If there is enough refrigerant still in the system that some is liquid, the low and high side will equalize and the pressure will be somewhat close to outside air temperature. If it's 70 degrees, you could have over 80 pounds of pressure in the system. If you were to bleed off a little vapor, some of the remaining liquid would vaporize and expand causing the pressure to go right back up to where it was. Pressure in the system will not drop until enough refrigerant is gone that what's left is all vapor.
When you run the compressor, the low side will get drawn down to a lower pressure and the high side will go up. The compressor will typically cycle rapidly on and off. If it does not turn on, you may have to jump the low-pressure cutout switch to keep the compressor going.
If the can of refrigerant doesn't empty within a minute, place it in a pot of hot water. Be sure to wear safety glasses at a minimum. A face shield is better. Escaping refrigerant can freeze eyeballs and cause frost bite.
Monday, May 30th, 2011 AT 11:55 PM