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vaillant vcw-gb 242 eh not igniting to either heat dhw or ch?

boiler was drained to look at water valve diaphragm as central heating was not working (ie) diverter valve not being pulled into CH microswitch. Refilled to 1.1 bar and started, pump and fan runs but does not pull into CH position when switch operated for this nor does it ignite the boiler for DHW, When the microswitch for CH is operated manually the boiler locks out after a few seconds. The servo valve appears to work ok as do the microswitches. Can anybody HELP

keith
April 2007

Vaillant Heating, Home Heating Systems Heat Ch Boiler

I HAVE THE SAME MODEL BOILER. SAME PROBLEM AND WHEN THE ENGINEER CALL HE FOUND THE FAN WAS TURNING BUT WAS NOT CREATING ENOUGH AIR FLOW PRESSURE FOR THE FUMES TO BE EXTRACTED ANS THERE FOR NO IGNATION. REPLACING THE FAN HAS SORTED THE PROBLEM. THE BOILER IS PRODUCING CH AND HOT WATER OUT OF THE TAPS.
I HAVE ALSO REPLACED THE WATER

MANOJ PATEL
February 2010

either the boiler is airlocked, or the servo-valve tubes are blocked. if the boiler goes to lockout when you manually operate the microswitch then it is more likely to be airlocked.
it should not be able to bring the fan on until the hydraulic divertor valve has moved into heating or hot water position...
It won't fire up even when you operate the switch manually b
ecause the gas supply is hydraulically failsafed. you will have to bleed the main heat exchanger inside the combustion chamber. only try this if you are corgi registered. up to now you have been dealing with water. beyond this you are in gas regulation territory and contrary to common belief D.I.Y GAS DOES NOT EXIST...please be very careful.

T.H.S
April 2007