Just purchased a 2006 tribute and the A/C isn't working. I have checked the voltage at the A/C clutch and it is reading 12+v. I hooked up a battery to the A/C clutch and can hear it engage. I checked the PSI on the low side of the system and am reading between 35-40PSI. Is this correct? The dealer I bought it from said it should be above 60PSI. I am hoping it is just low on refrigerant but am afraid it could be more. Any ideas?