Any Alternator experts out there? - PeachParts Mercedes-Benz Forum

jerryb1 · #1 08-06-2008, 12:41 AM

90 300 SE.
Can some one tell me what the field winding resistance should be on this Bosch regulator? I had an intermittant charging problem described on another post. I took a regulator from a 91 300SE and put it in with the battery disconnected(neg terminal) When I hooked up the terminal it sparked and blew out the regulator. Car off. Since the regulator only has three terminals, ground and the two brushes, I can't imagine why this happened. I thought maybe the field windings are shorted. The two regulators appeared to be the same. The 91 had a cap or resistor accross the top. Replacement parts call out for the same regulator for both MY's Unless maybe one of the alternators were changed by previous owners and the two brushes are reversed. This is mind boggling to me.
Thanks for any help!

teezer · #2 08-06-2008, 10:27 AM

you're going to have to pull the alternator off to check the windings ~~~ now that it's off, i'd stick the old regulator in and have it tested at a shop

jerryb1 · #3 08-06-2008, 10:43 AM

Thanks- Is removing the alternator straight forward? Any tricks I should know? The Maintenace CD i have skips over how to remove it. I will get it rebuilt if necessary, but since I have two, i'm sure one or both is good. I also know at least one regulator is bad. if I have the right information, I know I can determine what's bad.

Michael Pillay · #4 08-07-2008, 08:26 AM

Taking the alternator of is not difficult. If you get under the car you will see the 2 bolts holding it in place. The top bolt might give you some problems. Other than that, once the belt is removed the alternator can be out in a few minutes.

jerryb1 · #5 08-07-2008, 09:44 AM

Thanks Michael,
I was concerned I had to loosen the belt tensioner.