what would cause the voltage guage to fluctuate?

[blink327]

My voltage is never constant, its low a lot, then moves around a bit once the ac is on. Does anyone know what is causing this??

 

[Rootus]

Do you have underdrive pullies? Either way, movement of the voltage gauge is normal when you have a high load. When the A/C is on, the engine fan comes on as well which puts a noticable load on the electrical system. Then add in things like the blower fan for the vents, and headlights if it's dark outside, etc.

 

[blink327]

Do you have underdrive pullies? Either way, movement of the voltage gauge is normal when you have a high load. When the A/C is on, the engine fan comes on as well which puts a noticable load on the electrical system. Then add in things like the blower fan for the vents, and headlights if it's dark outside, etc.

yes i do have underdrive pulleys, as well as h/c/i.

 

[HISSIN50]

does it jump around with nothing else changing (i.e. at idle in the garage, does it fluctuate)? whenever RPM or load change, it will fluctuate, but with no other changes, it should be pretty constant.

good luck.

 

[blink327]

if its just sitting idling its fine. I just dont know why i'll start the car one day and its fine. Then i'll start it again 10 mins later and the voltage is low and stays low? Could it be a bad alternator? Or bad batt connections?

 

[Rootus]

if its just sitting idling its fine. I just dont know why i'll start the car one day and its fine. Then i'll start it again 10 mins later and the voltage is low and stays low? Could it be a bad alternator? Or bad batt connections?

With underdrive pullies, that sounds normal -- for example, when I start my car cold, the idle is high enough to keep the voltage constant. However, after it is fully warmed up the idle isn't quite high enough to keep the voltage steady if there is any kind of load (i.e. cooling fan running or headlights turned on). It sounds to me like you're just seeing normal behavior for underdrive pullies. Be happy that you have an SN95, the Fox bodies have tiny little alternators in comparison, and a whole lot more trouble with underdrives.

Dave

 

[blink327]

Well that makes me feel better. Thanks for the info canary

 

[KeithStang]

Would a Higher amp alternator make up for the voltage flux? I have the same problem and U/D pullies. I was seriously thinking about picking up a 200 amp alternator. Sorry for robbing your post.

 

[HISSIN50]

underdrives still have an effect, even on high output alts - depending upon where your idle is set, too. however, since it is inconsistant, i would double check the connections. a loose wire on the alt or elsewhere in the system, can create freaky fluctuations (dont ask how i know).

H.C's observations sound right on. thanks for the reminder about the puny 65 amp alt the foxes have. with the turn signals on , i watch the Aftermarket gauge dip 1-2 volts each time the TS comes on. LOL. not accurate, but still disconcerting nonetheless. LOL.