740 alternator brush wear

I have an apparent alternator problem with my 87 740 GLE. Per my Haynes manual I removed the regulator/brush assembly and found that the rear brush (closest to regulator) was probably just about at the 5mm spec distance at the low point of its concave and the contact edge was blackened. The other brush was several mm longer with a shiny contact edge. Am I right in assuming the bushes need replacement? Is the uneven brush wear typical? Is there generally good success in replacing just brushes ($3 at FCPGroton) or regulator/brush assembly ($24 at FCPGroton)?

Reply to
Raymond Cruz
Loading thread data ...

best to simply replace the whole regulator assembly. you don't want to chance the problems of possible overheating of the regulator from the too close contact of the brushes.

Reply to
MudPuppy76

Uneven brush wear is not a good sign, make sure you feel the sliprings with your finger to make sure there isn't a nick or crack in one wearing down the brush. I've always replaced the whole regulator but if it's in good shape I suppose it'd be worth trying to replace the brushes, I didn't know it was possible.

Reply to
James Sweet

Also make sure that the brush is not binding in it's holder which tends to cause arc burning of the brush.

Cheers, Peter.

Reply to
Peter K L Milnes

I always replace the whole assembly. Usually I'll Start the car and carefully polish the slips rings with a piece of scotchbright. The brushes always seem to arc more on the rear side than the front. Uneven wear is not unusual.

Bob

Reply to
radietz

Thanks for the tips. I bought the new assembly but I can't figure out the technique for getting it in place. Since the new brushes are quite long it seems it would be best if they could be compressed while sliding the assembly in. I tried placing a screwdriver in the cavity of the alternator such that I could push the unit down onto the screwdriver, compress the brush springs, and then push the assembly in but I think I'm bumping into the conducting clip spring. I also tried tilting and inserting various ways but I just can't get it to seat properly and I'm starting to chip the ends of the brushes. Anyone know the trick?

RC

Raym> I have an apparent alternator problem with my 87 740 GLE. Per my Haynes

Reply to
Jay Tanner

It's tough but you just have to work at it and eventually you'll get the angle right and it'll just slide into place. Don't force it too hard as you can crack the plastic. I've found that on 240's it's virtually impossible to get it in without removing the alternator, but 740's are quite a bit easier.

Reply to
James Sweet

It's been a while, but IIRC I tied thread to the braided wires on the brushes and pulled them back while putting the regulator on, then broke the threads off.

Mike

Reply to
Michael Pardee

Here's how I got the regulator/brush assembly seated. I noticed the original assembly had small holes in the bottom of the outside housing walls and there was a small channel in the housing partition that keeps the two brushes separated. It was evident that the brushes could be pushed all the way into the housing and some straight, fine, stiff wire could hold them in place by passing through the two holes and the channel. Once the assembly was seated the wire could be withdrawn. Unfortunately my replacement part didn't have the holes or channel but I used the same general idea. I drilled a 1/16" hole through the bottom of the wall at the end of the housing that extends deepest into the alternator. Then I unfolded a paper clip and made a small hook in one end that could catch in the hole while the long length of the clip wire was pressed against the bottom of the housing holding the brushes up in the housing. Once the assembly was seated I pushed the wire forward enough for the hook to clear, twisted, and then was able to pull it out.

Neither assembly allowed me to see any of the braided wire so the idea of tying thread to those wires was not possible. As for trying to tilt and slide, I wasn't successful and each time the brushes got a little more nicked. My first impression is that the alternator is OK but I'll need to determine that over the next couple of days.

Thanks to all who offered suggesti> Thanks for the tips. I bought the new assembly but I can't figure out

Reply to
Jay Tanner

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.