Alternator question - PeachParts Mercedes-Benz Forum

Blair Mahaffey · #1 10-04-2007, 02:04 PM

Hello Everyone,

Long time, no post...

I need some assistance with my alternator. I am replacing the original. I purchased a rebuild, but the pulley on the rebuild is single.

What is the best way to remove the double pulley from the old? And what is the best way to torque the double pulley on the new without any damage?

Thanks,

vstech · #2 10-04-2007, 02:09 PM

impact wrench.

toomany MBZ · #3 10-04-2007, 02:55 PM

Quote:

Originally Posted by vstech

impact wrench.

Yep, the place I bought mine from, did it for me. Didn't know at the time my brother-in-law has an electric one. There is a woodruf key also, don't lose.

sailor15015 · #4 10-04-2007, 03:42 PM

Put the pulley in a bench vise while you loosen the nut. I got the alternator off my 65 amp unit and my new 115 amp unit this way with no problems.

Blair Mahaffey · #5 10-04-2007, 03:50 PM

Thanks for the information.

Can someone elaborate on the woodruff key? What does it do and what do I need to know about it?

E320wagon'94 · #6 10-04-2007, 04:01 PM

I know when I replaced the alternator on my 240D (not sure if its the same for the model you may be working on) but the shaft on the alternator had a allen headed insert build into it.

barry123400 · #7 10-04-2007, 04:27 PM

The woodruff key keys the pulley to the shaft so it does not turn around in relation to the pulley bore under load. There is a small area cut out of the shaft and pulley for it to fit in called a keyway.
The impact tool to pull the pulley retainer and attach them is by far the best tool. No chance of pulley damage then. Plus you get reasonable tightness when putting the pulley back on.
This is one thing a garage may do free as it only takes a minute and is so easy with an impact tool. Not too much free left out there...I just enjoy being charged for use of an air chuck to put air in my tires on occasion.

chetwesley · #8 10-04-2007, 04:28 PM

The woodruff key is a not-quite-half-a-circle key that fits into a little slot on the shaft of the alternator. It fits into a groove on the pulley so that the pulley stays in place when rotating.

When you loosen the single pulley and put on the double, just make sure you don't lose it, as it is just fit into the groove and held on by the tension of the nut and will fall out when the pulley comes loose.

It must not be a 240D because I think they only have a single pulley.

I had a similar problem a while back -- needed to put a replacement double pulley on an alternator. I took mine to a local alternator/starter rebuild shop and paid them $5 to take off the old one and put on the new one because I don't have an impact wrench. A lot of car parts stores like NAPA won't do it for you though, because they don't want to be liable. The local guys are cool and know what's up.

Ken300D · #9 10-05-2007, 09:42 AM

I was able to change mine out by just using a large screwdriver to hold the cooling fins. Didn't require enough force to bend them.

The rebuilt I bought for the 300SD seemed to be reasonably good quality, but it came with the single pulley. It turns out it was also missing the woodruff key and a washer. I got those parts switched over from the old alternator and the rebuild has been fine. I had to go with a rebuild because the bearings finally failed. It was a EBay deal and the price was half that of WorldPac. Other than the pulley issue, it seems to be a quality rebuild.

Ken300D