QuestionI have a 99 gmc yukon. My floor vent will blow, even when I have the selector switched to OFF. Even if i have the button pushed to just circulate the air within the truck and not the outside air. When I have the fan on, everything works fine. This is driving me insane, because I hate to have that air blowing on my leg all the time. Please help.
AnswerBryon,
When did this start happening? Has it happened since you've owned the vehicle? Sometimes, bizarre issues like this turn out to be 'features' (I use the term loosely) that the factory didn't deem a problem. That said, it's good to know if there has been a change -- it's especially useful to have another Yukon around to compare, since these things are often not written in the owner's *or* service manual.
Regardless, I've checked for TSB's, and although none speak to this issue directly, there are 2 bulletins (01-01-39-007 and 04-01-39-007) regarding the operation of A/C modes. They state issues that make the control system unresponsive, and often are intermittent. The repairs involve rerouting an electrical harness and replacing the A/C Control Module, respectively. No specifics on any particular malfunction, so it may manifest as a condition like this. However, it's unlikely that it would just exhibit this little symptom. Food for thought, though.
Most often, issues like this point to a failure in a part of the air distribution system. I've seen countless vehicles with mode door actuator/motor problems -- either failed or not 'homed' properly. Sometimes, rehoming (driving the door full spectrum with the Tech2 scantool) a door motor fixes the concern. Something that is getting more prevalent is the problem with the actual door in the case itself. I've seen them broken before (for example, one hinge separated) yet still work at 90% travel. These tend to exhibit other symptoms as well, like a peculiar noise at the end of travel.
As you can see, this resolution will probably result with a trip to the dealer, or a repair shop that's intimate with Yukons. Getting someone that will actually take the time to diagnose this may be more difficult than the actual repair, however. Good luck!
