I have a mercury mountaineer 2003 V6. It has a problem of making sound repeated when I want to have heat turned on. No sound when the dashboard A.C/Heat stays at AC level, which is the zero? level. The sound is tuk, tuk, tuk, tuk every second not a continous howling on Please help. Jake.

When the engine is cold,check the coolant level.

Make sure it's on max.

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A coolant system should be flush every two years.

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If you did a coolant flush recently then air pocket can be the cause of the un-even heating problem.

The DIY method is to drive you car onto a ramp or a steep hill.

Iet the engine cool off and top off the coolant tank.

Set MAX heat + MAX fan

Let the engine ran for 20 minutes wih the cap off and the trap air will escape from the coolant reserve tank,

Check coolant level and top off coolant when the engine cools down.



A shop will charge $75+ for this but using an air operated excavate tool!

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A car with over 90K miles may experience linkage problem to the heater control valve.

The heater control valve (near the firewall) may be stick over time.

Open the hood and move the heater to max and min. Back and forth.

Clean and lube the linkage with WD-40 to free the heater control valve.

If it's a vacuum type heater control valve then cash for leaky vac. hoses.


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Move the fan switch back and forth to re-new the electrical conductors.

Pass a vacuum over the control panel to prevent dust build up behind the console.

System Airflow Description — Manual Climate Control
MAX A/C
When MAX A/C is selected:

• The recirculation door vacuum control motor is at full vacuum, closing off outside air and admitting only recirculated air.
• The panel door vacuum control motor is at full vacuum and the defrost door and floor door vacuum control motors are at no vacuum, directing airflow to the instrument panel A/C registers. A small amount of airflow from the floor duct, defroster duct and side window demisters will be present.
• If the vehicle is equipped with a heater control valve vacuum switch, the heater control valve will be at full vacuum when the temperature selection is in the full COOL position, preventing the flow of hot coolant to the heater core. Blended air temperature is available. For additional information regarding the heater control valve vacuum switch, refer to Section 412-04 .
• If the vehicle is not equipped with a heater control valve vacuum switch, the heater control valve will be at full vacuum at all times, preventing the flow of hot coolant to the heater core. Blended air temperature is not available. For additional information regarding the heater control valve vacuum switch, refer to Section 412-04 .
• Air will be drawn from the recirculated air inlet by the blower motor. When the temperature selection is in the full COOL position, the airflow will be diverted past the heater core and then into the passenger compartment through the instrument panel A/C registers.
• The A/C request switch will be illuminated and will be disabled.
• The A/C compressor will operate if the outside temperature is above approximately 6°C (43°F).
• The blower motor is on.
• The auxiliary blower motor is enabled, if equipped.

• The recirculation door vacuum control motor is at no vacuum, admitting only outside air into the passenger compartment.
• The panel door vacuum control motor is at full vacuum and the defrost door and floor door vacuum control motors are at no vacuum, directing airflow to the instrument panel A/C registers. A small amount of airflow from the floor duct, defroster duct and side window demisters will be present.
• The heater control valve is at full vacuum when the temperature selection is in the full COOL position, preventing the flow of hot coolant to the heater core. Otherwise, blended air temperature is available.
• The A/C request switch will be enabled. The A/C compressor will operate and the indicator will be illuminated if the A/C request switch is selected and the outside temperature is above approximately 6°C (43°F).
• The blower motor is on.
• The auxiliary blower motor is enabled, if equipped.

• The recirculation door vacuum control motor is at no vacuum, admitting only outside air into the passenger compartment.
• The panel door and floor door vacuum control motors are at full vacuum and the defrost door vacuum control motor is at no vacuum, directing airflow to the floor duct and the instrument panel A/C registers. A small amount of airflow from the defroster duct and side window demisters will be present.
• The heater control valve is at full vacuum when the temperature selection is in the full COOL position, preventing the flow of hot coolant to the heater core. Otherwise, blended air temperature is available.
• The A/C request switch will be enabled. The A/C compressor will operate and the indicator will be illuminated if the A/C request switch is selected and the outside temperature is above approximately 6°C (43°F).
• The blower motor is on.
• The auxiliary blower motor is enabled, if equipped.

• The recirculation door vacuum control motor is at full vacuum, closing off outside air from entering the passenger compartment.
• The defrost door vacuum control motor is at full vacuum and the panel door and floor door vacuum control motors are at no vacuum, closing off airflow to the defrost duct, side window demisters, the floor duct and the instrument panel A/C registers.
• The heater control valve is at full vacuum when the temperature selection is in the full COOL position, preventing the flow of hot coolant to the heater core. Otherwise blended air temperature is available.
• The A/C request switch is disabled.
• The blower motor is off.
• The auxiliary blower motor is disabled, if equipped.

• The recirculation door vacuum control motor is at no vacuum, admitting only outside air into the passenger compartment.
• The floor door and defrost door vacuum control motors are at full vacuum and the panel door vacuum control motors are at no vacuum, directing airflow to the floor duct and the defroster duct. A small amount of airflow from the instrument panel A/C registers, defroster duct and side window demisters will be present.
• The heater control valve is at full vacuum when the temperature selection is in the full COOL position, preventing the flow of hot coolant to the heater core. Otherwise, blended air temperature is available.
• The A/C request switch will be enabled. The A/C compressor will operate and the indicator will be illuminated if the A/C request switch is selected and the outside temperature is above approximately 6°C (43°F).
• The blower motor is on.
• The auxiliary blower motor is enabled, if equipped.

• The recirculation door vacuum control motor is at no vacuum, admitting only outside air into the passenger compartment.
• The floor door vacuum control motor is at full vacuum and the defrost door and panel door vacuum control motors are at no vacuum, directing airflow to the floor duct, the defroster duct and the side window demisters. A small amount of airflow from the instrument panel A/C registers will be present.
• The heater control valve is at full vacuum when the temperature selection is in the full COOL position, preventing the flow of hot coolant to the heater core. Otherwise, blended air temperature is available.
• The A/C request switch will not illuminate and will be disabled. To reduce fogging, the A/C compressor will operate automatically if the outside temperature is above approximately 6°C (43°F).
• The blower motor is on.
• The auxiliary blower motor is enabled, if equipped.

• The recirculation door vacuum control motor is at no vacuum, admitting only outside air into the passenger compartment.
• The floor door, panel door and defrost door vacuum control motors are at no vacuum, directing airflow to the defroster duct and the side window demisters. A small amount of airflow from the instrument panel A/C registers and floor duct will be present.
• The heater control valve is at full vacuum when the temperature selection is in the full COOL position, preventing the flow of hot coolant to the heater core. Otherwise, blended air temperature is available.
• The A/C request switch will not illuminate and will be disabled. To reduce fogging, the A/C compressor will operate automatically if the outside temperature is above approximately 6°C (43°F).
• The blower motor is on.
• The auxiliary blower motor is enabled, if equipped.