When I bought my truck in April the PO said that there was a small leak in the A/C and he would just have to put 1-2 cans in it at the start of every summer. That is what I did this summer and it was blowing cold and working great until about a week ago. I put my pressure gauge on the low side and it has basically zero pressure in it now. I took a wrench to all my fitting to make sure one hadn't loosened up and noticed that the pressure sensor on the cansiter (left side in the picture) doesn't fully tighten. It will loosen but will not tighten down snug, it just spins. Is there an o-ring in there that it is supposed to tighten against? You can wiggle the sensor and hear freon escaping from around the fitting.

 

Probably is an O ring used for sealing. Since the freon is gone I would pick up a new sensor and replace it and then re charge the system. I just checked mine and it is tight so that is your culprit.

 

Alright, I will have to pull it off and see whats going on, thanks.

 

Don't get it too tight, it will crack the new one, use a new o-ring, there is a valve core in there to keep from loosing all your pressure, I even put a little silicon on the threads so help seal it.

 

So is that most likely what happened? Someone overtightened the old one and cracked it? The sensor or the o-ring will crack?

 

that "sensor" is the high/low pressure switch

 

Just low pressure switch not high.

 

close enough.

 

Cool, now I know what to ask for at the parts store. Hopefully the problem is on the switch and not the threads on the aluminum canister.

 

The aluminum canister probably is cheaper to replace, they call it the dryer-filter around these parts.