CM907 Always on, no flame.

[Cohenpol]

Hello all

I've looked for this fault in previous threads but can't see it.

My 907 controls the upstairs circuit of CH and has worked fine for around 3 years. Lately, somethings been telling the boiler to fire as upstairs is like a furnace without a flame symbol. An example is the target at 19, actual 23, no flame icon but the boiler is on.

The downstairs is a different control panel which has as a red led for HW 'on' and downstairs CH 'on'. I know when the boiler is fired up for upstairs as neither of these leds are on.

I've changed the 907 but the problem still exists. The only way to turn the boiler off via the 907 is to move through slider to 'off' or increase the target temp to above the current actual shown then back down again. The down click removes the flame icon and the boiler turns off.

Any ideas? Another 907 incase I had a bad batch or wiring? Where does the wiring from the back of the 907 go to? Is this a problem outside of the 907? The downstairs CH and HW are working fine.

Any help is appreciated.

 

[picasso]

The upstairs 2 port valve is stuck on.

 

[Dan Robinson]

Or the 907's relay is guffed.

 

[DP]

OP, check system fuse. Sometimes 13 amp fuse in place that can cause problems if short circuit occurs. Fit 2amp if you can get that fuse, 3 amp normal, 5 at a push.

 

[Cohenpol]

Or the 907's relay is guffed.

Thanks Dan, where is the Relay?

 

[Cohenpol]

OP, check system fuse. Sometimes 13 amp fuse in place that can cause problems if short circuit occurs. Fit 2amp if you can get that fuse, 3 amp normal, 5 at a push.

Cheers, where do the fuses live?