The compressor cycles every 5 seconds or so. The low side pressure goes from 45 psi when the clutch is disengaged and 25 psi when it is engaged. This was with the AC on high, doors open and about 80 F outside. The air from the vents was slightly cooler so there is some cooling action but not much.

I was going to add refrigerant, assuming that was why the compressor was short cycling but stopped as soon as I saw these pressures. I began looking for a bad low pressure sensor after reading some of the comments above.

 

What is the high side pressure?

The low side pressures indicate the switch is operating properly but the system is undercharged.

 

You can can loopback the pressure switch simply by taking a little piece of wire (strip the ends back about 1/4"), pull off the connector, and short the 2 points together with it. It should force the compressor to run, but I wouldn't leave there if the pressure doesn't want to maintain, but it seems like a way to get your added coolant circulating. So far I'm having pretty good luck!

 

When I read your comment I realized that you were right and I was reading the gauge wrong. The 45 psi reading was while the compressor was off and the 25 was while the compressor was on...yes at 25 psi it was undercharged.

I've added refrigerant to 45 psi and the cycling has stopped. The duct air temp has dropped from 90 F to 69 F (ambient was 91 F here in sunny Michigan).

Thank you for your help.
Chris Z

 

Thanks for the reply, when I added the refrigerant it took a couple of minutes but as the pressure built each cycle was a little bit longer until the compressor stayed on. It's charged to 45 psi now and is cooling.

 

Sounds closer to normal now. Still has problems as you should be able to hit temps in the 40s.

 

Yep. Not quite there although working better. I'll keep digging and repost if needed. Thanks again.

CZ