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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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I have a problem with a baxi 105e combi. When hot water tap

Resolved Question:

I have a problem with a baxi 105e combi. When hot water tap is turned on the extract fan starts, the air pressure switch operates then the fan slows down and then a second later the cycle repeats. After about 12 seconds the indicator above the fan symbol starts to flash. This continues from anywhere between 20 second and 5 minutes before the burner fires up and the light stops flashing. Any suggestions?
Submitted: 2 years ago.
Category: Appliance
Expert:  Plumberpro replied 2 years ago.
Plumberpro :

, does it do this on heating as well ?

Customer:

Yes

Plumberpro :

, can youbhearcthe boiler attempt to light by sparking?

Customer:

No

Plumberpro :

Ok , your boiler has a viewing window.but you have to take the front cover off first . would you be able to take this off?please

Customer:

ok done this

Plumberpro :

Ok . if you turn the boiler off and back on. Open a hot tap and look through the window. Listen fan running and any sparking , attempted lighting. Thanks

Customer:

Fan starts o run at full speed, click heard from air pressure swich, then fan slows down No sparking. Then fan starts up again d same click isheard from air pressure switch and still no spark. This sequence keeps repeating. Fan sounds like an engine reving up. This cycle goes on while and then sometimes the boiler fires up after 10 sec to 5 minutes.

Plumberpro :

, it sounds like your air pressure switch is making but if it fails to make contact then the sequence will start again and again. This will be either a weak fan or faulty air pressure switch. The fan is quite expensive compared to the APS

Customer:

I have fitted a new air pressure switch and this made no difference. Could it be a problem with the pcb?

Plumberpro :

Its possible. What you could try first . is gently blow down the fan to APS tube operating the APS and see if the boiler works correctly. This will prove its acfaulty fan or not. Let boiler start the fan then blow to operate aps

Customer:

Tried this and sttill the same responses

Plumberpro :

Its the fact your getting the fan fault symbol that is pointing to the fan area. On the functional flow diagram in the manual it shows the temp sensors next in line . before replacing the board I would check these first . do you have a multimeter?

Customer:

I can get one. But won't be able to do any checks tll after 3pm today. What should I read from theses sensors?

Plumberpro :

Ok range of most are between 2000-40,000. At room temp look forv9 to 11 kohms as temp rises will go down to about 2k as temp goes up may go up to 25k . really looking value.

Customer:

Problem turned out to be pcb. Changed this and all is well. Thanks help any way

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