Check the following if the coolant heater fails to heat the coolant:

1. Verify that all electrical connections are made
2. Verify that the external power source is providing 110 volts AC.
3. Verify that the coolant heater cord is not frayed, cracked, or split
4. Test the continuity of the heater cord.
5. Replace the coolant heater cord as required.
6. Test the coolant heater for continuity if the external power source and the coolant heater cord are operating properly.
7. Replace the coolant heater as required.