| Subject: | Blower Speed Changes On Its Own / Manual CJ3 HVAC System |
| Models: | 2004-2007 Buick Rainier |
| 2002-2007 Chevrolet Trailblazer and Trailblazer EXT |
| 2002-2007 GMC Envoy, Envoy XL and Envoy XUV |
| 2002-2004 Oldsmobile Bravada |
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
Blower motor fan speed may change on its own
Recommendation/Instructions:
The CJ3 HVAC system has the ability to open and close the fresh air door at anytime. The purpose of this is to control evaporator temperatures and prevent evaporator freeze. When the fresh air door open/close, this will change air flow rate in the HVAC
case. The blower motor will change pitch and may sound as if it has increased or decrease blower speed. This is a normal condition and no repairs should be performed.
Further, the CJ2 HVAC When placed in manual mode, the recirculation will only work on the Bi-Level settings and will time out approximately after 10 minutes of use or if the ignition is cycled off during this 10 minutes. On ignition cycle, it will be necessary
to press the recirculation button again if this feature is desired. Again, it will operate for approximately 10 minutes.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.
