2008 Civic LX

My sister's car lost all the refrigerant when one of the rubber AC hoses that plugs into the condenser, developed a hole in it after being allowed to rub on the radiator fan housing. We replaced the hose, charged it up, it ran cool for a week and then stopped blowing cold air (I have a leak detector ordered and on the way). I checked the pressure on the low side...there was 0 pressure. But the confusing thing... is that even with no pressure, my AC compressor still kicks on (there is some pressure on the high side however... I would assume from the store up pressure created by the compressor running). So my questions is... would this indicate that the pressure switch is defective? Are there other possibilities other than just the switch being defective for the compressor coming on even though there is not refrigerant in the system?

 

How did you do a charge? Proper evacuation and charged by weight with a scale? Or kind of guessed with 12oz walmart death cans? Was that pressure checked with an A/C manifold set or a walmart charge thingy?

0 psi on the low side, and pressure on the high side suggests that there is still enough refrigerant in the system to work. A bad pressure switch is a possibility for it still running, but a more likely scenario is you're low on refrigerant or you somehow got a foreign object that clogged up the expansion valve when that hose burned through. If you didn't vacuum it properly, this clog can also be ice forming internally on the valve. With a clog, it will go to 0 psi or a vacuum on the low side and the high side will skyrocket since it doesn't really have anywhere to go. A low refrigerant charge would make both sides too low.

It's entirely difficult to judge the performance of the A/C system without knowing the ambient temperatures, humidity, amount of charge in the unit, and if the fans all work. We need a little more info on your ambient temperatures, if the car is in sunlight, vent temperature and the pressures of the car while running at idle and hopefully 1500 rpm to give you the best interweb diagnosis.

 

Did you pull a vacuum for about an hour before charging to check if it will hold a vacuum and has no leaks after a half hour or so of letting it sit ?