Please help. Alternator not producing any volts

[chrispurs]

Hi.

I have BMW 520i 93 to 94.
Problems with charging system. The alternator is not charging the battery.
Have had battery checked so replaced alternator still have same problem im stumped.
original alternatator is Valio I have replaced with exactly the same check voltage on battery before starting approx 12.8v obviously voltage drops when cranking but carries on dropping when engine running. Left car stationery with full beam on & heated window for 15 mins voltage dropped to 10.5 im completely baffled can anyone shed some light.
Im sure the charging light on the dash board is not lit to state A problem. Am constantly charging battery every night to ensure I get to work ok.

Thank in advnce Chris.

[AlpineSixAndSeven]

should be the voltage regulator...

[chrispurs]

Hi AlpineSixAndSeven .

Thanks for answering so quickly.
Is the voltage reg after the alternator in the circuit ?
As im certain the voltage on the + wire on alternator & chasis read exactly the same as battery reads when engine is running slowly dropping voltage.
I would expect to see more than 12volts from alternator so are you saying that the voltage reg is inside the alternator & you think this is the problem.
If it is im really p****d purchased this second alternator today from vehicle recycling shop told it was tested & working.

Chris.

[sp0rky]

On your vehicle, the voltage regulator is inside the alternator.
This was my initial thought until you said you had the alternator replaced already. Unless you got a bad replacement alternator...

I would check to make sure that the engine and alternator are properly grounded - and the wiring is in good shape. I really can not think of much else off the top of my head, but if I do think of something else, I will report back.

Hope you get it sorted out quickly

[AlpineSixAndSeven]

Kragens and alot of auto parts stores do free testing
check the gounding strpas(bigish wire(s) going from the block of the motor to the chassis)

[winters97E39]

i emailed my friend who is a mechanic and he said "sounds like he either has a bad drain in the system, or short, or the voltage regulator is faulty. Could be bad in the replacement unit as well. "

He was going to look at a wiring diagram today and see what else it might be. check all your connections, make sure they are tight and correct, and check for any shorts. It is possible the voltage regulator is bad in the replacement alt, so I would go get it checked as well.

[da_bull]

I was thinking make sure your connections at the battery are clean until you said its the same voltage at both the alternator and battery. I would place my bet on the bad replacement alternator too.

[chrispurs]

Hi All.

Thank you for all your answers.
I have now found out what the problem was & thought I would share it so it may help others.
As I said in my post The alternator was made by Valio in the end of alternator where the cooling pipe fits there are 2 carbon brushes that were soldered in these were warn down
& after fittiing new carbon brushes the alternator now works perfectly.
Will be returning the so called recycled working alternator to get my money back.
Thanks again to all who offered help.
Chris....

[winters97E39]

Originally Posted by chrispurs

Hi All.

Thank you for all your answers.
I have now found out what the problem was & thought I would share it so it may help others.
As I said in my post The alternator was made by Valio in the end of alternator where the cooling pipe fits there are 2 carbon brushes that were soldered in these were warn down
& after fittiing new carbon brushes the alternator now works perfectly.
Will be returning the so called recycled working alternator to get my money back.
Thanks again to all who offered help.
Chris....

Good deal! thanks for the update!

[sp0rky]

Just for future reference, the brushes (and the piece that they are attached to) is the voltage regulator. It can be replaced with an entirely new unit for relatively cheap.