* Low coolant level: The coolant level may be low, which will cause the heater core to not receive enough hot coolant to heat the air. Check the coolant level and add more if necessary.
* Faulty thermostat: The thermostat may be stuck open, which will prevent the engine from reaching its normal operating temperature. This will cause the heater to blow cold air. To check the thermostat, remove it and place it in a pot of boiling water. If the thermostat opens, it is good. If it does not open, it is faulty and needs to be replaced.
* Clogged heater core: The heater core may be clogged with sediment, which will prevent it from transferring heat to the air. To clean the heater core, flush it with a hose and water.
* Faulty blend door: The blend door may be stuck in the wrong position, which will prevent hot air from flowing through the heater vents. To check the blend door, move the temperature control lever from hot to cold and listen for the sound of the door moving. If you do not hear the door moving, it is faulty and needs to be replaced.
* Other issues: Other potential issues that could cause the heater to blow cold air include:
* Vacuum leaks
* Faulty heater control valve
* Faulty water pump
* Failed head gasket
Temperature Gage Not Working
* Faulty temperature sensor: The temperature sensor may be faulty, which will prevent the temperature gage from receiving an accurate reading. To check the temperature sensor, disconnect it and connect a voltmeter to the terminals. If the voltmeter reads 0 volts, the sensor is faulty and needs to be replaced.
* Faulty wiring: The wiring between the temperature sensor and the temperature gage may be faulty, which will prevent the gage from receiving an accurate reading. To check the wiring, inspect it for any damage. If you find any damaged wiring, repair it or replace the wiring harness.
* Faulty temperature gage: The temperature gage itself may be faulty, which will prevent it from displaying an accurate reading. To check the temperature gage, connect a voltmeter to the terminals. If the voltmeter reads 12 volts, the gage is faulty and needs to be replaced.
If you are unable to diagnose and repair the problem yourself, it is recommended to take your vehicle to a qualified mechanic for further diagnosis and repair.
