Why is it that when I have the heat on only warm air blows and when I'm driving it seems to get cooler and cooler. But I can switch it over to max a/c and it blows out very hot air like it should with the heat on?
I've put two thermostats in it the last being a factory stay. I've also flushed the radiator, put in new antifreeze. Checked the heater core hoses they are both hot after the truck heats up. Any suggestions would be greatly appreciated.

 

If you're getting more heat out of the vents when you change the HVAC control from vent to MAX AC, it sounds like you might have a door sticking in the heater core/AC evaporator box. Drop your glovebox and verify.

 

Are you talking about the blend door? Is it visible by just dropping the glove box? I'm not sure as to what it looks like.

 

The temperature blend door is only one of four doors in the box, and it is cable controlled. With the symptoms you've described, I'd lean toward an issue with the Outside/Recirc door.

https://www.ford-trucks.com/forums/1...l#post13753865

 

Ok, my bad as I didn't give you all of the symptoms. Let me start from the beginning and tell you what I've got. Back in early March I started having a heating problem with only getting warm air. Plus my temperature gauge wouldn't even get to the N in normal. So I change out the stat with one from Advance. Still had the same results after putting back together. So I went to the Ford place and got a factory replacement and when I put it in I also changed the anti freeze and flushed the system good. But still no change. By this time the weather had gotten warm and I just neglected the issue because I didn't have the need for heat. Well this summer when I went to turn on the AC it was hot air. With the mildness of the summer I never looked into it either (don't know if the 2 problems are related) but then as the weather has turned cold again I am left to figure out why I have warm air and my temp hand not warming to normal. Is it possible to be the blend door, or heater core or anything like that since my temp is not in the normal position. Which on my truck should be dead on the R in NORMAL. Seems to me like if it was something around the heater core or blend door, my temp gauge would still heat up correctly.
So far this last 2 weeks I have checked the temp sender by grounding the wire to the truck and turning on the switch. When doing this nothing changed on the gauge so I assume the sender is good. Is this right? Just got done using an infrared temp gun on the thermostat housing and got about 150 degrees. The top radiator hose and got about the same, and both heater hoses. The one on the right facing the firewall was about 150 max and the one on the left facing the firewall 125 max. Don't know how accurate the gun was. Don't see any leaking anywhere, or see any in my oil, but I have to put anti freeze in about every month or so. Cant figure out where its going.
So that's where I am at, any help would be greatly appreciated.

 

I did mention in my first post but will explain again that the other morning with the outside temp about 35 I switched from heat mode over to AC mode and it was way hotter than when in heat mode. Don't understand that one either.