RAVENHEAT CSI85 DOES NOT SWITCH OFF!!

[dazz26]

hi
wondered if someone has come accross this issue before?
boiler is 10 years old and no real major issues till lately its been running without cutting out? until it boils like a kettle and th eoverheat kicks in and knocks it out, any ideas?

the only way i can switch it off is by the main power knob.

 

[nickso]

Check the thermistors first, faulty ones on ravenheaps throw up all sorts of weird faults.

 

[Slugbabydotcom]

Big suspect is the CH thermistor on the pipe to the right.
I'm suspecting it's the earlier wet sensor which will require the primary water draining from the boiler.
If perchance it is the later clip on type; these don't go wrong often, so it could be an issue of it losing direct contact with the pipe it is sensing.
In either case if you know how to use a multimeter you can pull the wires off and check the resistance expect readings in line with the chart below.

Big safety tip! If it is a wet sensor give it at least an hour after turning off and draining the water. I got a nasty scald once to bring you this valuable advice

If its not that you will need the services of a gas safe engineer and preferably one that specialises in repair.
Ring Ravenheat and they will recommend someone if you're stuck.