Thanks for the suggestions Gents. Dave, your link doesn't appear to work, please could you send again?
cjb1971 - Good point about the DC, will check again :oops:
Any other ideas?
The burner on my 14/19 ignites when there is a demand from system, but then goes out within 2->3 secs. The start sequence appears to be correct (fan runs for 20 secs before igniter lights gas, process is repeated 4 times before lockout light comes on) I have already replaced the flame sense...