Hey guys, so I just pulled the engine in my mini and rebuilt it due to a spun rod bearing. Replaced the clutch as well.

My problem now is that for some reason my alternator is not charging my battery. I have two good batteries that have been tested and charged that run the car for an hour or so before the car just runs out of juice.

I wasn't able to test my current alternator, so I swapped it out for one that I had as a spare that I know works fine. The old one felt really rough to turn as if something was wrong with the magnets inside (definitely not bearing problems). Even after that and checking the connections at the starter, battery, engine battery terminal, and alternator I can't get more than a 5V charge out of the alternator.

I suppose it is possible the one I used as a replacement alternator is bad, but is there anything else I should rule out before picking up a new one/rebuilding my current one?

 

Power steering pump is also not working, not sure if that would have anything to do with this though. Was working for a few seconds on first startup after rebuild, but shut off about 15 seconds later and has not turned on even with the engine running since.

 

Check the 50 amp fuse on the back side of the fuse box. If out the ps won't work, and neither will the alt.

Nik

 

Wow, sounds like me last September (and on to a new engine now).

Was the engine out long? Did you charge the battery up before starting the car/getting the car back on the road?

I only ask because the alternator isn't supposed to charge the battery (just maintain the battery under normal usage). Yes it can charge the battery, but it puts a tremendous load on it. Every time I've seen a dead battery, the alternator is close or gone as well and vice versa.

I don't have much to add other than check your engine ground points. After cleaning mine (after the re-install) I was able to get a good voltage.

 

Yeah the batteries were both tested and charged at the parts store so it isn't that. I also checked the grounds, but i'll go clean them and reinstall them to be sure.

I did try to start the car without charging the battery after sitting for a few months so that could've killed the alternator I suppose, butI want to rule everything else out first.

I'll check that fuse.

 

Checked the fuse and cleaned all groung wires, but still not dice. I will probably take the care into the local MINI shop to see if they can find out what the heck it is.

 

You can always take a long screwdriver and carefully touch the pulley while running. if it's working, you will get a magnetic field, allowing the screwdriver to stick to the pulley.
If you put a VOM on the battery with the engine off, it should show approx 12.6 - 12.8 dc volts if good. When the engine is running, you should see a voltage across the terminal of about 13.2 - 13.6 volts.
The brushes on alternators can get really thin and start to work intermittantly, just like your PS pump. The only difference is the battery supports the electrical flow when it happens and you would never realize it until the alternator just plain dies, drawing the batteries down. When it happens in your PS pump, you know it right away when turning.
Most alternators now have the regulator built into the case now and when these go bad, it's time to change the complete unit.