65A alternator on 1981 cars - PeachParts Mercedes-Benz Forum

JHZR2 · #1 09-09-2010, 10:12 AM

Hello,

Though there is lots of info on here about alternators, one thing I have noted looking at parts catalogs is that for 81 cars, only 55A alternators are offered. On 82 cars, both 55 and 65A alternators are offered.

Curious if there is a fundamental difference from 81 to 82 (e.g. gauge of wires comeing from the alternator) that keeps them from offering 65A versions on the 81 cars. E.g. a liability thing or similar. The parts numbers are the same...

Gillig · #2 09-09-2010, 10:45 AM

Run new wires and use a Saab 80 or 120 amp alternator.

compu_85 · #3 09-09-2010, 11:04 AM

2x. I wouldn't go through the bother to install a wimpy 65a alternator.

-J

vstech · #4 09-09-2010, 11:51 AM

but to answer your question...
yes, in 82 the Turbo was added to most models, so there is at a minimum a tach addition. I think the climate control changed that year also. monovalve, etc.

layback40 · #5 09-09-2010, 09:49 PM

probably the change from 55 to 65 was only a change to the reg. You can get much more than 65 amps out of them if you put 12v across the rotor with no reg, the output voltage is very high & they dont last long though & I dont suggest you try it in a car. You can build a welder from an old alt.

Gillig · #6 09-10-2010, 07:16 AM

Amperage capacity has to do with the number windings in the rotor and stator.

layback40 · #7 09-10-2010, 07:22 AM

It also is controlled by the voltage across the rotor. If you put a 65amp reg on a 55amp alt you will get 65 amps from it. I have done that, If you put 12 volts across the rotor, depending on the load, you will get much more, The flux saturation of the frame will have a bigger effect on the voltage & current.

JHZR2 · #8 09-10-2010, 08:20 AM

I believe the way the regulators are rated, they are or a family of alternators, like 55-115A

layback40 · #9 09-10-2010, 08:31 AM

JHZ,
I believe you are right !!
The reg dictates the output

funola · #10 09-10-2010, 09:03 AM

Quote:

Originally Posted by Gillig

Run new wires and use a Saab 80 or 120 amp alternator.

How much work is it to adapt a Saab alternator to my 83? Does it have the same 3 terminal connector? Does the mounting have to be customized? Last week my alternator stopped charging. I replaced the regulator and cleaned the terminals and got it charging again but in the process one of the screws on the regulator broke (the one that's an electrical connection). It is charging now but I don't trust it without a screw to make a good connection so I am in the market for another alternator.

vstech · #11 09-10-2010, 11:38 AM

Steve, the saab alt bolts directly in but it's much larger physically than the original. and you have to swap the pulley over.
the wiring is different, as no spade terminal can handle 120A
LOTS of wiring posts here
search for "al129" enjoy!

Gillig · #12 09-11-2010, 06:07 PM

Yes, the wiring must be upgraded to handle the current.
You may also need to reclock the rear half if you still have the A/C lines installed. Otherwise the power terminals will be close to the tube.

As noted, the pulley diameter is different to reduce the alternator maximum rpm for the high revving gasser. It won't hurt to leave it as-is, it just means you won't get the optimal charging potential at idle.

JHZR2 · #13 09-11-2010, 10:59 PM

I wonder if the pulley diameter is an issue with my car. Just swapped in a beru 14.2V regulator, and it was only putting out 13.7-8V at idle. I wonder if the wrong pulley was used and so it is not spinning fast enough?