RPMS Bouncing W/ AC Turned On

[MIKES3]

One of my co workers came up to me and said his kid is having problems with his Pontiac Sunfire. It has 32k miles on it. I'm being told once he turns the AC on the RPMs start bobbing up and down. Probalby about a 400 RPM difference. Is this an alternator issue or what.

It only happens when the AC is on

Click to read more...

 

[Mook]

my first thought was alternator...but i dont use my AC..ever...so i cant say for sure

 

[PANDA]

One of my co workers came up to me and said his kid is having problems with his Pontiac Sunfire. It has 32k miles on it. I'm being told once he turns the AC on the RPMs start bobbing up and down. Probalby about a 400 RPM difference. Is this an alternator issue or what.

It only happens when the AC is on

That is the problem...

 

[IDAFC21]

it could just be the compressor kicking on and off, my car does that all the time, but only when the compressor kicks on, or off, it doesnt keep doing it while the compressor is running....so if its CONSTANTLY doing it....then i dont know.

and thanks to my solid motor and trans mounts, my hood scoop also shakes violently w/ my a/c on, and my seat vibrates, so, i got that goin for me

 

[mrself2]

its just the car my old zx2 would jump around at idle with a/c on must likey just cheap ass cars do it more then nice ones

 

[EmersonHart13]

I have never noticed it before, but I have noticed a great power boost when you turn the AC off.

I bet the motor has to work that much harder to run the compressor.

John

 

[IDAFC21]

it does take a bit more strain on the engine. i gotta give it a bit more gas in my car to take off then i would w/ the ac off. tho if i floor it all the way its supposed to have a sensor in it that turns the compressor off, but i can neither confirm or deny this

 

[madscientist]

a rapid change in RPM could be caused by compressor cycling but not likely