Help. Danfoss boiler programmer not working

[Dougster78]

Hi all. I have an old Servowarm Elite 50 electronic boiler that's worked perfectly well up to now. The problem was noticed yesterday. The boiler programmer which looks identical to a Danfoss FP975 started showing a flashing battery and none of the commands would turn the heating on. I've seen the flashing battery before when mains power had been removed. I've checked the in line fuse and that's good. I removed the programmer from the boiler and although it says Servowarm on the front the sticker on the rear says Danfoss Randall but I can 't make out a model number. The wallplate terminal identification shows N L 1(HW OFF) 2(CH OFF) 3(HW ON) 4(CH ON). Dies anyone know a compatible programmer or what model this is? It looks like there's a blown resistor on the pcb but due to the burning I can't make out the resistor value or I'd try replacing it. Any ideas on what I can do? For some reason I can't attach photos. I notice that the Danfoss FP975 has terminal identification NL123456.

 

[DP]

There is no power at the programmer. Another thing that causes this is a 13amp fuse and a boiler fault. Instead of fuse disconnecting, the pcb inside the programmer disconnects. Nett result is power on the backplate but no power to timer electronics so battery symbol flashes as battery is not being charged.

 

[Dougster78]

Thanks DP. I just checked that the fuse is a 13 amp but continuity test confirms that it's ok. Should I replace the fuse with a 3 amp? What else can I do? Last resort is to contact Servowarm but think that will be expensive.