A/C was putting out hardly any cool air. Got an A/C Pro kit: 20 oz bottle with guage. The guage has you set it according to the air temperature. When I used the A/C Pro kit, lots of cool air came out the vents; however, according to the guage, the pressure was just barely touching the green mark and barely inside the lowest line of the temperature adjustment. The 20 oz can got used up. I got cool air but figured more pressure to get it a bit more in the green would be better.
So I got another can of A/C Pro (just the can since I already had the guage and hose from the first kit). That got the pressure to a tad into the green but wasn't a drastic change. The problem right after adding the 2nd can was I could hear a recurring whine inside the cabin. About every half minute there was a solid pitched whine. It'd come, it'd go away, but it was periodic. I also think there was a bit more of a clunking noise in the engine compartment but I'm not sure it if was just the engine at low idle not being smooth.
I read the instructions and do not recall them even telling me to charge the hose. That is, to attach the hose and guage, press in with something on the end of the hose to open the valve at the end, and squirt a charge from the can into the hose and then release the valve pin to shut it. So what happened is twice there was air in the hose that got injected into the car's A/C system. I don't think air in the A/C is a good thing.
So what could be the whining that I hear inside the cabin? Is it the air getting pushed around in the lines? Might it be the lube and sealant they mix in with the refridgerant?
I don't how accurate is the guage that comes with the A/C Pro kit. Maybe it's defective and I've got way too much coolant (pressure) in the system. In that case, maybe I could bleed some out. My recollection is
50 PSI is about right but I never got that close according to the guage. That's at high temperature. When I filled the first time, the temperature was 80F. The second time it was 70F.At this point, discharging all the refridgerent from the car's A/C (assuming I can just press in on the valve to release the stuff, like a pin valve in a tire valve) and refilling it but this time pre-charging the hose. The first charge was $45 for the A/C Pro kit w/guage plus $15 for the 2nd can, for a total around $70. The car shop says they'll evacuate and recharge for $70-$120.
I have no way to evacuate the system (depressurize to remove water) and just did a simple recharge. I believe they said they'd evacuate at the price range they quoted (which fluctuates depending on how much freon they have to add). As I understand, there is a ultraviolet dye in the coolant that will let them find a leak. I have no UV lamps. So I might just let the shop do it.
I was curious as to what [bad] effect might be caused by injecting the air in the filler hose into the A/C system (and did it twice). And what might be the cause of the in-cabin periodic whining when the A/C is on after my recharging.