Radiators working but no hot water

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I would remove the actuator, and check that the valve works smoothly, maybe turning the stem with pliers. It should only move about 1/4 of a turn. And that the valve stem engages correctly with the actuator, and there is no damage.
Then call for HW, make sure the valve is open manually, and see if the boiler continues to run.

Removed the motor and called for hot water. The motor ran briefly then stopped. Confusingly the manual open lever does not does not reach the microswitch. The new motor should do the trick

 

[fixitflav]

Removed the motor and called for hot water. The motor ran briefly then stopped. Confusingly the manual open lever does not does not reach the microswitch. The new motor should do the trick

Do you mean the valve motor? Did the boiler continue to run, as expected if the valve is open?
The boiler should only run when one of the microswitches is closed.