No heat in rear of SUV, most of the time

I have a 2004 Tahoe that the rear heat and A/C is giving me fits. I was getting no heat in the rear(front was fine) so I checked the heater hoses to the rear of the vehicle and they get hot. So I replaced the blend door acturator in the rear. That seemed to work for a little while but now it is 50/50 whether you will get heat in the rear. Any ideas?

Did you check to see if the blend-air door was binding? If it is, that could have killed the original actuator, and may now be killing the new one.

I checked that when the new one was installed and that does not appear to be the problem. Thanks

How warm was it when you checked? If you checked it in a heated garage or on a warm day, and now it’s as cold as it is where I live. the contraction due to temperature change could be making it bind if it’s out of adjustment.

Is that actuator vacuum operated? Could you have a leak in a vacuum line?

electric.

electric is correct. I don’t have a garage and it’s been constant temp.(for the most part) for quite a while.