I have a 98 ranger 4x2 that has a problem with heat. The temp doesn't change when I rotate the control to heat(the red portion of the dial)It blows ac cold air. The compressor has always run even when I switch to heat or defrost. Lately though there is no heat. I would like to know how to test the blend door actuator before I go through the steps advised by "The Heatertreater"

 

After engine is warmed up let it idle and pop the hood.
Turn heat control to HOT
Feel both heater hoses at the fire wall.
If both are HOT then heat control valve/by-pass valve is working.
One might be slightly cooler but only slightly, if it is only warm then valve is not opening all the way, or heater core is plugged up.

If both hoses are HOT then it's a Blend Door problem.

A/C will cycle on/off in defrost for sure, it is used to dry the air blowing on windshield.
It might do that in Heat only for the same reason but not sure on a '98.

 

Thanks for the info. I've narrowed it down to the blend door bot want to trouble shoot the actuator somehow. I have also cut a access hole in the top of the plenum to try and move the blend door so I get heat when I switch to heat. The door doesn't move,like it is being held by the actuator.