noproblemo2
Member III
TRYING TO FIND OUT IF ANYONE KNOWS WHAT IS CAUSING OUR RPM GAUGE TO BOUNCE AROUND AFTER IT GETS STARTED AND WARMED UP THIS HAS JUST RECENTLY BEGUN.
Alternators should be considered a maintenance item. Alternator brushes and slip rings wear out and must be replaced. On older American alternators I usually replace the brushes at 100,000 miles for a few dollars and get another 100,000 miles out of the alternator. On Bosch alternators the slip rings wear out with the brushes and must be replaced also. This is not an easy DIY project. The least expensive way to have this maintenance done is to remove it and take it to your local auto electrical shop and have it rebuilt. The brushes and regulator on the Bosch alternators are one assembly and must be replaced together, and the slip rings must be replaced also, so it is more expensive to rebuild than other alternators. My local shop charged me $110 for my '88. The frequency for this maintenance is approximately 100,000
miles. I don't know if the amount of air conditioning use affects this figure but if you live in a hot climate maybe you should do it at 80,000 miles.
One of the symptoms of worn brushes and slip rings are "voltage spikes" that destroy the regulator. This sounds OK since the regulator is replaced during the rebuild anyway, but are these "voltage spikes" responsible for some of our fuel injection "brain" failures? Rebuilding the alternator may be good preventative maintenance for the fuel injection "brain" also. It may be good for your sanity as well, since it will keep you from being stranded with a dead battery when the brushes wear out. I don't have experience with the earlier Paris Rohne alternators but I would think that the 100,000 mile frequency would hold true. YMMV.
Earl Gillstrom '88 S4 5 Speed