Central heating pump problem

Bendy_House

Upzeecreek said:

Thanks for all the comments. 
Just to clarify, under normal operation the c on the boiler only appears when there is a call for heat and then when the boiler is lit. When the room stat is up to temp and the boiler isn't required it goes into standby and there is a 0 in the display and pump shut down in airing cupboard. Over run on boiler for 2 mins. 
When it's playing up, instead of going into standby with a 0 , it displays C and pump continues to run in airing cupboard. It still does the over run for 2 mins and goes quiet with C being displayed.
It would stay like this with the pump running for hours if I don't switch off at the wall.
 Turning it back on after an hour will sometimes clear the fault and return the status to 0 on the boiler. 
Programmers are danfoss  62057 ( mains wired)
and danfoss 40704 ( wireless with new batteries) 
Thanks

The prog stats are reasonably sophisticated, but are not Opentherm as far as I can see. So there's nothing 'unusual' about them that could be causing this issue, afaIcs. 

Do you have an outdoor temp sensor?

All I can suggest is a process of elimination as far as you can go. Eg, the next time this issue occurs, press the override button on the 40704's receiver (first of all, note whether the 'on' light is illuminated). Does this cut the pump?

Not sure how to 'disable' the 62057 in the same way - perhaps unclip it off the wall?! See if that stops the pump.

Other than that, I can't see what you can do. Since it is an intermittent issue, I cannot see how it can be a wiring error - it's seemingly been working fine for months before recurring?

It could be soooo many causes - a sticking relay (in the progs or in the boiler), a dry joint on the PCB, a failing component on the PCB (capacitors certainly seem to have a limited working life, and some could affect the operation of the processors), and lawdie knows what else.

Email Danfoss. Email the boiler manufacturer.

Upzeecreek

Just wanted to come back to this and update in case it helps anyone else. 
I did a factory reset of both main and upstairs programmers ( which apparently restarts the microprocessor!) and I've not had a problem for the last 3 months. 

Bendy_House

Jeepers!

Pleased, tho'