Hi, I have a 1989 740 GLE, with the BF 234F 16valve engine.

A month or so ago I made a short trip to the store. Car started fine. When I came out less than 5 minutes later, the car wouldn't start. I checked the battery connections, and they were tight, and I use dielectric grease to prevent corrosion.

After 15 minutes of pondering solutions, I tried it again, and it started up weakly. I figured I hadn't driven the car enough the past couple of weeks and the battery was weak. I drove it around to charge for about 30 minutes. Seemed to solve the problem.

Has been starting fine in the mornings, but whenever I try to restart the car, less than 10-15 minutes after driving, it will not. Waiting seems to cure the problem. I checked the +/- connections with a multimeter, and I was only getting about 12V with the engine running. From what I've read, the alternator should be giving me about 13-14 at 2000rpm. I began to suspect a weak alternator.

Finally last week there didn't seem to be enough charge in the battery to start, so I jumped it with a portable jump starter, and it was fine. Later that day I replaced the battery. After installation, the car started weakly, and I had to wait 15 minutes after driving it half and hour to restart. Now I'm pretty sure of a weak alternator.

Has anyone had trouble like this? I believe the alternator is stock, or atleast a Volvo/Bosch branded alternator of indeterminate age. I've read about replacing the brushes and diode, but was wondering what type of shops rebuild alternators and if a rebuild is advisable over a total replacement (new or rebuilt). PS. I've recently moved to the coast, so I was wondering if the salt air could be corroding things like the grounding wires on the alternator or coming off the + terminal at the battery.