A/C clutch cycling on and off

[David94Mustang]

I'm new to this form so far i'm loving it here I came in to ask this question but got distracted by all the other form topics. So 4 hrs later i'm finally getting to post the main reason I went to the site. I have a 94 Mustang 3.8L I replaced everything myself except for the compressor. I took advantage of Auto Zone loner tool program. Was able to get the gauges and the pump to pressurize the system. Its not driven to much and is garage kept I did the repairs about 2 years ago. But have only put maybe 10K miles on the vehicle since then. I have remote start and when walking up to my vehicle I already new I was having issues. You could hear the idle change every time the compressor clutch engaged and disengaged. It was blowing out somewhat cold air because it would get cold when the clutch engaged. I live in Arizona so its really hot out here right now the temperature that day was 110F. What I noticed is when the system and vehicle is first started you can hear and feel ( by the idle change) the clutch engaging and disengaging. But after about two minutes of driving the clutch didn't disengage at all and the system worked perfect again blowing out ice cold air. I’m just wondering what could cause this issue if you had any ideas. Personally I’m thinking it may be the high pressure sensor that’s attached to the top of the accumulator. If so that would be an easy fix and I wouldn't even need to worry about messing with the Freon at. Is there a way to test the high pressure switch with a volt meter and if so what are the numbers I would look for. In advance I just wanted to thank you for your time I really appreciate it a lot.

 

[luigisho]

I'm no pro at this stuff but fussing with ac systems over the years leads me to start at checking for proper refrigerant charge, then ac pressure switch, and then clutch (gap to engage gets too wide).

If you think you have it right but not really sure, you might consider paying a pro who does it everyday. Some amenities are worth paying for, like climate control, in the season and region where going without can beat you up a little.

 

[Devin]

Welcome to the forum! This forum is mainly devoted to Taurus SHOs of various incarnations, but has a wealth of knowledge that transcends a single trim level.

With that said, it is best to post non-SHO content in the General Chit Chat forum

Speaking of which, I have a battery question...

 

[David94Mustang]

Wow good to know I didn't know about that when I was on this site. Update though about the A/C it seems to only act up when its really really hot outsidde like 108F and my car has to be out in the sun for a bit heating my car up even more for the A/C to act up. I park my vehicle in the garage.

 

[rubydist]

99% of the time the issue you describe is due to the refrigerant being just a little low.

when the a/c is commanded on, the clutch will engage so long as the low pressure switch is "on" and the high pressure switch is "on". the low pressure switch will turn "off" when the low side pressure gets too low, and the high pressure switch will turn "off" when the high side pressure gets too high. normally, the high pressure switch stays "on" all of the time, unless there is a blockage of the expansion valve/orifice tube.

however, the low side switch is also known as the "a/c cycling switch" because in many situations the low side will get pulled down low enough to cause the low pressure switch to go "off" (which turns the a/c clutch off) and then the pressures will equalize for a period of time and then the low pressure switch will turn "on" again. if the system is properly charged, at an ambient temperature above somewhere between 80-90, the low side will stay high enough that the low pressure switch just stays "on" and then the clutch never cycles. if I understand your symptoms correctly, it takes an ambient temperature above 100 before the a/c does not cycle, which suggests that the refrigerant is just a little low.

in any event, what you describe does not indicate anything wrong with the high pressure switch.