Alternator woes: Failing Voltage Regulator? - PeachParts Mercedes-Benz Forum

haromaster87 · #1 01-31-2013, 10:50 AM

Quote:

Originally Posted by Silber Adler

It might be a loose connection that is noticed because the engine shakes at idle.

Was all over that thought. Even found my positive battery terminal loose and tightened it and thought I had fixed it. Once it started happening again, I inspected all cables and tightened all connections.

Quote:

Originally Posted by toomany MBZ

Go ahead and pull the regulator, inspect the brushes.

Ah, that makes sense. This will actually be my first dealing with a failed regulator so I didn't know you could visually inspect wear on them. If the brushes look okay, is it possible for another component in the regulator to fault out?

Fattyman · #2 01-31-2013, 11:05 AM

Quote:

Originally Posted by haromaster87

Was all over that thought. Even found my positive battery terminal loose and tightened it and thought I had fixed it. Once it started happening again, I inspected all cables and tightened all connections.

Ah, that makes sense. This will actually be my first dealing with a failed regulator so I didn't know you could visually inspect wear on them. If the brushes look okay, is it possible for another component in the regulator to fault out?

Your diodes might be going belly up as well.
Time to throw an regulator in there. It's a 15 minute job and they cost around $40. If that doesn't fix it at least you'll know it's not the regulator!
Fluctuating voltage usually means diodes, Then loose connection, then gremlins, then...............

haromaster87 · #3 01-31-2013, 11:13 AM

Quote:

Originally Posted by Fattyman

Your diodes might be going belly up as well.
Time to throw an regulator in there. It's a 15 minute job and they cost around $40. If that doesn't fix it at least you'll know it's not the regulator!
Fluctuating voltage usually means diodes, Then loose connection, then gremlins, then...............

I like your thinking! Excuse my lack of knowledge, but are diodes internal to the alternator? As in, if it was the diodes, it would require repair or replacement of the alternator?

Also, any word on if that regulator out of the stock Bosch alternator will fit? If so, like I said it's almost new and I can pull it off tonight. I don't think the regulator on the current alternator is actually Bosch branded, so I can't compare part #'s. However, if they are the same shape and size, would the AL129X use a different regulator since it's higher amperage, or would that not matter?

Fattyman · #4 01-31-2013, 11:29 AM

Quote:

Originally Posted by haromaster87

I like your thinking! Excuse my lack of knowledge, but are diodes internal to the alternator? As in, if it was the diodes, it would require repair or replacement of the alternator?

Also, any word on if that regulator out of the stock Bosch alternator will fit? If so, like I said it's almost new and I can pull it off tonight. I don't think the regulator on the current alternator is actually Bosch branded, so I can't compare part #'s. However, if they are the same shape and size, would the AL129X use a different regulator since it's higher amperage, or would that not matter?

Amperage does not matter to the regulator. I think it's a different part number than the 55/65 amp alternators though.
The diodes are internal to the alternator and require you to split the alternator and re solder them on. At that point it's time to just swap it out for a new unit anyway.

haromaster87 · #5 01-31-2013, 02:02 PM

Quote:

Originally Posted by Fattyman

Amperage does not matter to the regulator. I think it's a different part number than the 55/65 amp alternators though.
The diodes are internal to the alternator and require you to split the alternator and re solder them on. At that point it's time to just swap it out for a new unit anyway.

Ah, I gotcha. Would the diodes going out have anything to do with the pegged reading of 14v? When everything was working properly, it would only show 14v at certain running RPM's. Now it was showing 14v at idle and looked like it might've gone a bit above 14v at one point. Does that tilt it more towards regulator or diodes at all?