage from or just find a source in the fuse box while the car is running?
Bimrpwr
11-08-2006, 05:50 PM
you can pull it from the battery while the car is running. bout the easiest spot unless u have a radio like i do and it tells you the voltage :)
Derekj
11-09-2006, 05:22 PM
Like Bimrpwr says....check at the battery. If the voltage is low then another way is to disconnect the leads at the back of the alternator and test directly at the back of the alternator without the wires connected. This will determine if your alternator/regulator is bad and also if the reading is good then you have a short in the wire going to the battery.
Cheers Derek