baxi 105 he

[marleyco]

Hi all,
Hopefully a pointer in the right direction.
ABove combi boiler, hot water running at tap, boiler fires up in normal way but no matter what temp its at it heats up to 80 degrees then cut's in and out. I had initialy thought hot water stat. But the same happens on heating. No flashing lights or error's. Maybe a bit unlikely to be both stats.
I didn't have much time to start fault finding today so will be going back. Was hoping someone has had the same problem. Making my day go smoother.
Few ideas I've got are. Gas valve not modulating, air pressure switch and or venturi or pump?
Thanks

 

[Billy Bob Bob]

try taking the filter out of the return and cleaning it,take the heating thermistors resistance should be 11k at 25 degrees ,remove the plate heat exchanger and clean it,check gas pressures

air pressure switch and or venturi or pump? not the issues

 

[marleyco]

Thanks gas man, I'll try as you suggest.