chrenan

OK, here's one for the brain trust. Between 4000 and 6000 rpm my voltage guage bounces rapidly up and down. No other running quirks when it happens, everything is normal. Electrical gremlin or a sign of an under/over tightened alternator belt, dying alternator? My car is AC delete and power steering delete, not that I think it matters, but they usually share the same belt.

quinnfiske

Perhaps the voltage regulator is headed south? Does it make a difference if you increase the alternator load? (Turning on headlights, wipers etc)

choinga

...i wouldn't immedately attribute anything weird like this happening on the gauge cluster to an actual problem. My voltage gauge starts right where it's supposed to be on a cold start and then moves down to 12v as the car warms up and from time to time will stay up where it's supposed to be...sometimes it starts up higher than normal, etc... I need to pull the cluster off and clean connection points and replace light bulbs anyway...and now my temp gauge is acting screwy too...

Scott H

When I first got my 951 the volt gauge would never climb over 12v. Took the cluster out to fix the odometer, replace the bulbs, and clean up the connections on the back. Reads about 1 needle width below 14v now, all the time.

Gotta love fixes that just happen.

Ronin-951

Since its happening up the RPM range only, and no other car quirks, I'd clean the Alternator positive/ground first, and if it persists, replace the regulator...sounds like the input filter is going [all in regulator]. The Alternator is OK, so I would pull it and take it to an 'Auto Electric' shop and do a rebuild, [regulator and bearings, diode check] No sense in buying a new Alternator [$$$]

chrenan

Thanks for the input everyone. Voltage regulator was replaced about 3 years ago as part of my regular maintenance to get the car up and running to my liking. I think I'll follow Ronin's suggestion, when winter hits and the car is off the road for the season, I'll pull the alternator and have it rebuilt. I'm sure its original to the car.

dand86951

First clean and check the main alternator cable ends. Then check your ground wires and then under the dash make sure the cluster ground wires are all good.

chrenan

Will do Dan, cluster ground wires are the only ones I haven't
cleaned or replaced since getting the car, so that's top of list.

chrenan

Just thought I'd update this thread in case anyone is searching on a similar problem in the future. I cleaned the grounds under the dash, and while it did brighten my dash lights, it didn't fix my bouncing volt needle. So, a fresh new alternator went in, problem solved, rock steady needle at any rpm. Thanks for the tips everyone.

Also, another great reason to do the AC delete, it took me under an hour to swap an alternator in. That includes jacking the front onto jack stands and pulling and putting away all tools.