Engineer has replaced PCB, thermistors, stepper motor and boiler still fails - reset light and mains power indicator light both flash + pump switches on when there is no call for heat. Problem does not occur when eco button is activated. Engineer is stuck - says there's nothing more he can do and new boiler is only answer. Surely not?

Tom H4BC, July 2016

There are quite a few models of the Junior 28i spanning a good number of years. So assuming you haven't paid for any parts as your engineer hasn't repaired your boiler you can pay a fixed fee to Worcester & they will replace a number of parts depending on the fee you pay, there are 2 or 3 pay scales I think, definitely cheaper than a new boiler & if it can't be fixed, i.e. it's obsolete they'll tell you. Plus within the price you pay you'll practically get a refit. However, if you get your "engineer" to call Worcester tech & explain what's happening they will advise him, providing he's gas safe registered & competent then he should understand. But it sounds like he's been dibbing in the bran tub to me.

An Engineer, August 2016

"Problem does not occur when eco button is activated"

So how does the Eco button change the way the boiler works?

From the manual:

3.1.5 DOMESTIC HOT WATER PRE-HEAT
The hot water heat exchanger is kept “pre-heated” to reduce the time taken to deliver hot water at the tap. Pre-heat is enabled by default, during the initial boiler start up and the ECO button is not illuminated.
Eco mode is an energy saving function allowing hot water to be heated only as and when required, by running a hot tap, this is OFF by default.

So, in Eco mode the boiler won't try to pre-heat. (which suggests it won't run the pump unless there is demand.

Further on in the manual:

3.1.6 BOILER RESET
In the event of a fault, the reset button will flash once per second and the blue mains indicator light will flash.
1. To reset the boiler press the reset button for approximately five seconds.
When the boiler resets the reset button will no longer be illuminated.
2. The mains indicator will no longer be flashing.

If the fault remains and cannot be cleared by pressing the reset button, contact Worcester, Bosch Group for
assistance.

Worcester Bosch have a helpline 0330 123 3366

These MAY help more:

https://www.youtube.com/watch?v=_wpgiBzASvI

http://www.mrboilerrepairs.co.uk/fault-codes/worcester-bosch-boiler-fault-codes/fault-codes-worcester-greenstar-24i-28i/

XXX, July 2016

So the service engineer has been guessing and he's probably correct when he says that there's nothing more that HE can do - his diagnostic skills are not good enough and sadly you pay for his lack of skill in time and materials.

Worcester Bosch have a helpline 0330 123 3366

Good Luck..., July 2016