What does fault code F23 mean

Guff, December 2009

water level is low
have a look at the pressure gauge.
fill it up you should be ok.

VAILANT HEAD OF ENGINEER, January 2012

fault code 23 is probably caused by blockage of 4-5 inch rubber return pipe to primary heat exchanger which you have to cut off and refit using jubilee clips. Main sympton : fluctuating hot/cold water. Check this link : http://www.ukplumbersforums.co.uk/central-heating-forum/6979-vaillant-ecomax-622-2e-fault-f-23-a.html - hope this helps - solved mine.

squidgy, December 2010

Just Typing out of my book.
F.23 Water level low/Temperature range too wide.

Cause:
Air in appliance, system pressure too low,flow and backflow NTC reversed.
Pump obstructed pump running at lower capacity.

Hope this helps :)
P.s. you really need to find 835/2e book.

Laiyos, April 2010

According to my manual fault code F23 means 'water level low' but also listed is 'temperature rises too fast'. Causes - Pump obstructed, pump running at lower capacity, air in appliance, system pressure too low, flow and backflow NTC reversed

JB, January 2010