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All my neighbors think I'm crazy (that guy with the BMW). I've been noticing lately a richer smell (I think just lately) trying to figure out why my bimmer seems I have two different idles (one nice and smooth, another 'choppier'). Other than this car drives great.

I am getting 13.53 volts from alternator and battery on my 55 amp alternator. My generator dash light glows dim, and dimmer with more accessories on.

With just headlights on, my idle will drop and my car will start to sound rougher. Auxillary fan and its even rougher, etc., you get it. I think lights alone shouldn't do this.

I pulled the regulator (easy job!) and the brushes look good. I cleaned them up. The alternator itself is a year old. Spec is 13.7-14.5 volts and I'm just not there. I imagine if I was, I would have a nicer idle. Clearly I'm getting a weak spark.

Of note is that I upgraded to the 528i transistorized ignition.. would this require me to have the larger 528i 65 amp alternator? Or, is the voltage output in this case purely a function of my voltage regulator? (maybe an adjustable one would work?) I want to be at the top end of 14.5. Also all grounds were checked and cleaned and test good. I'm hoping I can just get away with a regulator swap.

Any points or poetry (T. H!) is always appreciated.

I ordered an adjustable regulator for 15 bucks.
Will post results.

I put a CS130 alternator on my Bavaria - 105 amps and 14.5v all the time. The AC Delco and Bosch are very similar in size and mounting so it's a pretty easy swap, and cheap, too.

I'm a big fan of the Bosch alternators BMW put on their cars. I've never had one fail. A couple of regulators yes, brushes, yes, but no alternators. A different brand or capacity alternator isn't going to make much difference, 55A is really quite a bit and they all do the same thing, convert mechanical energy to electrical energy, all with more or less the same efficiency. To the OP, it sounds from here like a bad ground, check the voltage of the alternator at the alternator, from the positive post to the alt body and see what voltage you get. Then compare that to what you get at the battery, if it's off by more than a quarter of a volt or so you have a wiring problem.

FYI there are only 26 brand new 12311277504 (528i 65amp) alternators left in the world!

JodyStevens wrote:FYI there are only 26 brand new 12311277504 (528i 65amp) alternators left in the world!

As long as they last, and as frugal as most of us old BMW owner are (and yes, I'm including myself) there will probably still be some left at the start of the next century.

You're probably right, they are about $350.

My 105A alternator cost me $22...

OK.

First, I bought a cheap 5 dollar cigarette lighter voltmeter and checked it for accuracy at the battery.

I also bought an inexpensive voltage regulator and I think for the 15 bucks it was worth it.

I upped the voltage a bit and now when I turn on my lights and some stuff it drops down to acceptable levels without making my idle get slightly rougher... unless I turn on a bunch of stuff, then I end up in the same place

The difference is minimal but worth it IMO. but I think a larger alternator (even 65 amp) might be worthwhile but not necessary.

I didn't buy here, but there is some useful info here if anybody is interested in the adjustable regulator:
http://www.davebarton.com/AdjustableVoltage.html


Thanks for all the input!

65 amp bosch premium alternator for the 528i is available from FCPEuro for $121. Damn good price if you ask me:

http://www.fcpeuro.com/products/bmw-alt ... 733i-al41x