I will try to be as detailed as possible for good help. We bought a 2013 Dodge Durango. No Rear heat. I am able to cycle between top and bottom vents. I can change speeds of air flow. I have checked the blend door actuator. It is opening and closing fine. I checked my antifreeze and it is good. The piping in the back gets hot like it's supposed to. Odd note. I hit it and hot air came out for about 10 seconds.... I don't know if it is supposed to do this, but the blend door opens and shuts periodically. I got a new blend door actuator and already installed it. Thinking it was that. I am at a loss, without tearing the whole fan system apart. I already have all the piping for the air off of it.the front heat works good.