Follow the steps:
1. Is fan working (it is normally the first 'noise' when it first switches on)?
2. If 'yes', Does the solenoid valve click on? (second noisy 'click' after fan has been running a few seconds)
3. If yes, Can you hear the 'ticking' of the ignition unit? (on the Mk1 Neataheat [guess this might be yours?] the ignition unit stays on, and 'ticks' (sparks) continuosly while boiler is firing).
4. If yes, Does the pilot flame ignite? (look thro the little glass spyhole for a single small blue flame).
5. If yes, and the boiler doesn't fire up, it is likely to be the dreaded 'gas valve' - as alluded to in the last post. Its official description is Mercury Vapour valve - Potterton part no 404451. Officially now obsolete, if your lucky to find a supplier with one, it will cost anything up to £300. But search locally and you might get it for around £100.
If answers to Q1 thro 4 are 'No' you will have to problem solve each stage yourself eg if Q1 the fan's not coming on, it might even be a simple blown fuse.
Algynon, February 2009
