Need help with my A/C: 2005 Mustang GT

[Dsmdiggler]

If this is the wrong forum, sorry.

I have two questions and I will be as clear as possible. I'm having a couple issues with my A/C, first one being the compressor cycling. When I am driving my car I get a surge from the engine and I can hear the a/c compressor cycling. This is NOT when the car is sitting at a stop light or something, its actually when I am driving the car. I tested the low side and it was at about 30psi, 75 degrees outside. What would make this happen? Low Freon, the cycle switch? Please help, so annoying.

My second question is in regards to the compressor as well. The compressor whines when I have the air conditioning on, if I turn the A/C off the whine goes away. Any ideas, advice? Just an fyi the air DOES blow cold, but something is going on. Any help would be great, thanks much!

Pat

[QuarterHorse]

Without actually seeing the car it's hard to diagnose problems. As a rule of thumb the head pressure (temperature) should be ambient plus 30 degrees. So...at 75 degrees ambient your high side temp should be 105 degrees. My gauge set does not show temp on it so I'd just be guessing on actuall pressure. All my charts are at work. With the low side at 30psi it will cool and not cycle the clutch if the freon charge is correct. One thing to do is watch your low side gauge you have and have someone idle the car up and see what happens to the pressure. I'm not sure what the cut out is on the low pressure switch for that car but if the system is low you will see the gauge drop towards 0psi. When it reaches cut out it will disengauge the compressotr clutch. When the pressure comes back up the clutch will again engauge. Then its possible to be low on freon. The problem with trying to diagnose an a/c problem in a forum like this is that there are too many variables as to what could be wrong. But try watching the gauge and have someone idle the car up and see what happens. This will give you a starting point. As for the noise....not good. Hope this helps a little. I've been doing a/c for 25 years and I've learned one thing...anything could be wrong.

[fazm]

best bet is take it to a shop, pressures will never really tell you how much you have anyway.
cant tell ya how many people come into my shop telling me "my pressure was low, so i added a can, and now its worse"

[Dsmdiggler]

Thanks to both responses.. Do either of you work in a shop I can bring the car to???

[fazm]

i do, sounds like he does to. im in ahwatukee

[QuarterHorse]

Actually I work for a school district and take care of everything vehicle related.

[Dsmdiggler]

i do, sounds like he does to. im in ahwatukee

let me know where and i will call and make an appointment. thanks!

[fazm]

let me know where and i will call and make an appointment. thanks!

ill send u a pm

[1quikv6]

A/c issues, some Fords have compressors that cycle all the time even when A/C is off to keep lubercation to comp. , but should not drop RPM hardly at all when A/C is off. , if you have A/C in mode other than 'Max A/C' it may cycle to control temp. in max A/C it should not.