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Plumberpro
Plumberpro, Home Appliance Technician
Category: Appliance
Satisfied Customers: 634
Experience:  Heating and hot water heating appliances experienced
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My sabre 24 boiler cuts out occasionally after the start up

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my sabre 24 boiler cuts out occasionally after the start up cycle. have a flame then it cuts out. reset it and after 1 or 2 tries will work again.
Hi , could be a faulty fan or air pressure switch . sometimes when the fans start to fail ,its not all at once but agradual process .you could check this with an electrical tester on the APS when the boiler is switched on
Customer: replied 2 years ago.

is the air pressure switch the same as the pressure differential switch.

Hi , yes,check for continuity through it as the fans running .however with intermittent faults it could be a few issues.
If the boiler is overheating or reaching temperature it could be the the temp ntc/ stat..
Do you get heat?does it run hot water nd heating for a while and then cutout? How long? Thanks ,sorry for all the questions but but it helps narrow things down
Customer: replied 2 years ago.

boiler goes through the start cycle and when it seems ready to open the main gas valve it cuts out.

Hi , when you say it goes through the start cycle, does the fan and pump run,can you hear the boiler sparking?
Customer: replied 2 years ago.

pump and fan both run and I can see a flame through the inspection window

Hi ,thanks for that . from what you describe it seems that the boiler is overheating due to a faulty (primary)thermistor/ temp stat, locking out on overheat.change the the central heating stat.however vif you are changing that one , it would be best to change the hot water come too. Relatively cheap, around 20 pounds each and fairly easy to change

Customer: replied 2 years ago.

the boiler lies idle from 11-00 to 6.am. it cuts out at the first attempt so it does not have time to heat up .

Hi , originally ,in your first chat ,you said it happens occasionally. Has this changed as you are now saying that it cuts out at the first attempt
Customer: replied 2 years ago.

what happens is you can go for a shower in the morning then 30 mins. later the boiler will not fire up for 2nd. shower. the ch. if you try to switch it on in the afternoon for eg. it can take 4 or 5 resets to get it going.

OK , sounds like it locking out on overheat. Are there any fault codes, ie flashing lights?
Customer: replied 2 years ago.

no fault codes, indicator light is normally green but turns to solid red when the fault happens.

Hi Does the boiler do the same for heating!? And does the hot water ever go hot , then cold,hot then cold?

Customer: replied 2 years ago.

yes same for heating, hot water once it goes hot it stays hot.

OK,we did go round the houses a bit but the only answer/ explanation I can give is that it is overheating, so replace the two ntc temperature sensors . as the fact it runs for a while indicates the pump etc is OK , so it must me getting too hot and cutting out on the overheat stat.

Customer: replied 2 years ago.

but why does it cut out first thing in the morning `when the boiler has been off all night and is cold.

The boiler is designed to heat up very quickly . for example ,if you pump was broke and you put the heating on , the boiler would cut out in about 4 seconds.
Unless there is a PCB fault , the boiler seems to be locking out on overheat. Overheat occurs due to a pump or stat issue
But I do listen to my customers when I'm out on a job as they have lived with the problem longer than me ,I've given you my answer , what's your gut instincts?
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