Alternator bad?

[Panici]

Turned my car off today after a drive and it wouldn't start back up. When I checked, battery voltage was @ 10.8v.

Drove it around with a booster pack hooked up, and voltmeter on my dash.
Started at 11.8v, and after driving for 15 minutes it was down to 11.3v

So it's obvious alternator is not charging.

Battery is on a charger right now.



Here's what I'm going to try tomorrow morning

"Inspect the exciter circuit on the alternator. D+ (small blue wire) should have battery voltage when the engine is off and ignition in run. Also confirm that with the key on run and the motor off that your alternator (small battery symbol) light is on. It should go off after the car is started."

and this...

"A shorted primary power connection could cause failure of the alternator. But a bad alternator/battery warning light bulb will prevent the alternator from charging as that bulb is the source of exciter power. A simple check of the exciter circuit is to ground the exciter (small) wire at the alternator. Then turn the key to ignition on. If the bulb lights the exciter circuit is good and the problem is in the alternator. If the bulb doesn't light there is a problem with the bulb, cluster, or wiring."

I'm also going to check the motor ground straps tomorrow.

Anything else I should try before I pull the alt out to get tested?


Also,
Will the alternator from my parts car, '86 325e (06/09/85) fit on my '87 325is (19/12/86)?
RealOEM gives me different part numbers for each car, so I'm betting no. Thought I'd ask.

[lcoleman]

That is most likely the alt, checking the bulb will basically confirm.

The difference is that the early alternators have a rubber bushing and ground strap, while the later units are solid-mounted. I think you're pretty close to the cutoff, and they're probably different. I think you can convert the bracke/tensioner and run an early alt on a late model and vice versa.

[Panici]

That is most likely the alt, checking the bulb will basically confirm.

The difference is that the early alternators have a rubber bushing and ground strap, while the later units are solid-mounted. I think you're pretty close to the cutoff, and they're probably different. I think you can convert the bracke/tensioner and run an early alt on a late model and vice versa.

Ah, so I may be able to pull the mount with the alt, and swap it over?