Baxi Solo 3 50 PF intermittent burner.

[metalsteve]

I have a problem with my Baxi solo 3 50 PF.

In the initial instance when the CH or HW demands heat the boiler on indicator will come on, followed by fan indicator, fan starts, then pilot ignites, pilot indicator on followed by burner and burner indicator.

It will run like this for 5-10 minutes and then the burner and burner indicator will go out, the fan will continue to run for a few minutes and the pilot igniter can be heard clicking, fan will then stop and fan and pilot indcator will go out. boiler on light still illuminated.

Once this happens the boiler will not fire up again unless left off for some period of time. the water temp in the rads or the tank is just luke warm and the fault occurs weather i am wanting CH, HW or both

I have changed the PCB which did not cure the fault and also checked the boiler stat thermistor (reading 900k ohms at room temp) resistance decreases with heat.

I've included 2 pictures, first of which shows boiler indicators when first fired up, second shows lights when burner has gone out.

any ideas as to what may cause this?

Untitled

• metalsteve
• 31 Oct 2011
• 1

Untitled

• metalsteve
• 31 Oct 2011
• 1

 

[45yearsagasman]

This could possibly be a fault with one of the solenoids on the gas valve going open circuit during firing.
Not easy to diagnose as readings have to be taken during the fault condition and I would advise against trying to diy.

 

[nickso]

When it is not working try moving/tapping the thermistor. (right side,red plastic,two wires attached to it). A rare fault on this turd is a dodgy thermistor/connection. It gives similar symptoms to the ones you describe.

 

[Agile]

Surely if it was a thermistor fault then he would not hear it sparking/trying to light?

I would expect a gas/combustion fault which is not for DIY repairs.

Tony

 

[metalsteve]

Thanks all for the replys.

I'm sure the thermistor is ok, the contacts are clean and the connectors tight and it measures ok.

so possibly gas valve solenoid. I've read on other posts about a faulty APS causing similar symptoms. Is this a common fault.

I'm an electronics tech by trade so i'm happy to safely test voltages or resistance, rest assured i will not go any deeper than that and will not touch anything else.

I had one engineer out who thought it was the pcb but is now a bit stumped as he's not seen the fault on this boiler before.

Now considering contacting baxi heat team to arrange one of thier engineers to come out.

 

[Agile]

A reasonable local in dependent is likely to be cheaper than a Baxi eng.

These are very simple boilers and it should be easy to identify at the point when the problem occurs.

The trouble is that an intermittent fault does not occur in front of an engineer.

We dont advise on anything connected with the APS but I dont see thats likely to be your problem because the boiler is clearly enabled up to the point of lighting the pilot.

The engineer you had to visit, on what basis did he come? Was he not paid because he could not identify the problem? Or was he paid even though he could not identify the fault?

Tony

 

[phildj]

Just had exact same fault repaired it was the gas solenoid. Baxi help line told my fitter that symptoms can be misleading but is common fault.

 

[knightstyle]

I have exactly the same fault, followed the fault chart which said faulty PCB. Replaced PCB and no change!
So what can it be? All boiler on lights are normal, fan running, checked flow switch, fan air pressure switch, overheat thermister, all OK. The main burner solenoid is about 1.5k ohms so that seems OK. But there is no voltage on it! should there be?
Any ideas?

 

[ianmcd]

This post is 6 years old you would be better starting a fresh post

 

[Agile]

Even with a new thread I would be reluctant to give advice on a fault which is likely to need an RGI to repair.

 

[dilalio]

Even with a new thread I would be reluctant to give advice on a fault which is likely to need an RGI to repair.

Hey Tony... Welcome back