JoeyStangz00

Alright i got a 2000 Mustang GT...Problem started with my car's RPM's jumping when i put the defroster on, It would jump to over 1200 and then back down. Then i tried the AC because it was hot the next day, Same problem but it would blow warm/cool air. I did some research, possibly the IAC or AC Cycle Clutch switch...changed both. Now the rpms jump to 800 and then down, I recharged the system and still the same issue. I noticed that when it jumps its because the AC compressor shuts on and off causing the jump. Anyone have any ideas why the compressor is doing that and why do i only have warm/cool air comming out?

Thanks

Jay-rod427

When you recharged the system did you have a pressure guage on it? You can also override the pressure switch by putting a paperclip across the therminals of the plug in, if the compressor stays on it is either low on Freon or the Cyclying pressure switch is bad.

My car with everything working properly jumps to about 900 rpm with the A/C on, and back down to 600 when the compressor cycles off.

JoeyStangz00

when i have the gauge on it...it starts low and gets to yellow and drops back down because the ac shuts off and starts back up again.

Jay-rod427

You need to add more Freon to where it will stay up in the Green range when the compressor is engaged. Put the paperclip across the connector when adding Freon so the compressor will stay engaged and pull in the new Freon.

MineralGrey

this can also happen if the system is overcharged as well, the gauges that come with those freon recharge kits are not that accurate, you could also have condensation in the system as well.

I think what your saying is the compressor keeps kicking on and off if this is the case then the reason your getting warm air is because the compressor is not on long enough to cool the air down. This happened to mine as well i just brought it to a local shop and had that completely discharge the system then recharge it and its fine now, only cost about 20.00.

I would also try the paper clip trick on the plug to further diagnose the problem, hope I was of help to you good luck.

JoeyStangz00

when the compressor is engaged it goes all the way to yellow which is past green then when it shuts off it goes back down. But yeah ill try the paperclip trick later today thanks guys.

Jay-rod427

Now I'm confused... The parts store guage goes on the low pressure side of the system and the pressure should go down when the compressor is engaged, this is also the same port to use if you are adding Freon. If you have a high pressure guage it will go up when the compressor is engaged.

The low pressure port is the one behind the Passenger side Strut tower if that helps.

JoeyStangz00

Okay maybe when its the other way around but the gauge goes past the green section of the gauge and into yellow and then it goes back down and starts all over again. So technically i cant get an accurate reading of the freon but if its passing into yellow then theres some kind of problem or its overcharged..its possible that it could go into red but it restarts everytime..and yes im in the right port, when you plug it into the low pressure port theres no consistant reading, it just goes from Zero and gradually goes to yellow and then back down every couple of seconds.

JoeyStangz00

K i got it to work...had someone flush out the system and recharged it and it works fine now...thanks for your input guys.