I think I may have a similar problem on the 1998 I just bought.
Have receipts from him for new alternator install, but no details on make or brand. Was a small garage, handwritten receipt.
Previous owner said he'd been going through batteries as of late and kept getting them replaced at Walmart for free. Also stated that since the alternator replacement the dash lights don't dim very much with the dimmer control and I confirmed this is truly the case.
Checked the battery with car off and it reads 16V... yes, folks, I think we have a problem.

 

You should test for ohms with different settings/lead inputs than for volts.
Check out this pictorial ... might help. At least I think that's what you're asking.

http://www.wikihow.com/Use-an-Ohmmeter

 

Legender that sounds like a heck of a problem, mine with the car off would fall into the appropriate range but only overcharge when on. Yours is high even with the car off that seems really weird.

Wish I could be of help to ya. Maybe one day..