Heater blows hot and cold

[snailwagon]

1981 4x4 pickup, no AC.

When you turn on the heater or defroster, heat will come out through the defroster ducts or through the heater on the very bottom. However, the dash vents and center vent will blow only cold air.

Any suggestions? Isn't there only one fan for the heating/cooling system? It seems wierd that some vents blow cold while some blow hot. The heater valve is working fine, all the heater hoses are also hot. Correct thermostat is in and truck runs at appropriate operating temperature. It's snowing outside right now and I'd like to not have to bundle up in my 4x4.

 

[KLF]

No experience with this vintage, but yeah there should only be one blower motor, so it sounds to me like there is a linkage to a damper behind the dash that has broken or become disconnected.

 

[inkpot]

Howdy! Like KLF says, just check around under the PS dash. there are several little cable/vacuum operated trap doors. One or more of them is not working right. I have the same problem on my 85 because the dash control slide levers have broken away from the inside of the dash, and I am too lazy to tear it out to fix it. John

 

[snailwagon]

On the dash there is a "cold air" lever, at least there is supposed to be a lever there. Is this just a provision for AC (no AC in this truck, ever)?

 

[jkl72-40]

Also check the fresh/recirculation lever if its on fresh and trying to heat it may not work also you may be low on coolant

 

[ajfriz]

My 82 does the same thing and it really sucks when its -10 like this morning...