Vacuum Test Diagnosis
Step | Action | Yes | No |
|---|---|---|---|
1 | Turn the blower motor fan ON and select an air outlet mode. Does air flow out of the selected HVAC outlet ducts? | Go to Step 18 | Go to Step 2 |
2 | Did the customer concern mention that the air discharges out the correct ducts at first, but then changes during higher engine RPM? | Go to Step 11 | Go to Step 3 |
3 | Cycle the HVAC controls through all the modes. Does the air come out of the selected outlet ducts now? | Go to Step 18 | Go to Step 4 |
4 |
Is there engine vacuum? | Go to Step 5 | Go to Step 17 |
5 | Take a vacuum reading at the vacuum supply line at the HVAC control module. Is the vacuum reading the same as engine vacuum? | Go to Step 6 | Go to Step 9 |
6 | Take a vacuum reading at the output side of the HVAC control module, for the non-functioning mode setting. Refer to the vacuum schematic in HVAC Air Delivery/Temperature Control Schematics to determine the correct actuator operation. Is there vacuum at the output side of the HVAC control module? | Go to Step 7 | Go to Step 14 |
7 | Disconnect the actuator vacuum line and apply vacuum to the actuator. Did the actuator retract? | Go to Step 9 | Go to Step 8 |
8 | With the actuator disconnected, inspect the door for binding. Does the door move freely? | Go to Step 10 | Go to Step 15 |
9 | Inspect for leaking or collapsed vacuum lines. Are the vacuum lines leaking? | Go to Step 16 | Go to Step 13 |
10 | Replace the vacuum actuator. Refer to the appropriate repair: Is the repair complete? | Go to Step 18 | -- |
11 | With the vacuum gauge connected to the actuator vacuum line, turn the engine OFF. Does the system lose vacuum after turning OFF the engine? | Go to Step 12 | Go to Step 9 |
12 |
Does the system lose vacuum after turning OFF the engine? | Go to Step 13 | Go to Step 14 |
13 | Replace the vacuum reservoir tank. Refer to Vacuum Tank Replacement in Heating, Ventilation and Air Conditioning. Is the repair complete? | Go to Step 18 | -- |
14 | Replace the HVAC control module. Is the repair complete? | Go to Step 18 | -- |
15 | Repair the binding door. Refer to HVAC Module Assembly Replacement in Heating, Ventilation and Air Conditioning. Is the repair complete? | Go to Step 18 | -- |
16 | Repair or replace the collapsed or leaking vacuum line. Is the repair complete? | Go to Step 18 | -- |
17 | Repair the no vacuum condition. Is the repair complete? | Go to Step 18 | -- |
18 | Cycle the HVAC controls through all modes to verify proper operation. Did you correct the condition? | System OK | -- |
