A/T - Checking Pressure Switches For Leaks

TSB 88-7 (Feb)

SUBJECT: Pressure Switch Leaks

CHECKING PRESSURE SWITCHES FOR LEAKS

A simple method to check pressure switches for leaks is to use an air blower with 1/8" pipe thread nozzle fitting. Remove the nozzle fitting from air blower. The thread size of the fitting is the same as most GM pressure switches.




Put a couple drops of ATF into the switch, and tighten it snugly into the air blower. Apply pressure and check for air bubbles. (Figure 1)




Remember some switches have an air bleed. DO NOT MISTAKE AN AIR BLEED FOR AN AIR LEAK. (See Figure 2 - Air bleed.)

Pressure switches should be checked for leaks, because they must hold clutch apply pressure, torque converter apply and release. They also effect computer and emission control systems.

A switch that leaks may not present any problems on road-test (after overhaul), but could cause premature failure of transmission, torque converter, or related controlled systems.