baxi combi instant 105e no ch

[ZAD]

HI
can anyone help me pls.
i have a baxi combi instant 105e (no flashing warning lights on)the ch does not work unless i take out the dhw green wires too the heat sensor .Then the ch will come on any help will be appreseated

 

[Agile]

Have you measured the resistance of the sensor with the boiler cold?

The sensor may have failed low resistance although this is rather unusual.

On your model the MO is a little different and there are more possibilities for faults.

Tony

 

[ZAD]

no but i have just changed both temp sensors for new ones still the same problem pull out wire too dwh temp sensor then ch comes on

 

[baxpoti]

Has anything else happened/been done to the boiler prior to this problem?

 

[ZAD]

no nothing has been done

 

[diverdee]

strange one look forward to the answer to this one .when u changed the thermistors you have put them in place i hope not just left them hanging as this makes a difference

 

[diverdee]

its not a 105 instant is it ?

 

[ZAD]

no lol thats like asking have i put the plug in the bath .I have installed them properly and yes it is a baxi combi instant 105e

 

[diverdee]

lol ok sorry just checking just some people dont realise they flow switch as well.not too sure on the instant but sounds like maybe the pcb thinks it needs to preheat the water all the time.even when its up to temp

 

[ZAD]

iam a pipe fitter by the way lol

 

[diverdee]

have u turned the hot water control to off or low this disables the preheat!! then try your heating

 

[ZAD]

no temp control half on

 

[baxpoti]

some people dont realise they flow switch as well.

Twice you have mentioned this, what do you mean?

 

[diverdee]

try turing hw control to a minmuim then try heating.

 

[ZAD]

tried that and tested micro swiches and thinking may be pcb and as i have put in orignal post its strange if i unplug dhw temp sensor i get ch and flashing neon to tell me that dhw temp sensor fault