Can anyone help? I had a strange fault on my combi, which is 10 years old and has been quite reliable, only having to fit an external expansion chamber last year. When the boiler is switched on the CH runs all the time despite the clock timer being in the off position and the control knob being on the "summer" setting of hot water only. I have fitted a new DV ans the plunger does actuate the micro switch when we use hot water. So I now have to turn the boiler off in order to stop the CH and turn it back on again if we need hot water or CH,, any ideas?????
Ariston eurocombi mffi a23, CH on all time
- Thread starter dommo
- Start date
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Is there a room thermostat in the house and if so does the boiler take any notice of that?
I'm wondering if the internal clock/timer connector has been dislodged from the main circuit board. That could possibly leave the heating controlled only by the wire link (where a room thermostat would normally be connected) which might leave the heating on full time.
The installation manual is here
http://www.ariston.co.uk/uploads/doc47be9cb6d285b.pdf
See section 2.10
The installation manual is here
http://www.ariston.co.uk/uploads/doc47be9cb6d285b.pdf
See section 2.10
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On this boiler they're is a main sensor, which i know on other models, can slip the boiler into frost mode, causing the heating to come on and off as it pleases, without a demand. Sensor's are usually very cheap and easy to replace.
May not be the same case here as i said on "other models", but a cheap solution to try first.
May not be the same case here as i said on "other models", but a cheap solution to try first.
Yes measure the "resistance". Aren't you going to advise dommo what the resistance should be, at certain temperatures the boiler reaches, to let him know if he is receiving correct readings?
guys i'm a motor vehicle technician for 30 years and I found the advice very helpful. I did check what temp sensors I could and they are functioning ok, there is no frost protection sensor fitted to it so i am still a bit stuck,
dommo slow it down for us please, take a step back. We haven't got any further thus far.
As best you can describe the fault from a fresh.
Forget what you have already written take time on this next post. The better you describe the fault the easier it is for people to understand whats going on, alarm bells ring when you mention certain things. thanks.
As best you can describe the fault from a fresh.
Forget what you have already written take time on this next post. The better you describe the fault the easier it is for people to understand whats going on, alarm bells ring when you mention certain things. thanks.
Op can you slow down a little and give us clear answers to a few questions please.
Did this continual CH start just when you changed the diverter valve?
Does the diverter valve pin retract?
Did you change the microswitches or just refit the old ones?
What was the cold resistance of the sensors?
Four questions = four answers!
Tony
Did this continual CH start just when you changed the diverter valve?
Does the diverter valve pin retract?
Did you change the microswitches or just refit the old ones?
What was the cold resistance of the sensors?
Four questions = four answers!
Tony
ok guys here goes. About 11 months ago boiler expansion vessel diaphram was leaking and i was led to believe it was a very difficult job to do, so a corgi guy fitted an external vessel next to boiler. Since about the time i was getting the vessel replaced the CH just kept on all day and the electronic timer on the facia had no control over it. The only way I could stop the CH from working was to turn the boiler off electrically. I persevered through last winter by manually turning boiler on and off for heating (which was a real pain on cold mornings as the house was cold) and also having to turn boiler on/off when we needed DHW. In summer it was bad because the kids would turn the boiler on for a shower then forget to turn it off, when i got home from work the house would be boiling hot!! So i replaced a complete diverter valve last week but the fault is still there. 1. The summer /winter knob has no effect on operation, 2.The overheat temp sensor reads zero resistence when disconnected , bot if you do disconnect it when the boiler is on then it cuts the boiler out so you have to reset it. 3. The temp sensor on diverter valve reads 18k cold 4.5 k hot. 4. When the boiler is on and thus the CH is on, then if you open a hot water tap the plunger comes out and operates the micro switch.
Hope this helps
Hope this helps
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