HELP: Baxi combo instant 105e - No Hot Water Or Heating

[Marshk]

Just woke up to find the boiler is not switching on when heating or hot water demand is made. I tried power on/off the boiler and checked water pressure is at 1.5.
No signs leading up to this fault.

Strange thing is no flashing LED diags are being displayed.

Any ideas what is going on ? Hoping it’s not a big PCB error and something simple like the heating thermistor.

If someone can point me in the right direction that would be really appreciated.

 

[Alec_t]

Fuse intact?
Any display at all?
Any sound from fan or pump?

 

[Marshk]

Fuse intact as power LED comes on. Unless you referring to fuse on pcb whock I haven’t checked
Other than power LED and analogue pressure dial pointing 1.5 no other display including flashing LEDs.

No sound from pump on switching on power to boiler or when demand from hot water or heating.

 

[terryplumb]

Check the fuse on the boilers main terminal block ,where the mains power supply connects. There is a 2 amp quick blow fuse attached to the end of the terminal block.
If that's blown ,the question is what's caused it to blow ,and you will likely need an engineer to investigate.

 

[Marshk]

Thanks for pointing out where to look
For fuse - it’s in tact.

Guessing it’s pointing towards PCB swap

 

[terryplumb]

Sounds like it.

 

[Madrab]

I would be doing few more input/output checks first before condemning the PCB, if you aren't getting any flashing errors. Do the demand LED's light up when running HW or calling for CH? External controls or internal clock?

Run through the troubleshooting guide and do some voltage checks if you are able, otherwise get someone in to troubleshoot.

 

[CBW]

Turn the boiler off, do you get any noises? Have you tried the hot water only selector on the switch? Have you tested for correct voltages present?

 

[Marshk]

I would be doing few more input/output checks first before condemning the PCB, if you aren't getting any flashing errors. Do the demand LED's light up when running HW or calling for CH? External controls or internal clock?

Run through the troubleshooting guide and do some voltage checks if you are able, otherwise get someone in to troubleshoot.

Turn the boiler off, do you get any noises? Have you tried the hot water only selector on the switch? Have you tested for correct voltages present?

Only power LED comes on and no others whether i hot water or heating demand.

No boiler sound sound on turning boiler on/off or on Heating/Water demand.

Selected only water as well as water/heating with no difference.

The heating is controlled by external timer thermostat.

Not tested voltages

Engineer available early as tomorrow but hoping to diagnose the problem forehand and order part to save another day of no heating with kids at home.

I’m fairly experienced & comfortable with electronics so should be able to swap out pcb if that is all that’s required.

 

[Marshk]

The manual troubleshooting takes me to section B which points to Pump or PCB.

Would I be correct to think that it can’t be pump just by the fact that I’m not seeing any of the diagnostics lights come up ?

Boiler seems dead other than the power LED being green.

 

[terryplumb]

Have you checked for 230 Volts at the PCB terminals quoted in the trouble shooting guide ??

 

[CBW]

The manual troubleshooting takes me to section B which points to Pump or PCB.

Really, I get section L first.

 

[Madrab]

Really, I get section L first.

Maybe I'm looking at the wrong manual troubleshooter but the one I'm looking at for the 105E only goes up to 'K'??

@Marshk you need to test for voltage on the PCB as @terryplumb suggests otherwise you may be buying a PCB for nothing.

 

[CBW]

Maybe I'm looking at the wrong manual troubleshooter but the one I'm looking at for the 105E only goes up to 'K'??.

Unless OP is wrong, it’s an instant? So I looked in the manual I have for that, which goes up to M, oddly, the issue could be M as well, but mentioned no output from boiler other than led for power on

 

[Madrab]

Oh right, that'll teach me to read the title properly lol