Boiler experts please

 

I've got a baxi 105e boiler with a fan/flue fault

 

Pretty sure it's not the fan, almost certain it's the board that was replace around 2 yrs ago. From reading on the net it looks like that it the life span of the baord. I'm an electronics engineer by trader and certain its a fooked relay, but wich one ?

Does anyone have a main board for the above bouiler I could borrow to test it before forking out for a board ? Long shot I know but I suppose it's worth a try.

 

CheerZ in advance

Paul

why do you think its not the fan

why do you think its not the fan

 

 

Put meter on fan, voltage goes up for a split seconf then dies

Sometimes the fan will start for around 10 seconds, gas fires up and everything but then fan stops and fan/flue fault neon comes on again

i found this on the baxi site, i dont know if this is what you have tried

http://www.baxi.co.uk/products/literature/Baxi-Combi-105HE.pdf

Just had a similar fault with an ideal boiler - was the bearings on the fan motor being seized so the fan wasn't firing up properly...

Just had a similar fault with an ideal boiler - was the bearings on the fan motor being seized so the fan wasn't firing up properly...

 

 

The bearings 'seem' fine Andy, you can spin the fan by hand and it rotates very freely and does several revolutions.

i found this on the baxi site, i dont know if this is what you have tried

http://www.baxi.co.uk/products/literature/Baxi-Combi-105HE.pdf

 

 

 

Yeah I've got that, Im getting fan/flue fault as described on page40, Goto section E but it all seems to check out ok. The pressure switch and flue is out of the equasion as the fan isn't starting.

does the fan always start but the boiler fails to light or lights then it shuts down

Go back to the fan pressure switch and check the terminals with the cables disconnected ( power off ), it could be the switch is getting stuck in the fan proved position ie. fan running even after the fan has stopped, if this is the case the the fan will be prevented from running again as part of the lockout proccedure.

 

If the fan occasionally runs and the gas valve fires up then dies the air switch again could be the culprit.

As far as the control board is concerned I have had a BAXI 105e for over 7 years in my previous house with no real problems and now have a fully condensing version of it in the new house, I would always check other areas

 

 

 

There is a set proceedure for testing this all out but be careful your not infringing safety gas regulations, I know it is a ball ache but they are there to protect you.

 

 

 

Daveman

Sorry missed a bit :

 

As I was saying

I would always check other areas BEFORE blaming the pcb, electronics are so much better now and board faults are rare, unless your a plumber of course ( note I did not say engineer)and the boiler is a customers!!!

 

 

Daveman

I Have not got a pcb but if you need one let me no and will get it trade from parts centre poss one near you ;)

 

Dave

Oh part number 248731 baxi no or parts center no 424068 ;)

 

 

There is a set proceedure for testing this all out but be careful your not infringing safety gas regulations, I know it is a ball ache but they are there to protect you.

 

 

 

Daveman

this is the problem mate, i would do a certain procedure to determine if its the fan or pressure switch but its infomation that cant be given out to people who shouldn't be messing with gas boilers

does the fan always start but the boiler fails to light or lights then it shuts down

 

 

Lets start from here.

 

No the fan only starts say 1 out of 30 times, spins for around 3 second, gas fires up then off. All other times the fan spins around 1/4 revolution then stops.

 

DaveMan, I have tested the switch (blowing down the pressure pipe and sucking (leave it :slap: ) the vaccum pipe and the switch appears to work ok and have metered when the switch switches and that seems fine also.

 

DaveMan, Yeah I was hoping it was something other than the PCB but having read on the net the relays fail after around 2 - 4 yrs (board was replaced 2yrs ago) if I can find out what relay, no problem.

 

yewcheck, you got a board I can borrrow for further testing ? although I think the part number for my board is AFAIK

 

 

CheerZ all

check for play in the fan i had this on a worcester boiler the fan would spin some times and other times it wouldnt. the boiler would light as yours does then the fan would jam up and stop, in the end it was the bearing in the fan. i could spin it but when it powered up the fan this pulled the bearing off line stopping the fan

check for play in the fan i had this on a worcester boiler the fan would spin some times and other times it wouldnt. the boiler would light as yours does then the fan would jam up and stop, in the end it was the bearing in the fan. i could spin it but when it powered up the fan this pulled the bearing off line stopping the fan

 

 

Bearing seems fine, what will happen is power will be applied to the fan for a split second, hardly registering on my meter, then no power at all and fan continues to spin freely for around 1/4 - 1/2 a turn

then i would refer to section D do them tests and that will tell you your problem

then i would refer to section D do them tests and that will tell you your problem

 

 

Interesting, section D, and looking at the PCB it's looking like either 1 of 2 or both relay RL5 and/or RL6

from my supplier your looking at £74 plus P&P if yours is the 105e combi instant or if its the 80/105e combi both the same price for PCB

Check the live and neutral have not been connected wrong way round, had this on a boiler that would run for a few secs then cut out, connected them as should be and boiler ran O.K.

CheerZ dipone, 105e, not instant.

 

Anyone know where I can get the schematic for the PCB from ?

Well I found the duff relay, RL1, took the cover off, it has burnt out contacts. But I also burnt out a transistor on the board testing the other relays :rant: :headvswal So, does anyone have a duff, knackered board for a Baxi boiler they don't want I can use to replace the fooked components ?

 

CheerZ

Paul