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I have a baxi combi boiler(105e) rads were just luke warm bit i still had hot water got british gas out fitted new pcb+sensor still no better then they said neded power flushed(£600) friend who is a plumber took rads off and cleaned them out with hosepipe now the boiler fires up then pilot light goes out but fires up ok for hot water any suggestions what to try next.

The baxi 105e does not have a pilot light. So it's either not a Baxi 105e or you mean the flame LED on the control panel.

Check all isolation valves under the boiler are fully open

Is the pump running ok ?
do any lights flash on the boiler ?
boiler pressure set between 1.0 and 1.5 bar ?

When your friends removed the radiator -what was the water like ? much sludge ?

Get a heating engineer out to take a look. Don't go for a powerflush just because BG say you need one. It's a easy job and quite abit of money, I'm not saying all - but that's the reason some 'heating engineers' push for system flushes.

You're lucky your boiler isn't that old - a few years older and BG would have pushed to sell you a new boiler.

Possibly the pump cannot circulate hot water because of air in the system. Bleed pump and rads. If this does not work, please describe in more detail your ch starting sequence and where it stops working eg room thermostat turned up, then boiler fires, then pump starts etc.
Powerflush will not shift much more than what your plumber already done with a hosepipe, so avoid a powerflush.

The british gas engineer said the pump was ok doesn't seem to be any air in rads when trying to bleed them. When you turn from hot water to hot water and c/h the boiler tries to fire up but swithes off and the flame light neon flashes red.

maybe ask for a second opinion on the powerflush but true enough removing the radiators will not clear a choke in the pipes leading to them Then again a powerflush would not remove a choke that bad anyway so check that any quotes include physically removing blockages as required

It's a fault with the minimum rate gas pressure setting, the flame sensing electrode/lead if all these are ok - it can only be the PCB.

Had someone else out to take a look he thinks it might be diverter valve does onyone else agree this could be the problem

BG ALWAYS try to sell you a power flush. Treat such a recommendadtion with caution and 600 is waaayyyy over the top anyhow. With all due respect to htg engineer it MAY not be the PCB. As the boiler lockout seems to occur on the CH side rather than DHW it could be that your room stat is incorrectly wired.

In general terms:

a If the lockout condition occurs within seconds or applying power or pressing the reset button with no call for heat then it's wiring.

b If it occurs when a call for heat is made then again it's wiring.

c If it occurs during the ignition stage then you need to fault find the igniton sequence.

d If it occurs during the heating process then that points to the overheat stat on the boiler.

If DHW works but CH doesn't then I suspect the wiring frankly. The clue for me in that direction is in your post of Jan 02 at 7.56pm. I'd advise to check the wiring BEFORE contemplating fitting another new PCB.

Hope that helps.

Cheers

Have the gas pressures been checked ?

Get the minimum rate gas pressure checked. By a CORGI registered installer

Let us know if you got this problem sorted. What the problem was etc.

Thanks

Thanks for your reply will let u know what happens next

Waiting for heating engineer to come and have another look at boiler. Now the boiler is firing up and going through the temp very quickly the feed pipe is very hot but the return pipe is cold you can feel vibration on return pipe. A couple of the radiator pipes get hot but no heat in radiators at all. I would be grateful if anybody as any advice on what is wrong now.

You're taking the word of the last heating engineer that the pump is ok - is it ?

have you checked all the valves under the boiler are turned on ?

all radiator valves turned on ?