HI. New to the forum. I have a 2000 Durango and the A/C is not blowing cold air. I have a gauge that I bought at Wal-Mart that i hooked to the low pressure valve and it will read about 35-40 psi. The clutch will kick in and the pressure drops to almost 0 psi. Clutch will disengage and the pressure will go back up and start over again. Any suggestions would be greatly appreciated.

 

Sounds like you are low on freon.

The high side of the low port depends on temperature outside so I can't give you a definitive number but that sounds way to low. Should be closer to 50 and 20.