1. Engine Coolant: The engine's cooling system circulates hot coolant (antifreeze and water mixture). A portion of this hot coolant is diverted through a heater core.
2. Heater Core: The heater core is a small radiator located inside the dashboard. It's essentially a network of small tubes through which the hot coolant flows.
3. Blower Motor: A blower motor, powered by the vehicle's electrical system, draws air from outside the vehicle (or recirculated air from inside, depending on the setting).
4. Airflow over Heater Core: This air is forced across the fins of the heater core. As the air passes over the hot coolant-filled tubes, the air is heated.
5. Air Distribution: The heated air then passes through vents directed by the controls (dash vents, defrost, floor vents etc.). You control the temperature and air distribution via the dash controls, which regulate the flow of coolant through the heater core (via a blend door) and the speed of the blower motor.
6. Control System: The controls regulate the flow of coolant to the heater core. A valve (often controlled by a cable connected to the temperature control lever) restricts or allows coolant flow, controlling the temperature of the air. A separate control regulates the blower motor's speed.
Potential Problems:
If your 1991 Ford Ranger's heater isn't working, several issues could be responsible:
* Low Coolant: Check the coolant level in the radiator and overflow tank. Low coolant will prevent sufficient heat transfer.
* Clogged Heater Core: Over time, the heater core can become clogged with debris, restricting coolant flow. This requires replacement.
* Faulty Water Valve: The valve controlling coolant flow to the heater core may be stuck closed or malfunctioning.
* Blower Motor Issues: The blower motor might be burned out, have a faulty resistor (controlling fan speed), or have a problem with its wiring.
* Blends Door Actuator: This motor controls which vents the air blows out of. A faulty one could prevent heat from reaching the vents.
* Thermostat: A stuck closed thermostat will prevent the engine from reaching its operating temperature, resulting in less heat available for the heater.
To diagnose the problem, you'll need to check for proper coolant flow, test the blower motor and its wiring, inspect the control valves and the blend door actuators and potentially consult a repair manual specific to your 1991 Ford Ranger.
