Oh, and another dumb question - what if I find my pressure is off - how do I fix it without losing my charge or is that possible?

 

When your system is off for a period of time, the High and Low sides will both equalize through the metering device, in our case the H-valve.

On fractional HP compressors the compressor can have a hard time restarting if the pressure is NOT equalized, this is why you have to wait 3 minuets when you cycle your home HVAC unit. I have installed delay on make timers to delay the restart and Kick Start capacitors to jump start the compressors.

On our trucks all you need to do is to make sure the sight glass is full and there are no bubbles or streaks of oil.

Unless there is some component failure, all you should have to do is to keep the refrigerant full, on a mobile system it is always going to leak down because of the mechanical seal on the compressor.

If you need to open the system to replace a part then you need a recovery machine to remove the refrigerant, clean it and charge it back into the system when you are finished.

Jim