Calling all BMW wizards

pjv911 · pjv911's Garage

I have a 1995 325ic that has a strange problem. Since buying the car 1 year ago the car has had a problem I cant seem to trace.

Basically whats happening is my alternator has a loud pulsing whine regardless of engine rpm or battery charge state. Also doest matter if the electrical system is loaded or unloaded.
Along with the whine is fluctuating light bulb brightness in tune with the whine. The speed of the fluctuation is very rapid. Its apox 200 times per minute. Also its not uniform. It changes speed constantly regardless or engine rpm. Also it never gets faster in relation to engine rpm. It happens whether the engine is hot or cold.
About 6 months ago the alternator took a crap and was replaced with a rebuilt unit. The alternator swap had no affect on this issue.
As for electrical system alterations the only thing done was the install of a stereo amp which was done by the previous owner. It is however wired correctly and shuts off with the head unit. The symptoms happen with the stereo off as well.
Hopefully this is a common issue and somebody will step up with something for me to check. From what I found on a google search it seems these cars have a lighting module and this may be the culprit. However I don't know what or where that is. Nor do I prefer changing undiagnosed parts.
Any help would be greatly appreciated at this point.
Thanks,

Kurt Williams

LiquidBMW76 · 02-18-2007, 12:38 AM

Sounds like a short or loose wire coming off the alternator.

jdob28 · 02-19-2007, 10:21 PM

Sounds like a voltage regulator but if you changed the alternator, you changed the voltage regulator too. I've seen batteries do strange things. Try temp installing a known good battery. Also, check and see if the voltage is changing in time with the whine. If the voltage is changing and the battery is good, then something else is momentarily loading up the electrical system. Not sure what it would be though. I hate electrical issues like that. Very hard to pinpoint. Good Luck

BMWCowboy · 02-20-2007, 03:56 PM

Your Alt pulley is bad~~>very common & you need to replace that & the tensioner

pjv911 · pjv911's Garage

Quote:

Originally posted by BMWCowboy
Your Alt pulley is bad~~>very common & you need to replace that & the tensioner

Is there a way to cornfirm the pulley is bad. What should I look for ? Is it slipping on the shaft ? Same for the tensioner. I apprieciate your input. Thank you.

Kurt Williams

BMWCowboy · 02-21-2007, 05:03 PM

What haPpens is dirt gets in from the back side~~>U can take the belt off & spin it by hand

pjv911 · pjv911's Garage

Quote:

Originally posted by BMWCowboy
What haPpens is dirt gets in from the back side~~>U can take the belt off & spin it by hand

?

BMWCowboy · 02-22-2007, 06:39 AM

u cant read??~~>take off the belt & start up car & see if noise goes away

Jeron · Jeron's Garage

Quote:

Originally posted by pjv911
Is there a way to cornfirm the pulley is bad. What should I look for ? Is it slipping on the shaft ? Same for the tensioner. I apprieciate your input. Thank you.

Kurt Williams

BMWCowboy isn't saying the alt itself is bad he's saying the test bearing of the tensioner pulley on the alt belt and to replace the alt tensioner itself as well.

You should be able to test the pulley bearing by spinning it by hand. Pull the AC belt and spin that one to see if they differ. There is also a deflector pulley on the alt belt.

Check prices but you will probably want to order these though Pelican the dealer and autopart stores were expensive.