1983 f250 blowing cold air

[Kody1978]

Hey everybody,

So I have an old 83 f250 with the 5.8 in it. It's winter now, so I am using the heater quite a bit.. The trucks heater works great when it's sitting still or going 40 mph or less. When I get on the freeway it blows straight cold air. And as soon as I get back onto normal streets, it warms up again.. It wasn't doing this last year.

What do you all think it could be? I have checked the coolant level many times and it's good..

 

[Beach66Bum]

This may seem a bit silly, but if your truck doesn't have A/C, there are vents on both sides in the kick panels that may not be closing (or are open, I forgot to close mine when the weather got cold and had this symptom) fully. Also check the ductwork, like where the blower motor box attaches to the firewall. My old f250 let in air there, the foam gasket was worn out.

 

[1970Custom]

Depending on where you're at, a piece of cardboard in front of the radiator can help...

 

[m78]

Fan belt might be loose, if that year has them. Higher rpm on the engine causes the belt to slip on the waterpump and not circulate water.

 

[DNFXDLI]

Coolant level full and thermostat working properly?

Having said that, I don't know where you are located, but when I used to drive vehicles of that era in minus 20 or better, the heater would often blow cold at highway speed and as mentioned, a piece of cardboard across the front worked wonders.