Porsche Enthusiasts Club Forum

So as a couple may know I had a charging issues a couple of weeks ago.

I have three alts so assumed I can make a good one. One works but the bearings are complaining so its only a matter of time.

The one which came off, the light on the dash was dim and the voltometer was reading 12-13, so just enough to get by but a good volt short.

So I ordered a pair of bearings, bosch regulator come brush holder, and new slip rings. Fully dismantled nothing stuck me as buggered so i put it through the sandblaster and then parts washer. It all looked pretty good for 30 years old. I then resistance checked the rotor and stator. Less my multimeter resistance all the winding's are within spec. I checked all the diodes they are all unidirectional and half opposite to the other.

With all seeming ok, I removed the bearings and slip rings. Soldered the slip rings and tested, readings remained the same. The earth from the stator to the diode pack broke off at this point so I soldered back together, rechecked resistance and it still read the same spec.

Fully rebuilt the unit and fitted. Much to my joy the alt light came on and stayed on, going to half brightness at 3000rpm.

So what have I missed? bearing in mind a serviceable unit does work on this car so its not a car wiring fault

No one??

I don't know enough about the internals of these to comment really, therefore my advice is to source a known good used part or bite the bullet and buy new. Or send yours off to be rebuilt.

Not really what you want to hear i suspect!

Have known this to happen with a bad connection with the regulator brush holder to alternator held in place with two screws.

If you need another decent altenator I have one cheap

Thanks gents!

I had a check of the brushes and the we contacting. Having sand blasted the body and fitted new brushes I was hoping it wouldn't be that.

I let the anger subside and today I bench tested with a light, and when spinning there was a point when the light when out. And when I spun it with a cordless drill I could hear a clicking noise. After pulling it apart I found where I had soldered the rotor wires to the slip rings Id left a raised edge causing the brush to jump. Just to be sure I put a different rotor in and all was cured. Lesson learnt, be more careful when soldering!

So a trip to the lathe at work tomorrow to make the slip rings concentric again should see me with a lovely next to brand new alternator for under £30