Baxi 105he combi 80degrees flashing.

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Hi all. I have a problem with a baxi 105he combi boiler. When I turn on the Ch boiler fires up and shows 30degrees light. Then after a few seconds everything cuts out and 80 degrees light starts to flash. The boiler restarts after a few seconds and fires up again the then the same problem. Does anyone know what the problem is. Thanks in advance for any help.
 
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It sounds like a circulation issue

All rad valves open, TRV pins not stuck down ?

I would then be looking at the pump
 
Hi. Thanks for the quickly reply. I forgot to mention that when I turn on the hot water the same thing happens. All the trvs and pins are ok. Pump seems to run but I don't know what it could be. :(
 
Could be a weak pump or a blockage. Better to get an engineer in to diagnose correctly rather than throw a part at it
 
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That's indicating a possible fault on one or more of the following:
Fan, Primary Thermistor, Flow micro switch assembly or PCB.

A Gas Safe Registered heating engineer will be able to easily pin point the fault, but more importantly is competent to ensure that your appliance is operating safely once the fault has been rectified.

James.
 
And make sure no-ones turned one of the heating isolating valves off by mistake ( had this a few times when someone thought they'd turned the filling loop off)
 
Thanks for all your replies. If the primary thermistor was at fault the hot water should be working ok? Shouldn't it? Thought the thermistor was in the ch flow pipe. ?
 
Sensor fault change it , it sits in a dry pocket so no need to drain it .

And yep the main (ch) stat will show a fault on hw to
 
I'm sure I have to drain the system down as its in the flow pipe. Also I just tested the thermistor and it read 14k ohms. Is that the right reading?
 
oh so you work on them all the time then, do you think i would tell you its in a dry pocket if it wasnt .
No point telling you if the reading is right or wrong as you wont believe me .

Its a 15 quid fix and 5 min job
 
The ohms reading will change dependent on temp anyway so we can only answer that if you tell us what temp its at
 
Thanks gas112. It's not that I don't believe you just thought it would be in a wet pocket. Anyways got the part from a heating shop and he said its in a wet pocket so I just drained the boiler and fitted the part. Refilled and its working fine. Thanks for everyone's help. Saved me a for fortune. :)
 
Thanks gas112. It's not that I don't believe you just thought it would be in a wet pocket. Anyways got the part from a heating shop and he said its in a wet pocket so I just drained the boiler and fitted the part. Refilled and its working fine. Thanks for everyone's help. Saved me a for fortune. :)

You obviously changed the dhw temp sensor as this sits in a wet pocket unlike the CH sensor that as 112 said sits in a dry pocket.

Had you not of drained down and flooded the boiler electrics then 112 would have been eliminated of any blame. :LOL:

You used heat paste on CH thermistor I take it???
 

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