My partner pointed out the other day that the volt meter fluctuates a little when under heavy load. For example with the A/C on, fan on HI, headlights on.... it will fluctuate from 12.5-14 volts. I assume this is normal, but I guess I don't know. He says it's a sign my alternator is getting weak, which is very possible as I have ~160k on it. I put a new battery in about a month ago so I assume the battery is just fine. I have no issues, and I want to keep it that way. If it is getting weak, leading up to a failure, I will just replace it now as I am not one who likes to get stranded or postpone future maintenance.

Any thoughts?

Jeff

NEVERMIND, it has become clear my alternator is going bad.

 

Make sure you check the ground between the motor and chassie. Remove both ends and clean the contact area before reinstalling the wire.

 

Maybe mine is old too. When I have the AC on with the fan blowing, it drops a couple of volts. But I don't think it fluctuates. It is just constantly lower.

 

Replacing the voltage regulator with the alternator in the car is pretty annoying. I would give it a 6/10. A new Valeo regulator cost me about 90.00 dollars. I can get a rebuilt alternator for 190-400.00 depending on brand, but I don't want to go through the effort of removing the alternator.

Fluctuates maybe was a bad word. With everything on the volt meter reads around 12.5 at a stop light, with everything off it reads maybe 14.1.

 

12.5 at a stoplight means your reading the battery voltage with little output from the alternator. 14.1 with everything off means the alternator is putting out.

You say you have anew battery but I'd goto AUTOZONE and have the battery checked.. It sounds like the battery is dying and will not hold more than 12 volts but it could be the ground wire between the motor and frame

 

Well with the new parts in it does the same thing But the good news is there is nothing wrong with my alternator/battery. Our 3 series with the same alternator does the exact same thing. Guess we just over reacted to a gauge I never watched before. Under the max load I can throw at the car, the battery was reading 12.6 and our 3 series was 12.6. Both charged to 13.9 with no added load. The battery itself when the car is off reads 12.4, again in both cars.

The good is I have a new brush set in there as the old set was definitely worn down, a new regulator as well, along with piece of mind. Oh and I get to say, I told you so dear.

The bad is I wasted 100.00 dollars to change a part that didn't need to be changed (yet).