Baxi Solo not igniting burner properly

[Major Lee]

I have a Baxi Solo 3 60 PF (41-075-07). It has been working fine for a few years now, but has recently started playing up.

What I think is happening is as follows:

First thing in the morning HW and CH come on together all works OK.
At some stage both turn off normally(everything up to temperature).
The CH won't come back on when room temp drops - all the lights come on boiler, fan and pilot, BUT Burner and its light don't.
(I think it does the same the other way round too but harder to tell, i.e. if CH is up to temp then it doesn't heat HW)

If I manually turn off HW from the control panel, then the CH kicks in and I can then also turn HW back on and it works again.

I am guessing I either have a duff timer, or the boiler is getting confused by thinking that when CH is up to temp it doesn't need to heat the HW and vice versa.

Any help greatly appreciated.

Oh forgot to add, pump and motorised valve are working fine.

 

[Malc C]

I had something similar happen, and then shortly after the boiler would not ignight at all. Turned out to be a faulty gas valve. This was replaced and the boiler has been fine since - Cost was around £120 fitted if I remember correctly

 

[gas4you]

The boiler is not clever enough to know if it is being asked to heat HW or CH.

It just gets a signal to fire up.

IF all the lights are on as you say then yes it could be an intermittent sticking gas valve, but you need to confirm that the pilot is alight first and that the pcb is receiving the signal to say it is alight as without this it will not tell the gas valve to open.

Could just be partially blocked pilot injector, loose connection etc etc, but all of these are Corgi territory.

 

[Major Lee]

Yes, the pilot light is lit and the fan is on.

I can get the valve checked, but if it was sticky, I am not sure why it would start working as soon as I turn the HW off and then the CH back on again?

 

[gas4you]

When it won't fire try tapping the gas valve with a screwdriver.

 

[Major Lee]

Thanks will do - just taking it apart now


Bah - always the same with intermittent faults. It won't do it while I am watching!

Left it running, I'll post back with the results later.

Thanks for the pointers so far

 

[weareleeds]

After pilot lights does it carry on sparking? If so there is a kit to change electrode & pilot assy or could be a duff pcb

 

[Major Lee]

thanks, but no, it does recognise that the pilot light is lit

 

[Soggy_weetabix]

Gas Valve.

Try whacking it with a pair of grips

Dave

 

[Major Lee]

OK managed to get it to go wrong again. Tried whacking - firmly but didn't want to break anything!! Didn't work.

However, as usual, just turning it off and on at the timer and it springs back in to life.

Also this time the HW wasn't on - so this is exactly what happened:

This morning heating came on stopped at temp on thermostat
Wife got cold! Turned thermostat up heating came on, off again when up to temp
Just now, heating clicked in cos below temp in thermostat.
3 of 4 lights come on boiler, fan and pilot but burner wont light
Whacked! no change
Turn CH off and on at timer, springs in to life

 

[Terrywookfit]

Have you got voltage at the valve main solenoid??

If not try tapping PCB you could have a dodgy relay !!

 

[Major Lee]

OK - seem to have got to the bottom of it all.

Just noticed now that whilst it was working, the burner and pilot were clicking in and out. So hats off to all those people who said gas valve. I would say I have a valve or pressure problem. When I turn the control knob down it seems more stable.

Thanks for all the prompt help - at least I know what needs doing now, makes me feel happier when I get someone round.