My A/C had a loose connector that was weeping refrigerant over the course of a year. I've tightened it and added R-134a to bring it back up to level, but the compressors spins for a half a second, my pressure drops to 25 and the compressors kicks off....pressure builds, hits 45 and repeats....lasts for half a second and when the pressure goes below 25, the compressor shuts off. I have plenty of air flow and refrigerant. Maybe I need PAG oil??

 

Something in the system may be plugged up. Maybe the reservoir/dryer.

 

It's still low on refrigerant.

Unless you completely evacuated the system and recharged by weight to the correct amount, you have no clue how much is in there.

 

You need to evacuate the system, verify no leak and then recharge based on the amount required on the sticker under the hood.

If this is a 2008 or older, I would also replace the fixed orifice valve while the system is evacuated.

DO NOT USE ANY OF THAT LEAK STOP STUFF!

 

You don't need to empty the system. You need to put the ac gauge set on it so you can measure suction and discharge pressure and charge it fully.

 

if he wants a correct charge as required by the manufacture he does. There is no way you can tell , exactly, by attaching gauges whether you have: 1.0 lb, 1.2lb or 1.5lb or more.

The only way to be sure you are charged per specs is to reclaim and recharge by weighing in or use of expensive machine that measures.

 

Add another can of Freon. The amount of charge is determined by the difference of pressure between the high pressure and low pressure and ambient temperature.
YOur problem is the low pressure switch kicking it out. You don't have a blockage unless the high pressure line is going about 300 on a warm day (about 80" or so).
Just a general rule you need about 30# on the low pressure line at 2000 rpm. That is if you are not checking the high side. With it kicking out on the low pressure switch, another can of freon is not going to hurt it.

 

Yeah, okay. If you want to get it exactly to the ounce. I've been charging AC systems for about 40 years using a gauge set. A few times I had replaced a component and knew exactly how many cans to put in the system but most of the times. I was adding and just used the gauge set. It ain't that hard.

 

I added some and it temporarily fixed the problem, but it has since leaked out I'm not too worried since the plummeting temps

 

The AC compressor works on the defrost cycle too to take out the moisture in the air. So, it is still needed although not necessary.

 

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