Hi forum, I am in need of some advise and expertise.
My wifes 94 940 Volvo died and the cause seemed to be the alternator!

It is a high mileage car (+270.000) and we were looking for an affordable fix.
I got the alternator and went to Autozone to have it tested!
The old NipponDenso 100A is dead and I got a compatible 80A model from Autozone.
Remanufactured and cheap...

Put it in, nothing... turns out the battery (from 2003) also died with it.
Got a new battery and - yay - car started and drove.. for two days (~30miles)
Turns out the battery was drained again!

I am not a mechanic and need some help here.
Here is what I have done:
Jump started the car, metered the voltage after removing the starter-cable
- Voltage drops slowly and constantly!
Disconnected the battery while car was running, car died immediately!
Measured resistance between PLUS at battery and NEGATIVE at alternator:
- starts out at 800Ohms, then climbs up until the meter cannot measure it anymore.
WHY does it read anything at all?!? Normal? Bad alternator? Bad wiring?

I am pretty sure I built in the new Alternator the right way.
However there is one tiny cable that puzzles me.
The Old alternator had ground, positive and a small red cable connected to it.
I have connected this tiny cable to my new alternator, but had to disconnect some extra device on its back for it! (some Bosch component).

What are the odds the reman. Autozone alt. is dead too?! Is there anything else going on?!?

 

OK, returned from Autozone.
Their alternator tested out fine - twice.

Argh! I have no REAL clue how to go from here.
Any guesses?!

 

I believe disconnecting the battery whilst its running can cost you $600 in computers, don't do dat.!

I'm having trouble following your proceedure, I do it very simply like this.

Engine stopped, read voltage at battery. 12+v
Engine running, read voltage at battery. 14 + - , not higher than 15v.
Engine running, read voltage at rear of alternator. Should be very close to battery reading.

Does your alternator have internal or external regulator?

If the regulator goes south it will go full open and generate too much voltage, 20V+

that will kill the battery.

 

oops, to be honest that was some "advise" I got from another guy - will NOT happen again.

Battery reads 12V when Engine is stopped
Engine running: Voltage dropped continuosly and will even go under 12V
I will have to test the rest tomorrow or on Sunday!

The regulator on the alternator is integrated (Bosch) - the kind that has the brushes attached.

 

I'd say your brushes are worn out , no wait, you installed a new alternator?
Brushes need to seat and deglaze but I think you still have a wire issue.
The small wire ( I think it comes from the charge light on the instrument panel) provides exciter current to the alternator coils, that allows it to generate voltage. There might be a fuse link close by too.

http://www.brickboard.com/FAQ/700-90...torNotCharging