Alternator 55 or 65 amp? - PeachParts Mercedes-Benz Forum

JWJ · #1 12-15-2009, 10:12 AM

I acquired a spare alternator for my '83 300D from a yard.

However, the alternator was labeled for a 240D.

The yard says it was mislabeled and is really for a 300D. I can't tell.

The yard alt. and my existing one look almost identical.

A 240D takes a 55amp alt. A 300D takes a 65 amp.

How do you tell the difference in the alternators?

Biodiesel300TD · #2 12-15-2009, 11:41 AM

It's not going to matter which on you use, they will both work. The amp rating for a alternator is the max output that the alternator can handle. A 65 amp alternator will be able to handle a larger electrical load than a 55 amper. A 240 typically has less electrical stuff, i.e. power windows, power sunroof, etc. Therefore a smaller amp alternator works. But if you put in a 65 amp you will just have the ability to pull more amps. If you don't pull those amps you aren't hurting the alternator any. It's just not working as hard.

JWJ · #3 12-15-2009, 11:55 AM

Quote:

Originally Posted by Biodiesel300TD

It's not going to matter which on you use, they will both work. The amp rating for a alternator is the max output that the alternator can handle. A 65 amp alternator will be able to handle a larger electrical load than a 55 amper. A 240 typically has less electrical stuff, i.e. power windows, power sunroof, etc. Therefore a smaller amp alternator works. But if you put in a 65 amp you will just have the ability to pull more amps. If you don't pull those amps you aren't hurting the alternator any. It's just not working as hard.

With what you've written, a 65amp alt. (from a 300D) will work in a 240D.

But, will a 55amp alt. (from a 240D) work in a 300D?

That's my situation, I don't know what this yard alternator is.

Biodiesel300TD · #4 12-15-2009, 12:15 PM

Visually you probably aren't going to be able to tell. Unless there is a part number of some kind. The 65 amp alternator should say AL117X, and the 55 amper should say AL80X.

You might also take it to a shop and they might be able to load the alternator and tell you which is which.

ah-kay · #5 12-15-2009, 12:19 PM

If the form factor is the same then it does not matter it is a 55A or 65A. It only matters if you are using a lot of power 'continuously' when the car is running. It will drain your battery faster with a 55A alternator compare with a 65A. The 55A alterator will replenish the battery charge slower. Unless you are blasting a boom box or running an inverter with a lot of appliances then I would not worry about it.