2001 mercury sable heating malfunction

You're out of engine coolant causing the overheat. No coolant to circulate into the heater core, you won't get any heat from the heater. Refill the radiator and find the leak. Fix it.

check fir vacuum hose condition to the vent/heater controls. Hot water controls that are not used on a regular basis corrode up and jam so check out the control/tap

First make sure you dont have an air lock in your heater core and make sure you feel heat from the two heater hoses if you do fell heat your problem is under dash. If the hoses are not hot you have a blockage some where you may have a heater valve not operating it works by vaccum if u have AC look in the engine compartment or it maybe under the dash by heater core, I belive its in engine bay by Ac and heater boxes

Joe

Is coolant level OK? if so could be a bad thermostat. check the heater hoses from engine to heater core. they should be both hot at operating temperature. if one is and one is not then it would indicate a restriction in the heater core. if the lines are not hot then try the thermostat.let me know how you make out.

There are baffles in the heater box that switch from AC to Heat - could be stuck in the AC position.

It can come and go. It sounds like the blower might be bad.

http://www.car-stuff.com/repairmanual.htm

It's quite possible that it's low on coolant. The heater core is the first thing to suffer from lack of coolant. If it's not low, then the heat control is probably malfunctioning.

The clicking noise is the motor for the "blend door". The heater core and the air conditioning side share the same ducting. When you move the knob a small motor moves the door letting the respective hot or cool flow happen.
The heater core is probably blocked. The engineers at Ford have the coolant hoses bypassing the core with a WYE at the firewall. The coolant takes the path of least resistance and stops FLUSHING the heater core and it eventually clogs.

were is the auto senor for the headlights in a 2002 mercury sable