Additional alternator Q

[M6csi]

I’m considering adding the additional alternator on my 1991 850. Is the instrument cluster 2nd charging idiot bulb socket wired for operation already for the coupes that we’re not equipped (USA) originally?

[shogun]

I have seen it on some M70 in E32, others do not have it, check for this cable http://www.nationalmedia.biz/images/...fyThisWire.jpg

[rogbmw]

I had the second alternator on my first Alpina. To be honest, unless you are stuck in traffic ALOT, it may not be of use to put it in. That was what they were made for, and why many of the Alpina cars sent to Japan had it.

[M6csi]

The current charging system (Bosch rebuilt alternator and 2 Bosch AGM H8 batteries) is undercharging, 13.25-13.50 volts max with engine running. Voltage is not affected by engine rpm, either at idle or high rpm operation. Let’s see if the new BMW oe voltage regulator will resolve this charging issue.

[shogun]

Better replace the cable between B+ and alternator, after replacing the old rotten thing I got 0.5V more than before. After +20 years of continuous service the insulation has failed. While there is some argument that engine fires have been caused by shorts through the cable tube to ground, one problem that cannot be ignored is that the fine cable strands become badly corroded. Corrosion → higher resistance → higher current drop across the cable → higher temperatures → cable fuses. The battery also does not get the full voltage.
http://twrite.org/shogunnew/files/ch...20failure1.jpg

[M6csi]

Installed a new aftermarket B+ cable about 3 years ago.

[CaifanSC]

Bert, are you aware that the pulley on your AC compressor needs to be changed to one that has an extra groove for the Aux Alt belt?

[M6csi]

I did not know this important fact. This really complicates things, probably will end up shelving this project. Thanks for the info!

[CaifanSC]

I did not know this important fact. This really complicates things, probably will end up shelving this project. Thanks for the info!

I don't blame you. I actually have a brand new Aux alternator but have never worked towards getting it installed for that same reason. I don't feel like fiddling with the AC compressor just yet. Maybe when that does need replacement, I'll do the pulley and aux alt. If you ever need the parts just enter a EURO vin # in bmwfans.info and you'll see the part and part #'s.