I also had a Heatline S30 boiler with this same intermittent fault.
I switch the boiler on and it will ignite and pump water to the rads but after 5-10 mins the gas will cut out, the boiler then tries to ignite again it sparks but does not ignite. It tries to ingite a few times and then the "check burner ionisation probe" LED flashes. If you switch it off and on again it will work as before for 5-10 mins.
I employed a Corgi (now Gas Safe) registered plumber who immediately concluded it was the gas valve. This was duly replaced but the same fault occured immediately.
We were given a choice of beginning to swap more parts, wiring loom, PCB, electrodes but with no guarantee of success or fitting a new boiler at a cost of £2000.
We have subsequently been getting various quotes and advice. As the boiler had effectively been written off I decided to have a look at the internals myself. I flipped down the control panel and opened it up to check the wires from the ionisation probe. All the wires, and chipsets looked ok, so I flipped over the PCB to inspect the solder joints. Whilst nothing looked too obvious there were a couple of dry joints. I resoldered these joints (one was to the back of the ionisation probe plug!) and closed the control panel. SUCCESS! the boiler now seems to be working perfectly fine but I will keeping a close eye on it for the next month or so.
After reading a number of forums this seems to be a very common fault with the Heatline S24 / S30. A number of other people have also identified this as a wiring issue - so my advice is check this first and save yourself a small fortune!!
John-Boy, April 2009
