Vaillant Thermocompact 637E Won't fire up

[Anthony Duffey]

Hi Guys

My boiler was displaying an error code F.33. I looked it up in the manual and it said:

"Main heat exchanger anti freeze protection mode due to no switching signal from the air pressure switch"

"Check air pressure switch, fan, fan supply or flue"

I called out a gas safe engineer out that was recommended by a neighbour. He said that there was an issue with the fan. As the fan was only replaced 4 years earlier and as I was considering replacing the boiler next year I decided to purchased a reconditioned fan.

The gas safe engineer came out and installed the fan. Everything was working great for about 5 days. One morning the boiler was not working and displaying F.37. I restarted the boiler and everything worked ok for another day until the F.37 code kept coming up on the screen every few hours until the boiler no longer worked.

Again I check the manual and it said:

"The rotary speed of the fan is too high or too low"

"Air pressure switch defect; fan defect; electronics"

I called the engineer back and advised him of the error code. I also bought a replacement air pressure switch ready for when he arrived.

He fitted the air pressure switch and called Vaillant and ran though their diagnostic over the phone. He advised that the fan was not working correctly so I sent it back to the place that provided the reconditioned part. They had a look at it and advised that it was working but they had replaced the PCB board on the fan with a different one.

The engineer came back again and reinstalled the fan. The boiler wont fire up and there isn't an error code appearing.

The engineer seems to think that the PCB board on the fan is the problem but can't guarantee it. The place I purchased the reconditioned fan from said that it must be the main PCB board as everything was working when it left them.

The diagnostic mode is showing that the pump is running and the air pressure switch is on. The fan is showing as being on but the actual rotary speed of the fan is displaying as 0.

I would like to find out what everyone thinks. Is it the fan at fault or the main PCB at fault? To replace both parts is going to be expensive. I think they are going to be about £250 a piece for a new one. This repair is becoming quite expensive when you consider the parts I have already purchased and the engineers time so far.

I would have hoped that the engineer would have been able to test the parts with a multi meter but this is not the case.

Thanks in advance

 

[denso13]

Don't know the answer but don't buy parts for other people to fit. If it goes wrong you'll do all the running around - as you have found.

 

[Anthony Duffey]

Hi Denso

Thanks for the feedback

 

[ianmcd]

Call valliant and get a fixed price repair think its about £270 and includes all parts

 

[AGAS]

haven't worked on one for ages but you could try diagnostic D33 which should give what the fan speed should be then D34 to see what speed your actually giving , has fan resistance been checked plus other checks need doing .
As said before ( denso13 ) getting parts second hand ( unknown resources ) your running the risk and not sending the fan with right PCB in the first place should of made you think . In your case it would be beneficial for vaillant fixed price as Ian has said above , by the time you paid for part ( original price ) and engineers time and hassle that £270 as stated becomes easier to swallow .

 

[hertsboilers]

haven't worked on one for ages but you could try diagnostic D33 which should give what the fan speed should be then D34 to see what speed your actually giving , has fan resistance been checked plus other checks need doing .
As said before ( denso13 ) getting parts second hand ( unknown resources ) your running the risk and not sending the fan with right PCB in the first place should of made you think . In your case it would be beneficial for vaillant fixed price as Ian has said above , by the time you paid for part ( original price ) and engineers time and hassle that £270 as stated becomes easier to swallow .

Also check D24 to see if the air pressure switch is made.

 

[Hason]

Fan and aps! Check flue is sound, fairly straight forward job good luck

 

[AGAS]

Also check D24 to see if the air pressure switch is made.

+1 thought the engineer would of checked that by terminals ,( you hope )

 

[Anthony Duffey]

Thanks for the advice guys.

I have to agree a fixed price repair of £270 is not bad at all. I was prepared to pay around the £200 to £250 mark for a fan so it seem reasonable to me. I will give them a call first thing and I will let you know what they say.

Cheers.

 

[Agile]

I can never understand why people are so keen to buy repaired ( not reconditioned parts! ).

If they don't work properly and that seems very common then there is a lot more work involved in multiple changing of parts.