I just had my dad's '87 635 out last nite and it died on me. It would crank over and start and then when I put the lights on it died. Earlier that day when starting, the indicators lights stayed on for a few moments and then went off after I got underway. I thought then I may have some kind of problem rearing it's head. I went back to the car today and changed the battery and it fired right up and I drove back home. I swapped out the alternator with one I had in the shop from our '86 735 that we parted out last year and checked the belt and all the connections. Question is: How to I verify the output of the alternator and /or voltage regulator?? I drove the car tonite with the lights on and all seemed well with all dash lights staying out during the drive.