baxi 105e temperature sensor fault

30 Jan 2006
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United Kingdom
can anyone help me, :confused: i have a baxi 105e that has recently started playing up, the temperature sensor neon is flashing, and the boiler keeps trying to fire up fully, it does so for only a few second before stopping. i still have intermittent hot water and my rads are warm but not their usual very hot. :cry: would i be right in thinking its the thermocouple causing this problem? any help gratefully recieved

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All of the 105E boilers that I have ever seen did not have a thermocouple!

Perhaps you have a special one off boiler?

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....but the 105 has separate CH and HW temperature sensors.....

It is the "70" or the "80" light flashing, or both?

You could measure the sensor(s), 11k ohms cold increasing on temp rise.
you could swap the sensor leads just to see if the other light flashes
you could swap the sensors

but if the fault is on both CH and HW then look for something common to both,
like the pump going slow,
or sludge in the heat exchanger(s)
or the auto air vent shut
or yet another baxi pcb faulty, flashing away like they do like it's still bleedin Christmas.
Chris said """You could measure the sensor(s), 11k ohms cold increasing on temp rise. """

I think he meant to say they are 11k cold DEcreasing to about 2k at 75*C.


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