Worcester Bosch 24i/28 junior about 15 years old.

[floopypep]

Had a problem during the winter with the flow turbine sensor freezing and water leak.
Replaced the flow sensor the boiler now starts to fire up with out dhw or ch being called for.
After it lights the reset flashes fast. i replaced the pcb with a recondition one but the fault is the same.
I have checked all the sensors and they appear ok.

Has anyone come across this before or could anyone offer a solution.

 

[UNG]

Have you checked the troubleshooting guide in the servicing manual https://www.worcester-bosch.co.uk/professional/support/literature/search?q=24i+junior
I usually find the flow charts in the manual very helpful when trying to locate / identify faults faults

 

[floopypep]

Hi yes but nothing appears to cover this problem, thank you for your reply.

 

[Geoff1946]

You do realise that it does occasional runs of a few seconds deliberately ?
Can't recall exactly why but the WD repair man did tell me when I queried it a few years ago.

 

[floopypep]

You do realise that it does occasional runs of a few seconds deliberately ?
Can't recall exactly why but the WD repair man did tell me when I queried it a few years ago.

This is lighting and continually running. Thanks for your suggestion.

 

[michael8554]

1. Try different modes on the programmer.

2. Next set the programmer to CONSTANT.
Does it still fire up with the HW and CH thermostats disconnected ?

 

[floopypep]

Sorry but no programmer on this model and no external thermostat.
Thanks for your input.

 

[Steviesparkie]

Sorry but no programmer on this model and no external thermostat.
Thanks for your input.

Did you swap the old microchip when you replaced the pcb ?(into the new board)

 

[floopypep]

The boards come complete there is no swappable parts.
Thank you

 

[floopypep]

This is original manual.

 

[UNG]

Had a problem during the winter with the flow turbine sensor freezing and water leak.
Replaced the flow sensor the boiler now starts to fire up with out dhw or ch being called for.
After it lights the reset flashes fast. i replaced the pcb with a recondition one but the fault is the same.
I have checked all the sensors and they appear ok.

Has anyone come across this before or could anyone offer a solution.

This is a condensing boiler so will run on initial start up to fill the syphon with condensate once this is satisfied then it will resume normal operation

You do realise that it does occasional runs of a few seconds deliberately ?
Can't recall exactly why but the WD repair man did tell me when I queried it a few years ago.

Worcester boilers have a pump anti seize function that runs the pump for a few seconds after it has been idle for 24 hours

 

[floopypep]

The boiler lights and runs continually with the boiler stat in off position.
It runs till turned off.

 

[michael8554]

From the Troubleshooting Guide that UNG pointed you to:

Burner on with no demand - Autofroststat. Board fault. - Test G

Carry out Test G

 

[Andy1733]

Is the boiler running on heating mode. IE are the rads getting hot?

 

[floopypep]

From the Troubleshooting Guide that UNG pointed you to:

Burner on with no demand - Autofroststat. Board fault. - Test G

Carry out Test G

Yes done that i suspect the recon board is faulty sending it back and have ordered another one.
Thank you.

Is the boiler running on heating mode. IE are the rads getting hot?

Yes the radiators are getting hot am changing the pcb suspect autofroststat.