Worcester highflow 400 bf driving me crazy

[Euxton]

Hi guys

Would appreciate some advice ofF anyone that may know what is causing my highflow 400 to just work for water. The other night the heating went off so I checked the pressure and noticed it had gone right down so I filled it up but since then then central heating has not worked.

The hot water works & and boiler kicks in when I turn the water stat on the boiler to the on position and up, however when we switch the heating stat up and turn the programmer and room stats on, the pump starts and demand light comes on, but the boiler doesn't fire.

We have changed the diverter valve as we had a similar issue a few years ago and it was the diverter valve then but at that time the burner used to kick in and go off after a short time.

I've bypassed the programmer and heating stat with no joy & now have hit a brick wall. Would appreciate any advice given. Thanks in advance. [/quote]

 

[Agile]

I think there may be a seperate thermister for central heating.

If thats the case then you need to check its resistance.

Tony

 

[Euxton]

Thnx for the reply Tony, do you mean the one with the knob attached to it or another separate one inside the boiler?

 

[Agile]

If you dont know what I am referring to then it may be better to call a boiler engineer.

Tony

 

[Euxton]

I have bypassed the thermister and the burner still doesn't ignite. I have checked voltage on both the heating control stat pins on the pcb and get nothing so im guessing the pcb has gone.

 

[boilerdoktor]

the 400 diverter valve works on hot water and then on demand energises the divertor solenoid.

Turn h/w demand off and c.h on. Is the solenoid on div valve magnetized??

If it is and no heating then the culprit will be the weep tube blocked between the div valve body and under the pump! Dont jump straight to the pcb on this.

 

[Euxton]

Thnx for the advice, got the boiler working. After removing the pcb due to not having any voltage on the heat stat pins, I noticed there was a dry joint on the back, which coincidently was one of the heat stat pins. Reworked the solder on this joint, put back together and bingo, boiler fired up straight away.

I also checked the weep tube yesterday when removing the diverter, thinking it was that but it was clear.

Thanks guys for the advice.