Boiler Blues

[IamFreezin]

I have a Vaillant GB 221 H Combi-Boiler and have the following problem with my central heating.
Although the pump works when heating is turned on, boiler refuses to ignite.
If boiler does ignite it cuts off after a spell of time (generally between 3 minutes to 10 minutes). Then temperature gauge drops until it reaches the Zero mark. After this, boiler will not ignite again to reheat and circulate the hot water within the system.
I have no problem with the hot water as boiler ignites every time I turn the hot taps on.

Any advice or tips to help sort my boiler blues will be most Welcome.

Yours in Hope
IamFreezin

 

[Bahco]

Then temperature gauge drops until it reaches the Zero mark. IamFreezin

Is this gauge you are looking at the pressure gauge.
If so you need to refill the system to approx 1 bar.
Try it and report back

 

[kevplumb]

check the servo valve is closing properly

try

//www.diynot.com/forums/viewtopic.php?t=20317&postdays=0&postorder=asc&start=0

 

[IamFreezin]

Thanks for the feedback. Answers as follows:

The gauge is the temperature gauge and not the pressure gauge

The servo valve is working properly

 

[Bahco]

Thats me finished then

 

[kevplumb]

try gently pushing the black cam on the servo valve down the spring aint strong enough if the pin has lime on it

spesh when in heating mode

 

[IamFreezin]

Changed main circuit board and thermostatic valve on main heat exchanger. All working well now.8) Fingers crossed! it will stay that way. Thanks for the feedback. Much appreciated