the volts on my alternator gauge are all over the place the last 3 days

all three days I checked twice a day and the battery has a full charge

9 volts is about the lowest i've noticed then way up toward the top of the gauge but not in the red

then last night I heard a little grinding noise like a bearing when i opened the hood definetly coming from the alt.

Besides the grinding noise could my gauge be on its way out?

Should I have the whole alternator rebuilt? whats the proper way to test the alt.

is there a way to test the voltage regulator?

Dont know much about alternators so any advice helps...Thanks

Hello, I'm no electrical guru, but 12 volts is way too low, and the top of the gauge is way too high. Grinding noises are also not good. If cost is a problem, a parts store alternator will get you by. If you can spend a little more, having your rebuilt at a reputable auto electric shop might yield better quality. I've not done it, but I've read about doing the 90 amp Nissan alternator swap here. You could search the archives for more info. 

 

The gauge should be pretty foolproof, but anything made by man is subject to failure. 

 

John

Thanks I did not know about the 90 amp nissan swap and I've had alternators rebuilt and the cost was reasonable in my opinion

good info on the gauge though I am amazed my battery isn't dead yet

Gonna get the alt. rebuilt soon will throw in the alt. off of my parts brat in the meantime

Since the older Subie gauges are not as bullet proof nor quite as accurate, 12-14 volts is a normal reading though generally closer to 12. If you're alt is grinding, good chance it is toast and that the regulator is going out too which would be why your gauge was all over the place. Subie gauges are notorious for reading high or low when they go, but not so much with the jumping around. Start with the alt, and I'll bet you won't have a gauge issue after.

Yup bouncing needle is your voltage regulator about to go poof... Done the alt swap myself only mine was from a Sentra 65amp. Near future there's a 120amp alt I got my eyes on...

Check all the connections of the fusible links under hood, and the big spade that feeds the fusible links box.

 

Also, check the connection of the ignition switch to the harness (6 pole pink)

 

Either of these having bad connection/corrosion/heatwarp will cause the voltmeter to give faulty readings.  This will cause the alt to  sometimes overcharge because the "sense" wire coming from Ig. reads low so the Alt cranks up to try and maintain voltage.

yeah so I got around to putting on my spare alternator and also cleaned up all my connections

Ive got a steady reading now and the main alt. is getting rebuilt at the alternator exchange

good news

I may be wrong, but never forget the "Other" little possible causes. This could have something to do with something as small and hard to find as a simple short, or a loose connection, etc. Some of the most aggravating electrical issues I have ever dealt with on any vehicle had to do with something  like that. - this is just a heads-up, just in case kinda thing...