Control Assembly: Testing and Inspection
VACUUM CONTROL SYSTEM
Use an adjustable Vacuum Test Set (Special Tool C-3707-B or equivalent) (2) and a suitable vacuum pump (1) to test the heater-A/C vacuum control system.
Place a finger over the end of the Vacuum Test Probe (4) and adjust the bleed valve (3) on the Vacuum Test Gauge to obtain a vacuum of exactly -27 kPa (-8 in. Hg.). Release and block the end of the Vacuum Test Probe several times to verify that the vacuum reading returns to the exact -27 kPa (-8 in. Hg.) setting. Otherwise, a false reading will be obtained during testing.
VACUUM CHECK VALVE
1. Remove the vacuum check valve. The valve is located in the vacuum supply line (black) at the HVAC system vacuum tee.
2. Connect the Vacuum Test Probe from the Vacuum Test Set to the heater side of the vacuum check valve. When connected to this side of the check valve, no vacuum should pass and the Vacuum Test Gauge should return to the -27 kPa (-8 in. Hg.) setting. If OK, go to step STEP 3. If not OK, replace the inoperative vacuum check valve.
3. Connect the Vacuum Test Probe from the Vacuum Test Set to the engine side of the vacuum check valve. When connected to this side of the check valve, vacuum should flow through the valve without restriction. If not OK, replace the inoperative vacuum check valve.
A/C HEATER CONTROLS
NOTE: The operation of the recirculation-air door can be viewed by removing the blower motor and looking up into the HVAC housing.
1. Connect the Vacuum Test Probe to the vehicle vacuum supply (black) line. Position the Vacuum Test Gauge so it can be viewed from the passenger compartment.
2. Place the A/C-heater mode control in each mode position, one position at a time, and pause after each selection. The Vacuum Test Gauge should return to the calibrated setting of -27 kPa (-8 in. Hg.) setting shortly after each selection is made. If the Vacuum Test Gauge cannot achieve the calibrated setting, the vacuum circuit or a component has a vacuum leak. See the procedure in Locating Vacuum Leaks.
LOCATING VACUUM LEAKS
WARNING: On vehicles equipped with airbags, disable the airbag system before attempting any steering wheel, steering column, or instrument panel component diagnosis or service. Disconnect and isolate the battery negative (ground) cable, then wait two minutes for the airbag system capacitor to discharge before performing further diagnosis or service. This is the only sure way to disable the airbag system. Failure to take the proper precautions could result in an accidental airbag deployment and possible personal injury or death.
CAUTION: Do not use lubricant on the switch ports or in the holes of the connector, as lubricant will ruin the vacuum valve in the switch. A drop of clean water in the connector holes will help the connector slide onto the switch ports.
1. Disconnect the vacuum harness connector from the back of the A/C-heater control.
2. Connect the Vacuum Test Probe to each port in the HVAC housing half of the vacuum harness connector, one port at a time, and pause after each connection. The test set gauge should return to the -27 kPa (-8 in. Hg.) setting shortly after each connection is made. If OK, replace the faulty A/C-heater control. If not OK, go to STEP 3.
3. Determine the vacuum line color of the vacuum circuit that is leaking. To determine the vacuum line colors, refer to the Vacuum Circuits Chart.
4. Disconnect and plug the vacuum line from the component (fitting, actuator, valve, switch, or reservoir) on the other end of the leaking circuit. Instrument panel disassembly or removal may be necessary to gain access to some components. See the appropriate service procedures.
5. Connect the test set hose or probe to the open end of the leaking circuit. The test set gauge should return to the -27 kPa (-8 in. Hg.) setting shortly after each connection is made. If OK, replace the inoperative disconnected component. If not OK, go to STEP 6.
6. To locate a leak in a vacuum line, leave one end of the line plugged and connect the test set hose or probe to the other end of the line. Run your fingers slowly along the line while watching the test set gauge. The vacuum reading will fluctuate when your fingers contact the source of the leak. To repair the vacuum line, cut out the leaking section of the line. Then, insert the loose ends of the line into a suitable length of 3 millimeter (0.125 inch) inside diameter rubber hose.