My valve shows the “mechanical error” symbol (red spanner): what should I do?

The red spanner icon indicates a mechanical error: the valve cannot correctly actuate the valve pin on the thermostatic valve body (stuck pin, insufficient stroke, abnormal resistance, etc.).

1) Remove the valve and check the valve pin

1. Unscrew the valve from the radiator.

2. If your valve uses batteries, remove one battery (to prevent movement during handling).

3. Check that the valve pin is not stuck:

   • press the pin in (or gently tap it),

   • release it,

   • repeat around 10 times.

Important: never pull on the valve pin, as you may damage the valve body.

Expected valve pin stroke

The pin stroke should be approximately:

• minimum 1 mm

• maximum 5 mm

If the pin barely moves or remains stuck, the thermostatic valve body is likely experiencing a mechanical issue.

2) Check that the pin properly shuts off water flow

You want to confirm that:

• pin pressed in → water flow is shut off (you should no longer hear water circulating),

• pin released → water flows (you should hear water circulating again).

Recommended method (with a thermostatic head)

1. Fit a thermostatic head (if you have one).

2. Set it to the most closed position (0 or frost protection).

   • Listen: you should hear no flow.

3. Then set it to the maximum open position (5).

   • Listen again: you should hear water flow.

Alternative (without a thermostatic head)

1. Press the valve pin in yourself (e.g., using pliers carefully, without forcing).

   • Listen: no flow noise.

2. Release the pin.

   • Listen: flow noise should return.

Interpretation

• If this test fails, the valve body is likely faulty.

• If this test passes, proceed to the next step.

3) Refit the valve and run a calibration

1. Refit the valve onto the radiator.

2. Run the valve calibration procedure so it can initialize correctly based on the valve body.

Reference: How do I start the valve calibration procedure?

If the issue persists

If the mechanical error returns or the valve cannot initialize, the valve pin may be:

• too soft,

• too stiff,

• or too short
  to be properly handled by the valve.

In that case, replacing the thermostatic valve body (or consulting an installer) may be required.