-15* here (yes)
On my 92 f150, I've had the same problem twice. The air temp is regulated by a baffle beside the heater core which controls how much air passes through the core and and how much bypasses, thereby controling the temp. Somehow, I have twice had pens (kids no doubt) drop through the deforst on the passnegers side. They go strait down to this baffle, causing it to not close all the way. When it is open, it is sucking outside air and bypassing the heater core, hence the air is cold. If you take off the cover under your dash that covers the heater core, the baffle will be to the drivers side of it. Make sure when you turn your temp control to hot it closes tightly, being perpendicular to the firewall. Hope this helps. This is all assumig a '97 uses the same theory as the 92-96 styre.
Also, on a lot of these trucks this "baffle" or blend door is vacuum controlled. Make sure the vaccum line and vaccum diaphram are working. On my F150 the soda straw vaccum line to the blend door diaphram broke and the default setting is cold air. I have to tie the blend door control arm back with a string to get any heat in the cab.
Mark
Dave wrote:
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