smokinggoldfish

Thanks ProDave. I took the bypass valve to bits. The drive is a six wire motor, I guess a stepper. There are no switches so I guess the start-up routine is controlled by some software in the main motor module. I don't have a scope so can't see waveforms. I think my options are 1. Buy a new motor module for about £720 (!) or 2. Replace the Heat Rae Sadia unit with that of another manufacturer e.g. Domus or Nuaire for £1000 to £1500 and hope for better reliability. Any comments?

I don't know if this was resolved - but this might be helpful: I have the same problem, and took the motor and bypass valve out of the case to test. The clicking noise is the bypass valve going through a test routine. Once this is done it should send a signal to the motor to start. In my case the valve operates OK but the motor does not run. The fans rotate freely so either the motor has failed or the circuit board (more likely) has failed. But although the board is listed as a spare it is not available, and the only solution is to buy a new motor module complete. I am baulking at the cost (about £700!!!) and have seen elsewhere on this site that there may be some compatibility problems. It looks as though Baxi is just milking this situation. I can't believe that the manufacturing cost of the motor module is more than about £100.