So I recently got my CTT back from the dealership who installed a new PCM system. All that works fine...

My problem is that ever since I have gotten it back the 'Mono' functionality of the HVAC system won't work. I hold the 'Auto' button and the 'Mono' light blinks once sometimes and other times does nothing. The Mono mode never initializes. I've tried fiddling with each of the switches to make sure on isn't stuck, tried different settings, etc. to no avail.

Interestingly it DOES go into 'Mono' mode when I adjust the rear controls (4-zone) but shuts off after the 10 second period to adjust the rear.

Any ideas? Hopefully the dealership didn't nick a wire or anything!

Thanks!

 

that definitely sounds interesting. you better have it checked out by an experienced tech guy as this problem sounds hard to diagnose

 

Chalk this one up to an electrical gremlin. All of a sudden it decided to start working again. Something must have been stuck as I "wiggled" the switches perpendicular to their action axis (horizontally)...

Weird.

 

Aren't those gremlins horrible? My reverse sensors acted up a while ago and then they just started working without a glitch and haven't acted up since. So weird.

 

Did you ever have this happen again or find out what it was? Mine did the EXACT same thing, except no one worked on my vehicle. I put on the defrost and pushed the auto button to go back to normal mode and now the mono is doing what you described... Any help would be great.