Baxi Duo Tec 40 HE Combi - No Hot Water Switching

[si_edgey]

Thank you so much for your help.

Got a 9 year old Baxi Duo Tec 40 here which has been functioning perfectly since we moved in a year ago. The boiler was recently relocated slightly higher on the wall during kitchen reno, around 3 months ago.

Yesterday my wife had a shower and all was fine, however since then the CH is working perfectly but there's no hot water.

Run a hot water tap and the boiler doesn't respond, no hot water light on the boiler, and no error codes.

Your thoughts are much appreciated!
Thanks, Simon

 

[cross thread]

Most likely the flow sensor on the water inlet

 

[Togo]

Could be your diverter valve has stuck in central heating position when it was disturbed. I take it you have a thermostatic shower & not an electric? Could be a faulty flow sensor. You're going to ask me how to now check aren't you? Dohhhhh!.....

 

[si_edgey]

Thanks for the responses - haha, actually I’ve tested the flow sensor now and it seems to be showing the correct resistance.

Given that the hot water flow isn’t registering at all, my thinking is to try replacing the PCB with a cheap refurb (£30) to see if that helps. Does that make sense?

 

[gas112]

So is the red light on inside the boiler constant or flickering or not at all

 

[ianmcd]

my thinking is to try replacing the PCB

Why do people always think it is the PCB, as @gas112 what is the neon on the inside doing when HW is running ? is it solid red, flickering or flashing

 

[si_edgey]

Thanks for the replies. As predicted, the PCB has the same issue. Did a bit more testing, the Hall Effect sensor has no red light. When holding a magnet to it, the red light comes on solid and the hot water heats as normal. What would the next step be?

Many thanks.

 

[RandomGrinch]

Thanks for the replies. As predicted, the PCB has the same issue. Did a bit more testing, the Hall Effect sensor has no red light. When holding a magnet to it, the red light comes on solid and the hot water heats as normal. What would the next step be?

Many thanks.

Hold the magnet there whenever your misses wants a shower?

Sorry!

However, if you were to search YouTube for say, "Baxi boilers a closer look at hall effect sensors" - there could be an interesting video with a view of a hall turbine and filter?

 

[DP]

Thanks for the replies. As predicted, the PCB has the same issue. Did a bit more testing, the Hall Effect sensor has no red light. When holding a magnet to it, the red light comes on solid and the hot water heats as normal. What would the next step be?

Many thanks.

Why is there ANY need to test further
You see no red light on the flow sensor when hot tap run
What issues does the pcb has and what is the PCB got to do with your fault

 

[si_edgey]

Hold the magnet there whenever your misses wants a shower?

I have literally done this.

However, if you were to search YouTube for say, "Baxi boilers a closer look at hall effect sensors" - there could be an interesting video with a view of a hall turbine and filter?

Thanks, that was helpful. So, if the sensor works but isn't coming on, does that mean the filter / turbine may be at fault?

This doesn't seem to be a replaceable part on the Duo Tec 40HE A, it seems to require a full hydraulic inlet assembly replacement?

Thanks again.

 

[RandomGrinch]

I have literally done this.

if the sensor works but isn't coming on, does that mean the filter / turbine may be at fault?

If the magnetic sensor bit works, that sorta suggests that the magnet bit isn't!

And as in the video, if there is a filter that can be cleaned, I would probably consider cleaning it!

I'm afraid I don't know if the part is replaceable or not; but there are parts that claim to fit the Duo Tec 40HE, for instance:

https://www.tradeboilerparts.co.uk/...CH-DUOTEC-24-28-33-40-HE-FITS-TO-PART-5114710