Hi, I have a '95 850 Wagon.

OK, here's my problem. About a month and a half ago, my car wouldn't start. I had access to another car for several weeks, so I left it with a VERY well qualified mechanic, and he worked on a number of other minor issues, checked the alternator (it tested fine) and replaced the battery. I went back, picked up the car, drove it back here (it was 200 miles away) and drove it fine for a week.

One morning a week later it wouldn't start. Jumped fine, drove it to work, wouldn't start, jumped fine, etc. I brought it to my mechanic up here 2 days later, he couldn't find anything wrong with it, it started fine for him, he checked the battery, checked the alternator, checked the belts, etc., everything appears fine. No draw from the alternator.

Car starts fine the next two days. Then last Saturday morning, same thing, no start, jumps immediately. If I stop the car after about twenty minutes, I can start it back up for about another hour and a half before it loses power and needs another jump. It's been like that for a week now.

I spoke with the guy who replaced the battery, and I explained the whole situation to him, and his advice is to change the alternator and test that. He is actually willing to do it himself, get the alternator, and if it doesn't work, put back in the old one and not charge me. Only issue for me is I would have to get back down to where he is and leave it with him for a few days, which I can't do for 2 weeks, and I can't go on like this - people are getting tired of jumping me! I called my mechanic here and asked him to change the alternator and he refused, he's so confident it isn't the alternator. He says I should take it to the dealer here, but I really want to avoid paying dealer prices.

Anyone, please, ANYONE have any ideas as to what this might be?

Get to an auto parts store and buy a multimeter for less than $20. That way you can check the alternator output yourself, it should be between 14 and 15 volts. The battery should be 12V.
Then check the draw down on the battery, it should be around .03V Anything greater, you start by pulling 1 fuse at a time to isolate the draw. Time consuming, I know, but this is the only way to isolate the problem.

Klaus
--
1975 164 w/174,800mi (Sold) 1995 850T w/91,000mi, 1998 V70R w/129,000mi

I will try that, thanks!

Well, after doing this with no results and talking with the mechanic who worked on this originally, the conclusion is that the alternator has an internal draw. It's simply losing power too quickly for it to be anything but the alternator (lost power in 15 minutes after idling the car for 45 today). What a pain.

Thanks for your advice!

I just went through the exact same issue on my 97 850 and this site helped me - here's the breakdown on Klaus' advice.

a) Buy a multimeter
b) Disconnect negative battery terminal
c) Measure amp draw between the connector and terminal
d) Disconnect the main alternator wire from the unit itself
e) Measure amp draw again.

If the reading is lower, the problem is inside the alternator. If it stays the same, follow a similar process on the starter. Good luck.

What turned out to be the problem with yours, out of curiosity?

I assumed it was the voltage regulator (from eEuroparts with integrated brushes), and replaced the component rather than the entire alternator. These are the parts commonly replaced when you buy a "rebuilt" unit. However, the problem persisted. Using this advice from fellow Brickboarders (you can search for my posts about one month ago) the problem was determined to be the windings in the alternator itself. Because I had already invested the money in the regulator, I picked up an alternator at a local junkyard for $40 and put the new regulator in it (better than pulling the unit out again next year) and solved the problem for $100.

Is there any light or component that might be drawing current when the car is stopped? An interior light, parking light, an audio device? Or does someone leave the door ajar so that the dome light stays on? Also, are you sure that the battery cables are clean and in excellent condition? Power problems like this are hard to track down, and sometimes it is a real subtle thing.

No, the dome light doesn't stay on, and the cables seem immaculate. there doesn't seem to be anything. I'll have to try Klaus's suggestion.

Thanks for your reply!