We have a Bosch RX2 boiler controller by a Drayton Digistat SCR with the RF3 room stat. The system had been working for several years but recently a problem has started with the red alarm LED on the SCR being on most of the time -- and the room stat not controlling the boiler.

I've replaced the room stat batteries and retrained the SCR. Intermittently the room stat will manage to get a signal to the controller. However, it's not often enough to be useful. (Currently we're using the override button to control the system manually and I've taken the batteries out of the RF3.)

Does anyone have any suggestions?