Access to the heater core is the problem. No real way to test in when installed, and if you pull it, might just as well replace it..... Maybe check inlet/outlet temps on the hoses at the heater core, see how much of a temp difference you get....

One hose should be cold and one hot right? If both hot then that's a problem

One should be hot and one should be cooler. So one on the left you shouldn't be able to hold long, the one on the right (towards drivers side) should be cooler.

Well I guess I'm just bassakwards 'cause you wanna see heat on both. If not, heat's getting to the core but the core is clogged and it's not passing through. Sure, the outlet temp will be a little cooler because the heater core is just a mini radiator, but not by much....and if you have the blower motor off temp drop thru the core will be negligible.

In '96 the heat blend door is cable actuated, no? It's pretty easy to trace it over to the top of the heater box -- I believe removing the glove box gets you eyes on it? I'd at least make sure that's moving as it should and see if you HEAR the door move as you swing the dial. I understand it doesn't completely explain heat at idle and not on the highway, but the last time I had a stuck door on my '95 F250 I had the same symptoms

I thought he was using a infrared thermometer? If that is the case one said will be cooler at full fan speed. 96 is cable operated.

My truck did the same thing for years as his does, only at 35 above, not below. And a new core cured it. He needs a new core.

But at that temp, getting heat will take a looooooong time. I started (unplugged) and drove through -27 F once in South Dakota and didn't have heat for hours.

Just did the heater core. Same damn problem! I'm so mad I need heat!

Thank You for your input. You are correct it is cable activated. I was able to watch it freely move back and forth while adjusting the heat. I just did the heater core. Same problem!!! I'm stumped I need heat! I don't know what else to do ?? Or where to check now

If no air is blowing threw the code it will be basically the same(doubt you could tell the difference just by feeling them). Air takes the heat away cooling the core then you will feel a difference. If both hoses are hot then the issue is in the hvac box. Put it on defrost(default position) at operating temp what comes out the vents(fan on full speed)?

[QUOTE=Moparite;3534517]If no air is blowing threw the code it will be basically the same(doubt you could tell the difference just by feeling them). Air takes the heat away cooling the core then you will feel a difference. If both hoses are hot then the issue is in the hvac box. Put it on defrost(default position) at operating temp what comes out the vents(fan on full





at defrost and at full temperature and speed it blows the warmest at idle it's enough to defrost the windows but not hot as it could be. It's just weird that it gets cooler as your driving.