I am no expert, but have struggled with related problems. I recommend that you read up on the charging system topics on the 700/900 FAQ page on this site. There is a lot of good information there. Also you can look at howdoesitwork.com and about.com and find more general information about how charging systems work.

It sounds like you may have bad diodes in your regulator (see the sources above). The good news if that's all it is is that a new one is only about $60/$70 and you can pull your regulator without removing any major parts (on my car anyway) but it's tight. Take off the ECU breather tube to allow your hand to get down there.

I only found one place that had or said they could get the exact replacement part (for my 96 850), I think it was called RockAuto or something like that. Never used them so can't recommend them except they did show the part number on their site. Oher sites indicated a different Bosch part number for my car -don't know if you'll encounter that issue with yours....

The regulator, besides containing the brushes (at least in my 96 850 with a Bosch 100A alternator), is supposed to keep your voltage down to around 12.5 to 14.5 - something like that. It is my understanding that if the voltage at the B terminal (one with the nut)and the voltage at the "little wire" terminal is not the same, then this is another indictment of the regulator.

If allowed to stay up at 17/18V it can ruin your battery (and proably some other electrical components), so you might also have a bad battery by now.

To check your cable between the alternator and battery +, check your voltage from the battery + terminal to the frame or block. It should be only about a .2 V difference from that measured at your B terminal (with the nut) on your alternator. If it's much more than that, you have a drain from that cable.

Finally, you can take the car to AutoZone, Advanced Auto, etc. and they will check your charging system for free. Sears charged me $10 to do it even though I had a relatively new Die Hard battery. However, Sears and AutoZone both told me I had a bad alternator and (for various reasons) I don't believe them (YET).

Good luck with this troubleshooting. Hope this helps you out. I know how frustrating it is when nobody responds.

Regards,

Calvin (92 940 198K, 96 850 97K)