I have an 04 FX4 without the center counsel and manual heat ac controls, my issue is when it gets really cold out, the heater will cook my feet on the drivers side, but the passenger side floor is ice cold even with the heater on floor only. I almost feels like there is a draft of outside air coming in to the cabin under the dash. Now i know the blower fan is located under the dash on the passenger side and the fresh air damper is there as well but something just doesn't seem right for that much difference between driver and passenger sides. Any ideas or straight up solutions are welcome. Thanks in advance.

 

I have an 04 XL with the same seat /heater as yours. I've never been on the right side of my truck but my wife (who has cold feet even in the summer ) has never complained. I just asked her and she said, although it could be warmer before she would complain, there is no cold air coming in.

A couple of thoughts....
If you use the recirc button, the heater will pull the cold cab air down to the right side floor making that area colder until all the cab air warms up. That could be a problem but only for a short time.

The whole air system is controlled by electrically controlled doors. If one of them is not opening or closing all the way, you can get air flow where you don't want it. I've seen threads about heat doors not working on this list but if you're getting enough heat on the driver side I wouldn't think that was the problem.

Far too many times I've seen problems with heaters that come from pencils, pens, combs, things that were placed up on the dash and fell down through the defroster outlets, jamming up the air doors. In fact, while replacing the heater core in my 89 350, a mechanic left his pen on the dash and screwed up the heater! I thought it was kinda funny, he didn't!

Other than that, a cracked heater housing, or some other part that is open to the outside.

Bottom line, there's no reason that the right side of your truck should be cold. Hope you find the problem. However, I thought people in Minnesota didn't need heaters!

 

it only does it on long trips or when its 0 or colder. The blower housing and the blower motor itself almost get like cold soaked. It sounds wierd but it blows hot air.

 

I have been into a few dashes where the plastic pipes are not properly fitted together causing a loss of ither climate controlled air or fresh air coming in. I would take a look, a see snake is awesome for this stuff

 

in the summer though when using the a/c, either normal or max, it doesn't blow hot outside air so it is really puzzleing.

 

I was wondering if anyone has had the same problem as Ranger131, because its the same issue I have. I have taken out the glove box and look around and everything seemed fine up there. I have even had my dad drive and stick my head up there driving down the road and couldn't find a draft. I wish I could get it fixed because my feet sweat while the passenger freezes. Thanks for the help