Retrofitted the N54 180a alternator to replace my 170a N55 alternator

[e80two]

I called it "retrofitting" b/c I technically used a previous gen part not designed for this application. Posting this here b/c when I was searching the forums (here and other places) and the interwebs for compatibility info, I couldn't find an answer. I saw the question asked more than once, never answered though. It would appear that whatever voltage regulator built into the N55 alternator I had finally went out. I was getting a bunch of sporadic errors, such as battery not charging (once), fuel pump errors, then misfires, then the car stopping at random intervals, then sporadic BSD errors, etc. The digital dash and the Android head unit would restart randomly under load, as well. After chasing this problem over 2 months based on the error codes I was receiving, everything finally came down to the alternator. Turns out voltage under load was spiking to over 18v, which subsequently took out the EKPM3, several coil packs, spark plugs due to arcing, etc. In reading some of the stories about when this has happened to others, I apparently got off lucky.

Anyway, when I was shopping for a new alternator, the price for an OEM N55 170A was through the roof ($766 on BMWPartsDeal)! That and they're all reman'ed at this point. The N54 alternator is significantly cheaper, and it has a replaceable Bosch regulator that costs $40, which, in reading the forums, usually negates having to replace the entire alternator. I picked up a BavAuto 180a alternator with a lifetime warranty from Pelican for $268 shipped (kicking myself b/c they were $200 shipped a few weeks ago), and I installed it last Friday. Drops in w/out any modification. The power wire angle needs to be adjusted a bit, and I hooked up the BSD connector, as well. No CELs, I just get a code in ProTool and MHD that it's not the right alternator, but that it. 300 miles in, and everything is running just fine.