alternator test 93' 850ci

[davek43]

How can I test the alternator on the M70? My batteries are 1yr old, but i"m loosing all electric power w/in 1 to 2 hrs. of driving the car. Put the "trickel charger" on, batteries take/hold the charge. Then the car won't start again in less thna 2 hours of driving ??

[justaguyinokc]

Well, the best way is to remove it and take it to a shop or auto store.

Before I did that though, I would check:

1) Serpentine belt and/or tensioners. A majority of the time when I have had charging problems in the past, it was either the belt was slipping or that a connector was anodized or corroded and not flowing current (see #2)
2) Electrical connections from the alternator
3) voltage regulator on alternator.

If those fail to alleviate the issue, then I'd remove it and take it in for testing.

[ladislav]

... pull the voltage regulator off it and check the brushes, esp if it has over 100k mi.

not sure how the e31 idiot light is wired, but on the e32 the idiot light won't go on if either brush is worn out.

however, i don't think this is going to be your problem. if your batteries lose all power within 2 hrs after shutoff, sounds like you have a short somewhere.

not a fun thing to track down. expensive if you have to pay for it and lotsa time pulling fuses and relays if you do it wourself. there is a lot of wire in these babies, has the car ever been hit?

in the meantime you might want to purchase disconnects and keep the batteries floated individually.

[justaguyinokc]

are you losing power WHILE driving?

or, are you losing power AFTER driving?


Big, big, big difference on what the problem is.


During=alternator/charging system

After=batteries, relays, shorts.