Hi, I have no rear heat in my 1999 GMC Suburban. Do these have some kind of control valve that is vacuum operated similar to the front control. It gets no heat to the rear if it is on the "Rear Control" setting or if we attempt to control it from the over head console in the front. One thing I didn't think to check is if the heater piping is warm/hot at the back of the car, but if it isn't flowing I don't really think it could be warm/hot. I know if you plumb the front heater control wrong it will louse up the back. I ruled that out as I have the factory diagram and it is certainly correct up front. Any help would be great!

Vintage 465

 

Is it lack of air flow? Or is it blowing cold air?

 

No it's not lack of air flow, it's blowing cold air.

V-465