No heat, clicking sound when turned to Hot , stops when turned to cold.

Sounds like a vacuum hose problem.
Lee

THER SHOULD BE A BLEND AIR MOTOR UNERD DASH THAT CONTROLS HOT AND COLD SOUNDS LIKE THE GEAR IS STRIPED OUT ,NOT EASY JOB TO DO

SOUND LIKE A STUCK BLEND DOOR OR FAULTY DOOR ACTUATOR ELECTRIC MOTOR BAD.

2004 mercury mountaineer.heat problem
When turning ac knob to heat clicking sound like door opening and closing repeatedly sounds and air blows cold instead of hot.

If I understand your problem, what you actually hear is a "clicking" sound. If I am correct, your unit only blows out cold air. If so, your problem is the "Heating & AC blend door actuator. It is a small plastic box that contains plastic gears. The unit receives an electric signal to change positions, but the broken cogs prevent the unit from operating properly. A quick check to determine if this is your problem, turn the heater on. Adjust the temperature from heat to air. At some point the noise will stop.

I have the same problem, I have the dash apart and the blend door actuator is bad causing the clicking sound. The actual door that has been talked about is fine. Although, still no heat, I have another problem.

sounds like it might be low on coolant. Low coolant levels will stop the flow and circulation to the heater core, and also might be the cause of overheating

Heres the answer for the clicking sound

I had the exact same problem, yes it was the heater control valve, the repair was 285.00. The tech that replaced it told me it is a common problem for the Galant. He said that if you keep your temp selector on either all hot or all cold that it keeps constant pressure on the plastic gear teeth in the valve. As they break off one by one you begin to hear that clicking noise as the dont catch. When you finally break off the last one it stops working.

According to him if you always leave the dial at least one notch from fully hot or fully cold you will not experience a failure of the switch

I ended up taking the vehicle to the dealer. The 'blend door' actuator had gone bad (stripped gear?). $66.00 for the part over $330 for labor. The console and part of the dash had to come out.

There is an actuator motor that controls the heater door, when these go bad they make a clicking noise. If the clicking stops or pauses when you change the heat from hot to cold the actuator needs to be replaced. There is no cable on the temp control it is electrical.