Test Gauges

By 6 April 2015

The manifold gauge set is unquestionably the most important tool used in air conditioning system servicing. Nearly all service work performed on automotive air conditioning systems requires the use of test gauges. Test gauges enable a technician to determine the system’s high (head) pressure side and low (suction) side vacuum, determine the correct refrigerant charge, perform diagnosis procedures and help determine whether the system is operating efficiently.

Because pressures must be compared in order to determine how the system is operating, the gauge set is designed to allow both the high and low sides to be read at the same time.

1 A hand valve for the low side of the system
2 A gauge for the low side of the system
3 A gauge for the high side of the system
4 A hand valve for the high side of the system
5 A valve for attaching the high side service hose
6 A service valve for attaching devices such cans of refrigerant and vacuum pumps
7 A valve for attaching the low side service hose

1 A Schrader valve allows you to purge the hoses or evacuate the system without interfering with the regular center service hose and also provides a place to hook up the low side hose- when it’s not in use – to keep it clean (the valve on the other end protects the high side hose)
2 A “sight glass” in the front of the manifold allows you to visually monitor the condition of the refrigerant as it passes through the manifold (a nice feature, since a lot of newer systems don’t have a sight glass anymore)
3 To reduce the likelihood of turning a valve the wrong way, the hand valves are mounted on the front of the manifold
4 A T-type center service valve allows you to access both vacuum and refrigerant at the same time