Baxi Combi Instant 105e - no DHW problem:

[acument]

Hi,

can anyone assist with my problem ?

Combi Baxi Instant 105e - no DHW problem.

Slowly getting worse over the last month or so and now no DHW at all.

Good radiator heat all round.


When turning hot tap DHW pin clearly moves out.
no leds light on control panel (power led on) - no boiler activation, no DHW

Request hot water, manually switch microswitch (bic biro insert!) - same problem.

Turn on pre-heat, request hot water - slightly luke warm water flow to tap.

Have changed DHW diaphragm and both microswitches.

Any assistance / suggestions / troubleshooting diagram etc gratefully received.

Ta,

Keith.

 

[Rob]

If you've really proved the microswitch then surely it's a faulty PCB?

 

[corgiman]

If you've really proved the microswitch then surely it's a faulty PCB?

gotta be

being a Baxi Potterton its bound to be

 

[acument]

Damn that was quick !

I did think that this was probably the case - no way it could be the

247394 temp sensor ?

Ta,


Keith.

 

[corgiman]

Damn that was quick !

I did think that this was probably the case - no way it could be the

247394 temp sensor ?

Ta,


Keith.

well no as it doesnt tell the boiler to fire up but stops it on temperature rise

 

[acument]

Thank's again guys I'll replace the PCB and let u know how I get on.

Keith.

 

[namsag]

If the sensor is completely ******ed and saying temp already reached it will not let boiler come on.. There is 2 sensors heat and hot water switch them about to make sure before ordering pcb

 

[corgiman]

If the sensor is completely **** and saying temp already reached it will not let boiler come on.. There is 2 sensors heat and hot water switch them about to make sure before ordering pcb

surely even if the sensor was creamed the OP would still get the DHW demand light up on the front nam?

 

[namsag]

On a standard 105e yeah i agree the tap led would come on , but on the pre heat instant if sensor already thought hot enough would it not stop it coming on

 

[corgiman]

On a standard 105e yeah i agree the tap led would come on , but on the pre heat instant if sensor already thought hot enough would it not stop it coming on

but if the punter ia running the tap whilst the boiler is in pre heat mode the most he is likely to get is luke warm water as it dont comeon full bore for pre heat, what do you reckon?

I still go with knackered PCB

 

[namsag]

Yeah i reckon that as well but for sake of 5 mins and swapping sensors it may save 90 quid

 

[acument]

Will swap the sensors tonight and let u know how I get on

Thank's for your advice everybody - very appreciated.


Keith.

 

[namsag]

Reading over it again is the divertor valve motor working

 

[Agile]

Its so easy to simply check the sensors with a resistance check. That should be the first thing to do as its so easy.

As suggested you can easily take the motor head off the preheat diverter and see if the motor is moving the pin. However, I would not have thought thats the primary fault as I would have expected the DHW demand light to come on immediately there is a demand for DHW but you say thats not happening.

Tony

 

[acument]

Hi all,

swapped the sensors and also checked for open circuit - both ok, and same problem with no DHW.


Whipped the motor head off the preheat diverter and see if the motor is moving the pin - nope nothing happening there when DHW requested. The brass pin is finger moveable downward with some effort, I'm assuming here that the motor head pushes the pin down,there is absoutely no movement or vibration of any kind from the motor head.

Does that suggest it's the motor head, or a PCB failure which is causing the motor head to fail ?

Thank's for the effort guys.

Keith.