* Low Coolant: This is the most frequent cause. If your coolant level is low, the heater core won't have enough fluid to heat and circulate. Check your coolant reservoir and add coolant if necessary (using the correct 50/50 mix of coolant and distilled water). A leak in the cooling system is a serious problem that needs addressing.
* Heater Core Problems: The heater core itself might be clogged, leaking, or failing. A clogged heater core restricts coolant flow, resulting in poor or no heat. A leak will lead to coolant loss and possibly a musty smell inside the car. Replacing the heater core is a fairly involved job.
* Blend Door Actuator Issues: This motor controls the direction of air flow (to the vents, floor, defrost, etc.). A malfunctioning blend door actuator can prevent hot air from reaching the cabin. The actuator might be broken or its linkage might be disconnected.
* Water Pump Failure: The water pump circulates coolant throughout the engine and heating system. If the water pump fails, coolant won't circulate properly, leading to a lack of heat in the cabin.
* Thermostat Problems: A stuck closed thermostat will prevent coolant from circulating to the heater core. A stuck open thermostat might allow the engine to run too cold, but it's less likely to affect the heater directly.
* Blown Fuse or Relay: Although less common, a blown fuse or malfunctioning relay could interrupt the power supply to the heater blower motor or other related components.
* Heater Blower Motor Issues: The motor itself might be failing, brushes worn out, or the resistor pack (which controls fan speeds) could be faulty. This results in no fan operation, regardless of the temperature setting.
* Vacuum Leaks: Some Ford Tempo models use vacuum to control air flow. A leak in the vacuum system can affect the blend doors and heater operation.
To diagnose the problem:
1. Check the coolant level: This is the first and easiest thing to do.
2. Check fuses and relays: Refer to your owner's manual for locations and ratings.
3. Listen for the blower motor: Can you hear it running? If not, check fuses, the motor itself, and the resistor pack.
4. Check the temperature of the hoses going to and from the heater core: If both are cold, there's a problem with coolant circulation (water pump, thermostat, etc.). If one is hot and the other cold, it might indicate a clogged or failed heater core.
If you are not comfortable performing these checks yourself, take your Ford Tempo to a qualified mechanic for proper diagnosis and repair. Improper diagnosis and repair could lead to more serious and costly problems.
