These small motors are powered by 240V AC to rotate a spring loaded gearing arrangement, which in turn, rotates the spindle to open / close the valve.
The motor windings can overheat and break, which is a common fault when motorised valves fail to operate.
To test a synchronous motor:
- Electrically isolate boiler / system controls
- Cut both factory fitted wires exiting the syncron motor (but near to the already factory fitted crimp connections).
- Set multimeter on ohms scale and measure resistance readings through the windings:
- Approx. 2.4K ohms = ok (resistance will vary depending on manufacturer)
- No resistance / Infinity = faulty
Purposely designed insulated wire crimps are easily obtained and must be used to reconnect the broken wires safely.
When replacing faulty syncron motors, the two factory fitted wires do vary in colour (orange, blue and white), however, this will not matter as long as it fits onto the actuator head, designed for this purpose.