System Operation

SYSTEM PRESSURE

Operate system for at least 15 minutes to allow parts to become completely stabilized. Determine if system is fully charged by the use of test gauges and sight glass, if equipped. Head pressure will read from 180 psi to 220 psi or higher, depending on ambient temperature and type unit being tested. Sight glass should be free of bubbles. Low side pressures should read approximately 15 - 30 psi, again depending on ambient temperature and unit being tested.

High side pressure is markedly affected by ambient air temperature. A normally operating system will indicate a high side gauge reading between 150 - 170 psi at 80°F ambient temperature. The same system will register 210 - 230 psi with an ambient temperature of 100°F. No two systems will register exactly the same.

HIGH AND LOW SIDE RELATIVE TEMPERATURE

System high side should be uniformly hot to the touch. Temperature differences indicate partial blockage of liquid or gas at the point of variation.

System low side should be uniformly cool to the touch with no excessive sweating of the suction line or low side service valve. Excessive sweating or frosting of the low side service valve usually indicates the expansion valve is allowing excessive refrigerant into the evaporator.

EVAPORATOR OUTPUT

If system tests and inspections indicate no problems, the evaporator will function to cool the vehicle interior.