2004 weird heat issue

I have front and rear climate control. Digital control up front, rotary knobs above for rear.

In the front, I have heat, but no fan and in the rear I have fan but no heat.

I'm really scratching my head on this one. Any help would be appreciated.

Are you hearing any clicking under the dash towards the passenger side?

I have a 05 Deville that had the same issue. it was the valve switch.

It was the module in the duct again. Normally it fails closed but this time it was open. I'm averaging one of these modules a year. Anyone got a solution?

Sounds like it has a crappy ground through the digital control and is shorting out. Instead of using the provided ground through the harness I would ground it directly to the body of the vehicle.

Thanks. I replaced it in April and it's dead again. I may have to reverse engineer my own solution.

It was the module in the duct again. Normally it fails closed but this time it was open. I'm averaging one of these modules a year. Anyone got a solution?

I replaced that actuator in my 2005 Yukon with one from Dorman about two years ago. We had gone 2 years with it switched into the AC mode and then I disconnected the harness to keep it there.

"Loved" that I had to grind down my 5.5mm socket shorter at both ends for access, and the @$^%&*#@$^&*$# hump was still in the way !!! Other type of fasteners would've been easy to do.