Heater-A/C Controls Test

1. Connect the test set vacuum probe to the HVAC vacuum supply (black) tube in the engine compartment. Position the test set gauge so that it can be viewed from the passenger compartment.
2. Place the a/c heater mode control switch knob to each mode position, one position at a time, and pause after each selection. The test set gauge should return to the 27 kPa (8 in. Hg.) setting shortly after each selection is made. If not OK, a component or vacuum line in the vacuum circuit of the selected mode has a leak. See Locating Vacuum Leaks below.

CAUTION: Do not use lubricant on the switch ports or in the holes in the plug, as lubricant will ruin the vacuum valve in the switch. A drop of clean water in the connector plug holes will help the connector slide onto the switch ports.