not the alternator? - BMW Forum

markp · 01-04-2007, 02:04 PM

hey all! new to the forums! need a bit of help here...

i own a 93 318is and its been having lots of problems recently. the check engine light went on and while driving it gets really sluggish (especially uphill). the clock/mileage/temp all dims... and by the end of driving it 5 or so miles... this morning, the windows wouldnt roll back up...

i thought it was the alternator.. but i took it in to get checked, and the folks said it was fine who tested it.

any ideas what else it could be?

SpeedInfusion · 01-05-2007, 12:45 PM

Quote:

Originally Posted by markp

hey all! new to the forums! need a bit of help here...

i own a 93 318is and its been having lots of problems recently. the check engine light went on and while driving it gets really sluggish (especially uphill). the clock/mileage/temp all dims... and by the end of driving it 5 or so miles... this morning, the windows wouldnt roll back up...

i thought it was the alternator.. but i took it in to get checked, and the folks said it was fine who tested it.

any ideas what else it could be?

voltage regulator?

sounds like u might also have some screwed up wiring somewhere

drz · 01-05-2007, 01:36 PM

Sounds like its a failing voltage regulator. The voltage regulator is integrated into the alternator. The alternator will look good on a bench test because the regulator's failure will not affect performance until after warming up (this is generally how things go). That is why you notice th problem about five minutes after starting the car.

If you don't already have a rather new alternator in your car, I recommend that you change out the whole thing. It will fix your problem. Plus, if the voltage regulator is dead, the rest of the ;aternator is probably on its way out anyway.

markp · 01-05-2007, 06:30 PM

Quote:

Originally Posted by drz

Sounds like its a failing voltage regulator. The voltage regulator is integrated into the alternator. The alternator will look good on a bench test because the regulator's failure will not affect performance until after warming up (this is generally how things go). That is why you notice th problem about five minutes after starting the car.

If you don't already have a rather new alternator in your car, I recommend that you change out the whole thing. It will fix your problem. Plus, if the voltage regulator is dead, the rest of the ;aternator is probably on its way out anyway.

alright thanks guys!

i just went to take it to a 2nd place to see what the results would be... and they said the alternator put out a max of 120amps and said it was pretty good. nothing they could do to improve it...

i drove the car around today and about 5 miles into the drive... it started acting up again... first the gear with the exclamation point would turn on... then the check engine light... then the car would act sluggish like there isnt enough power...

wiring seems faulty possibly?

markp · 01-05-2007, 06:49 PM

oh and this might be a N00b type question...

but on average.. what types of repairs end up costing more?

fixing electrical or fixing mechanical?

im a college kid on a budget here... =P

markp · 01-09-2007, 11:24 PM

i took it into an alternator rebuilding place... they took it apart and said they saw nothing wrong. put it together and bench tested it... it was fine.

is this problem even fixable?

drz · 01-10-2007, 01:01 AM

I had teh same problem -- slapped in a new alternator, and the problem went away. If the alternator people said it looks fine, however, then maybe you should look at your wiring

SpeedInfusion · 01-10-2007, 01:31 AM

could be a bad ground, srsly

agtur2001 · 01-10-2007, 03:06 PM

Hi... I had a very similar issue with my 1993 318is. Swapped out the Alternator/Voltage regulator and installed a new Interstate battery... problem resolved.

However you might want to run a self diagnostic on your 318 and see if the computer tells you anything.

Gator · 01-11-2007, 08:07 AM

Whenever dealing with this type of electrical problem ALWAYS replace the battery or temporarily swap with a known good one and check the battery connections before spending time and money on other diagnostic tests. More often than not it's the battery. In this case an internal battery short or a bad connection could cause the low voltage condition even though the alternator and regulator are good.

markp · 01-12-2007, 12:12 AM

yeah, i replaced the battery with a brand new one.

took the alternator to two places they said it was good... but i dont know... does the bench test show a bad voltage regulator? they say it does... but i dont know if they know anything about bmws or what..

it could be a faulty ground... thats another thing, but from what i see.. it looks fine.

drz · 01-12-2007, 02:48 AM

From what I know, and what other car savvy people have told me, the bech test WILL NOT detect a faulty voltage regulator.

Like I said, I had teh exact same symptoms as you. I would go and have the battery checked and charged at an auto parts store, then I would put it in the car, drive it for like 10 - 15 minutes (from a full charge, remmeber), and then have to head back home becaseu my lights were getting dime, and all kinds of crap were lighting up on my instrument cluster (systems were being starved for power, which trigegred the lights).

I had my alternator bench tested and it passed (twice, I believe).

Somebody told me about the voltage regulator sometimes failing only after it got warm, and that many times you will not be able to detect it on the bench test. Since the laternator is an easy DIY and only about $200 for a rebuilt one, I went ahead with a new alternator and haven't had any problems at all. I mus point out that I was ready to stmach the $200 expense if that didnt work, and then take the car to the dealership. However, it was not necessary.

Before doing this, since you dont seem to want to got this route, first check to see if you are draining the battery some other way. Get a digital multimeter and check to see if you are drawing more current than yoiu should (be sure to charge the battery first).