Central heating not working on Timer mode

[nobackwheel]

Hi
I seem to have an issue with the timer on my central heating system.

We moved into new house a few weeks ago, I checked the boiler, and checked the heating/hot water - all seemed fine.

Some of the upstairs rads were a little cool, so bled them - lots of air - all seemed fine.

Until yesterday - The hot water works 100% - either manually turning it on, or from the timer.

The central heating however, will not turn itself on from the timer - I can do it manually (like i did at 5:50 this morning!) but from the timer it;

Fires the pilot light
Makes a few quite loud (loud enough to wake me up) banging noises
Goes back into standby
Repeats every 5 minutes or so

I'm presuming therefore that it's an issue with the Timer?? Any ideas

Please help - I don't want to have to wake up early again

It's a Suprima L boiler. Timer is an electronic one - not sure of the model

Thanks

 

[nobackwheel]

an update

left the CH on all night - dropped the temp to 16 so it wouldn't be too hot/cold

problem - woke up - felt cold - rads not warm

Checked boiler - it had locked out, pressed reset, CH back on again

Still the same with the timer obviously

What's going on?

 

[bengasman]

It would help if you let us know what timer you have.

 

[nobackwheel]

It's a drayton tempus seven

can't see any model numbers

Hope this helps

thanks

 

[bengasman]

first guess is that your ch valve doesn't open, or blockage/airlock in the heating pipework.

 

[nobackwheel]

would that stop the CH working completely?

how can I check for airblocks in the pipework?

 

[bengasman]

Airlock. I normally listen to the sound, and try to find obvious places to bleed, but would have a hard time explaining how you do that over the net.

 

[nobackwheel]

airlocks in the pipes - how do you bleed those?

would that be on the FAQ?

i've bled the Rads.

Why would an airlock stop the boiler coming on during 'auto', but not during 'constant'?