AC not so AC any more... recharge?

John00Stang · Jun 4, 2009

Sorry to bring this thread up again, but it saved me alot of money. For 3 years my a/c hasn't worked, tried to charge it and even changed the low switch, to no avail. What apparently was happening is... Since i was low on refrigerant, the low side switch was actually working and not letting my a/c turn on, i had to jumper the low switch just to bump up the pressure high enough for the switch to engage the a/c. Hope this thread helps some other people in the future.

Rock777 · Jun 7, 2010

Old thread yet again revived because I really want to say thanks to those that contributed! It helped me pinpoint my problem. I filled the system (or thought I did) with freon, til the gauge showed it was full, but still had no cold air. After jumping the low pressure switch, compressor came on and circulated the freon, which brought the pressure level down because it was very low Air was definitely cooler, now just need a switch and another can of freon.

32ValveRom · Jun 7, 2010

I hope this helps me out. My car's having similar symptoms and I'm a dummy when it comes to a/c. I'll see if I can give this a try

mattlear · Jul 6, 2010

I have a 2001 Cobra that is having A/C problems. Searched the web for folks having a similar problem and stumbled onto this forum.

Problem: A/C blows warm air.
Checked the low pressure /refill port. With A/C not running, pressure seems to be 0.
Turn on car and set A/C to MAX - pressure port shows 25 psi. Compressor kicks on and pressure rises to 45psi then compressor shuts off till pressure hits 25 psi. Cycle continues.

Perhaps I'm not understanding what is happening here. Since the compressor is turning on, and the PSI range seems to be correct (25-45psi) when A/C is engaged, I'm hesitant to add refrigerant (R134A) to the system.

What should the low pressure port show when the A/C is off?

Anyone have any recommendations?

shortygt500 · Mar 18, 2011

Thanks!!!!!

Just wanted to say thanks, this thread totally saved my ass!!!

mattlear: mine was doing exactly the same thing, it would go through that exact same cycle. I bridged the low pressure switch and it got rid of the issue immediately. Currently mine shows 10 psi while the compressor is on and nothing while it's off. About to hit auto zone and grab some r134 and a new switch...

EDIT: Ok so I bought the new switch and it gave me that cycling behavior again. So what I did was bridge the low side switch the way they instructed above with the pics so that the compressor would stay on and the gauge would give me a good reading as I reloaded the r134 into the system. I recharged it to 45 psi and reconnected the low pressure switch and now it doesn't have that off/on cycle behavior. Hope that helps!

cjb56 · May 31, 2011

The AC on my 1997 Mustang 3.8 wasn't blowing cold and the compressor was cycling on and off. Did everything it showed on this thread. The switch change helped and took care of some of the problem. A can of 134a took care of the rest. Now my AC is ice cold! Thanks to everyone on here. You helped a first-timer get the job done and save some money.

Mystic1350 · Jun 1, 2011

AntL97Cobra said:
Hey Shoobs, thanks again for the picture and part number information. Just to make sure I'm understanding correctly, that's the low pressure switch circled in yellow in the picture below??

i dont see the circled yellow switch. i am trying to address this problem on my car and was wondering if someone could please identify where the switch specifically is...thanks!

Jeff1997 · Feb 17, 2012

AntL97Cobra said:
Hey Shoobs, thanks again for the picture and part number information. Just to make sure I'm understanding correctly, that's the low pressure switch circled in yellow in the picture below??

Jeff1997 · Feb 18, 2012

Mystic1350 said:
i dont see the circled yellow switch. i am trying to address this problem on my car and was wondering if someone could please identify where the switch specifically is...thanks!

Just wanted to say thanks for great picture! This switch went out on my 1997 with 90,000 miles. $10.99 at Autozone - part #MT0444. The compressor clutch would not spin, but the engine would surge on & off & on & off. Put the new switch on & worked right away. Also, wanted to point out that too much or too little R134a will cause compressor clutch to cycle on & off.

AC not so AC any more... recharge?

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