Replace the thermostat if it is open at room temperature.
To test a closed thermostat:
1. Suspend the thermostat (A) in a container of water. Make sure that the thermometer (B) does not touch the bottom of the hot container.
2. Heat the water and check the temperature with a thermometer. Check the temperature at which the thermostat begins to open and at which it is fully open.
3. Measure the height of the thermostat lift when it is fully open.
Standard thermostat
| Lifting height | above 8 mm |
| It's starting to open up | 76-80°C |
| Fully open | 90°C |