Mechanics

NO HEAT

1998 Ford Ranger

1998 Ford Ranger 4 cyl Two Wheel Drive Manual 106000 miles

my 98 ranger has no heat at all. I've checked the gate, fluid level, and the truck is running at a normal temp. The heater control valve vacuum line has no vacuum on it no matter what the temp control is set at. I've tried manually opening the heater control valve and still no heat. Where does the line connect to once it runs inside the firewall? What would cause the line to lose its suction? How can I test the temp selector knob?
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Bigg_e_n_austin
December 11, 2008.




OPERATION
CONTROL PANEL & DOOR ACTUATORS
Manual A/C-heater control panel is located near center of the instrument panel. A/C-heater controls include a function selector knob, temperature control knob and blower speed control knob. See Fig. 1 . Function selector knob actuates a vacuum selector valve that controls vacuum to door actuators. Door actuators control position of outside/recirculation, floor/panel and panel/defrost doors. Door positions determine airflow modes (panel, floor, defrost, etc.).
Temperature control knob controls an electric blend door actuator. Blend door actuator controls the position of blend door. Blend door position determines airflow around and/or through heater core. Each function selector knob setting affects system operation is as follows:
OFF
Vacuum is applied to inlet duct door, preventing outside air from entering system. Heater water control valve is at full vacuum, preventing hot coolant from reaching heater core. Vacuum is applied to floor/panel and panel/defrost door actuators. Blower motor and compressor will not operate in this mode.
MAX A/C
A/C compressor operates in this mode. Vacuum is applied to air inlet door, preventing outside air from entering system. Heater water control valve is at full vacuum, preventing hot coolant from reaching heater core. Vacuum is applied to floor/panel and panel/defrost door actuators. Airflow exits from panel vents. Blower motor is on.
A/C
A/C compressor operates in this mode. Vacuum is not applied to air inlet door, allowing outside air into system. Heater water control valve is at no vacuum, allowing hot coolant to reach heater core. Vacuum is applied to floor/panel and panel/defrost door actuators. Airflow exits from panel vents. Temperature setting can be changed manually. Blower motor is on.
Vent
Vacuum is not applied to air inlet door, allowing outside air into system. Vacuum is not applied to floor/panel door actuator. Vacuum is applied to panel/defrost door actuator. Airflow exits from panel vents. Temperature can be adjusted manually.
Floor/Panel
Vacuum is not applied to air inlet door, allowing outside air into system. Heater water control valve is at no vacuum, allowing hot coolant to reach heater core. Partial vacuum is applied to floor/panel door actuator allowing door to open partially. Vacuum is applied to panel/defrost door actuator. Airflow exits from panel vents. The A/C compressor operates in this mode.
Floor
Vacuum is not applied to air inlet door, allowing outside air into system. Heater water control valve is at no vacuum, allowing hot coolant to reach heater core. Vacuum is applied to floor/panel door actuator. Vacuum is not applied to panel/defrost door actuator. Airflow exits from floor ducts.
Floor/Defrost
Vacuum is not applied to air inlet door, allowing outside air into system. Heater water control valve is at no vacuum, allowing hot coolant to reach heater core. Partial vacuum is applied to floor/panel door actuator. Vacuum is not applied to panel/defrost door actuator. A/C compressor operates to dehumidify air and reduce windshield fogging. Airflow exits from panel vents and floor ducts.
Defrost
Vacuum is not applied to air inlet door, allowing outside air into system. Heater water control valve is at no vacuum, allowing hot coolant to reach heater core. No vacuum is applied to floor/panel door actuator or to panel/defrost door actuator. A/C compressor operates to dehumidify air and reduce windshield fogging. Airflow exits from defrost outlets.


http://www.2carpros.com/forum/automotive_pictures/266999_vac_2.jpg


Dave H
Dec 11, 2008.


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