The A/C is blowing HOT air in my 1996 Dodge Ram 1500 Pickup. The A/C compressor is running, the suction line cools and sweats, the charge and pressures look good. Our family business is mechanical contracting, so I had one of our A/C techs put a set of gauges on the system and he said everything looked okay, that the A/C was working.

What seems to be the problem is that the HEATER is also ON, thus the hot air. Is this possible? If the engine is COLD, I can start the truck and the A/C blows very cool air. After a few minutes, (when the water temp rises) it turns hot. The compressor is NOT kicking out on low/high pressure.

About the time that this starting happening, I noticed the my temperature control knob has a "rough" spot when turning it through the range. Could this be related?

Is there some type of baffle that deverts air through the heater coil? How can I locate or test it?

Thanks for any help.

Most things are set up for the coolant to always flow through the heater core. Before the thermostat opens, the heater acts as a bypass relieving the pressure. There is a door or baffle that directs air through the heater core. It sounds like it is stuck in the heat mode. You might start with the controls. The rough spot could be the cable beginning to slip. If you are lucky it could be as easy as tightening up a set screw in the controls. Otherwise you may have to tear the whole ventilating system apart to find and fix the door at the heater core. I have never worked on a Dodge, and have no idea how much of a job it might be. At least in a truck, you may have more room to work than in a car.

Thanks a lot labman. You were correct. The cable had become loose. Instead of tearing out the whole dash, I had the dealer show me how to switch it manually.

Under the dash on passenger side there is a silver shaft exposed that you can manually turn. It opens and closes the blend door for ac to heat. This happened to me now it works.