Vacuum Control System Diagnostic
WARNING: This page is about a different car, the 2019 GMC Savana 3500, 2019 GMC Savana 2500, 2019 Chevrolet Express 3500, and 2019 Chevrolet Express 2500. However, it is still accessible from the selected car via links, so may be relevant.
| Step | Action | Yes | No |
|---|---|---|---|
DEFINITION: Improper air delivery
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| 1 |
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Go to Step 3 | Go to Step 2 |
| 2 | Did the customer concern mention that the air discharges out of the correct ducts, and then changes during acceleration or higher engine RPM? | Go to Step 7 | Go to Step 3 |
| 3 | With the engine running, cycle the heater and air conditioning control through all the modes. Does the air come out of the selected outlet ducts? |
Go to Step 18 | Go to Step 4 |
| 4 | With the engine running, take a vacuum reading at the manifold vacuum port that supplies vacuum to the heater and air conditioning vacuum control. Is there engine vacuum? |
Go to Step 6 | Go to Step 5 |
| 5 | Repair the no vacuum condition. Is the repair complete? |
Go to Step 18 | - |
| 6 | Take a vacuum reading at the vacuum supply line at the heater and air conditioning vacuum control. Is the vacuum reading the same as the engine vacuum? |
Go to Step 11 | Go to Step 8 |
| 7 |
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Go to Step 8 | Go to Step 11 |
| 8 | Inspect for leaking or collapsed vacuum lines between the engine manifold vacuum port and the heater and air conditioning vacuum control. Are the vacuum lines leaking? |
Go to Step 9 | Go to Step 10 |
| 9 | Repair or replace the collapsed or leaking vacuum line. Is the repair complete? |
Go to Step 18 | - |
| 10 | Replace the heater and air conditioning control vacuum tank. Heater and Air Conditioning Control Vacuum Tank Replacement Is the repair complete? |
Go to Step 18 | - |
| 11 | Using an external vacuum source, apply vacuum to the appropriate vacuum line at the connector to the heater and air conditioning control. Heater and Air Conditioning Control Replacement Does the actuator retract? |
Go to Step 17 | Go to Step 12 |
| 12 | Inspect for leaking or collapsed vacuum lines between the actuator and the connector to the heater and air conditioning vacuum control. Are the vacuum lines leaking? |
Go to Step 9 | Go to Step 13 |
| 13 |
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Go to Step 14 | Go to Step 16 |
| 14 | With the actuator disconnected, inspect the door for binding. Does the door move freely? |
Go to Step 16 | Go to Step 15 |
| 15 | Repair the binding door.
Is the repair complete? |
Go to Step 18 | - |
| 16 | Replace the vacuum actuator.
Is the repair complete? |
Go to Step 18 | - |
| 17 | Replace the heater and air conditioning control. Heater and Air Conditioning Control Replacement Is the repair complete? |
Go to Step 18 | - |
| 18 | Cycle the heater and air conditioning control through all modes to verify proper operation. Did you correct the condition? |
System OK | Go to Step 1 |