Alternator over charging.

[Install425]

This is the second time this is happening. I installed a rebuilt alternator (1988 930 ) works great for months around town. I sign up for a DE in Sebring ( about 2 1/2 Hrs from home) on the way there alternator is acting up. Charging at 16 volts then down to 11 volts then up to 15 volts back down to 12 volt and so on. I spend the day at the track and this voltage jumping continues. I figure the VR is bad. Get home remove alternator take to shop where I bought and they can not find a problem with it. They decide to give me a new one. I install new alternator, works great problem solved. 1 month later I go back to sebring. Works great all day. Next day I travel to Moroso about 2 Hrs. from Sebring and the alternator starts to do the same thing. Charging to hi then to low but most off the time it charges at 14 volts. I am wondering if the DE events or high RPMs are the cause of my problem. Any input would help. Thanks Rob

[Wil Ferch]

Sounds like more of a voltage regulator problem than a basic alternator problem. The VR shoild never allow over ( say) 14.5-15 volts charge. It might go as high as 14.4 or thereabouts..and that's OK.

Related question...maybe you're putting a severe "recharge" load on your system...like when the car sits for a long ( ~ 1 week +) period and then you start up and drive. The car's alternator is meant as a "topping off" system..and the deep charge demands put on our "garage queen" cars forces the alternator into a heavy-duty mode it was never intended to see. Are you seeing this kind of duty? May relate to cause further alternator / VR problems.

Some on this board have said the replacement HUCO VR is no good..but I've gotten good service from mine. When in doubt , go with the spendy ( 3X HUCO cost) factory Paris Rhone VR. Make sure the "slip rings" aren't too thin where the VR contacts the alternator shaft surface..or at least have your repair guy tell you the condition there. Same with the brushes on the VR that contact the slip rings.

Wil

EDIT: I wrote a technical article in Pelican on alternator / VR R&R..you may want to do this yourself. More and more I'm getting not to trust "others" on their work and expertise. Here's an example of you not "really" knowing what the repair guys did or found.