For 1990-2009 cars

1. Verify that the cooling system is properly filled.
2. If the complaint is a low temperature gage reading, check the temperature gage for proper operation. Connect a scan tool to the vehicle and read the system temperature. Compare this reading to the temperature gage. Replace the gage or switch if necessary.
3. If the complaint is no heat from the HVAC system, refer to Heating Insufficient in Air Conditioning.
4. Verify proper thermostat operation. Refer to Thermostat Diagnosis .