I was having problems with my air conditioning not blowing cold, so I went to refill my refrigerant, but when i went to read the gauge after 3 minutes of running, the compressor would come on, the gauge would rise to approximately 45 PSI, then the compressor would turn off and the pressure would drop immediately. Is the system overcharged? Or is there some other problem?

 

What side was the gauge on? High or low?

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it was the low pressure valve

 

If the system is to low, there is a low pressure switch to shut down the compressor. Adding coolant will bring it up so the switch stays on. Just follow the instructions on the can and it should work.

 

If the system is too low, find the leak before you refill it. That stuff doesn't wear out or anything. If it isn't charged it's leaking.

 

Only read the gauge while the compressor is ON and your finger is off the trigger to fill the system, dont read the gauge with the compressor off. Once the compressor stops kicking on and off its pretty much full