Isar HE24 User Control not working

[Franco]

Hi

I have recently had a problem with my boiler not wanting to fire up. Had a plumber come in and it turned out to be the pump. Plumber replaced the pump, but after that the User control panel stopped working. The plumber said there was current going to the user control and that it must therefore be faulty, and that if I wanted to replace it myself it was easy enough to do.

The boiler did seem to be working. CH is fine, and hot water is working, with the only downside being that I can't regulate the HW temperature.

I have tried to replace the user control and the new one doesn't work either, from reading a few forums the general information seems to point to a faulty main PCB.
These are quite pricey to replace, and so I want to make sure that it is indeed this that would need replacing. There is a fuse on the PCB which can sometimes go? Is it worth checking this?

Also, I am thinking that if it's working I can put up with not being able to regulate the HW temp (it comes out at maximum temp). The only thing that concerns me is wether there are other functions that could be affected by the PCB that I'm not seeing. I've got CH and HW, but is it safe? Does the PCB control any safety cutouts or anything like that.

All advice is welcome

Thanks

Frank

 

[fixter1]

check your fuse mate,

 

[Franco]

I've checked the fuse, seems to be intact (I'm guessing it would be pretty obvious if it was blown).
My main concern is whether it is safe to keep operating the boiler if there is a fault on the pcb. on the surface everything seems to run fine apart from the user control.

 

[kirkgas]

if you are competant to do this repair(your decision) what to try next is do away with the purple wiring harness that goes from the back of the user control to the PCB, remove the user control and plug it straight onto the pcb, you might need to tip the pcb forward a bit for access turn on the power and see if it works, it is possible that the wiring loom is goosed, (£10) it is possible to leave it like that till you buy a new harness as long as you are sure nobody will poke about it, if it doesnt work it could be the control user housing (£23)(where the purple loom plugs onto), if not that it will be the pcb

 

[Franco]

I've tried replacing the user control (along with the housing and loom), so it looks like the problem is with the PCB. Does anyone know if it's ok to carry on operating with faulty PCB? At face value it looks like I've only lost the ability to control the HW temperature.