HVAC Mode Switch Inoperative or Stuck in Vent Mode, Oil in HVAC Control Head and/or Vacuum Lines (Replace Transfer Case Vacuum Switch and Contaminated HVAC Components)
| Subject: | HVAC Mode Switch Inoperative or Stuck in Vent Mode, Oil in HVAC Control Head and/or Vacuum Lines (Replace Transfer Case Vacuum Switch and Contaminated HVAC Components) |
| Models: | 2001-2003 Chevrolet Blazer, S10 |
| 2001-2003 GMC Sonoma |
| 2001 GMC Envoy, Jimmy |
| 2001-2003 GMC Jimmy (Export Canada Only) |
| with 4WD and Two-Speed Electric Shift Transfer Case (RPO NP1) |
Condition
Some customers may comment that the HVAC mode switch may be inoperative or stuck in the vent mode. After some diagnosis, oil in the HVAC control head and/or vacuum lines may be found.
Cause
When the transmission or transfer case heat up, the oil may expand and find its way into the transfer case vacuum switch. This oil expulsion may cause the vacuum switch seal to fail and allow transfer case oil to be drawn into the HVAC vacuum lines.
Correction
Replace the transfer case vacuum switch. Refer to the Transfer Case Vacuum Switch Replacement procedure in the Transfer Case sub-section of the Service Manual. Also, replace all contaminated parts in the HVAC system.
Parts Information
Part Number | Description |
|---|---|
15664811 | Switch -Transfer Case Vacuum |
Parts are currently available from GMSPO.
Warranty Information
For vehicles repaired under warranty, use:
Labor Operation | Description | Labor Time |
|---|---|---|
K4120 | Switch, Vacuum Control Transfer Case - Replace | 0.6 hr |
Add | Diagnosis Time | 0-0.3 hr |
Add | With Skid Plate | 0.2 hr |
Any additional time for replacement of HVAC components must be submitted as Other Labor Hours and requires appropriate authorization. | ||
