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Question - mend, repair, fix

Viessmann Vitodens 100 30kw combi?

Any help appreciated. boiler comes up with F5 fault .In book states burner blocked, check air pressure switch. ? Changed air pressure switch and now just doesn't show anything ? Common fault ?

November 2009

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Answers - mend, repair, fix

Hair dryer on outside of burning chamber really works. I have been accessing flapper through kidney shaped cover for years. This time it didn't work. But hair dryer on hot did. Keep away from wires Spenser's etc.

October 2015

Thanks for the tip worked a treat

December 2014

Just back from a week's holiday and found f5 fault. Hair dryer trick worked within a couple of mins. Thank you, can get on with post holiday laundry now!

November 2014

Worked a treat for me. Can't wait to rip this boiler out when I can afford it!

Thanks for sharing the tip Lewis.

August 2014

Hi guys any idea how to fix fd code

July 2014

The hairdryer and banging it worked! Thanks

November 2013

I replaced a radiator upstairs and when I tried to get the boiler fired up again it showed the F2 fault.. what do I do.. it's a Vitodens 100=w

steve rady
November 2013

red hot water at 1 tap (closest to the boiler ) no hot water down stairs

September 2013

Hair dryer worked a treat. great tip Lewis. many thanks. Just back from 2 week holiday to find F5 flashing at us.

August 2013

Just tried the hairdryer trick. Initially the boiler would not fire. So, as Lewis said, tapped the unit with the insulated end of a screwdriver and the boiler fired straight away. Thank you very much Lewis!

April 2013

OMG, thank you to the OP of the hairdryer tip! It worked a treat! I have been warned about THE FLAP before, the engineer said to put talc on it.

Thank you thank you thank you, now I don't have to wait 3 days for a bath and won't have to clean the kitchen ;-p

Sad Old Boiler
April 2013

I regularly had the same problem.
I fitted a 22mm Brass pipe fitting under the flap and the base to prevent it closing fully.
I unscrewed the union nut till it was exactly the right height.
The nut is secured with PTFE tape on the threads to stop it vibrating loose.
That way the flap does not stick ever.
The flap is to stop the passage of cooling air through the boiler when it is stopped.
A tiny gap by this method makes no difference.
The hair dryer works but the fault comes back to bite you at a later date.

February 2013

nice one, used the hairdryer and up it fired, the code has gone for now.. hope it never returns!

glen price
February 2013

You are the best,I spent hole day trying to fix the boiler, I took it apart, flooded my garage, lost couple of screws, broken couple of plastics and finally I found this post. Brilliant!!!!!!!!!! the hair dryer method works perfect. Thank you so much.

January 2013

My Boiler is flagging up fault FD any ideas how to help?

January 2013

Thanks to Lewis, a hairdryer and a few knocks we are up and running great. Thankyou

December 2012

My combi boiler will not switch on to the radiator mode what is the fault can you help

November 2012

hi, yes have the same problem with mine, i replaced the air pressure valve (ebay 14.99 brand new ) as it said was faulty - f5 code but still did not work, so i went on to google and found this site read all about it , tried what is said with air dryer and bingo it works -- so just a big thank you to all who has said try this ,

October 2012

How do I solve Code Fd on Viessmann Vitodens 100 30kw combi

August 2012

Excelent - another use for a hair dryer - took less than 2 mins of warming the drum

June 2012

The hairdryer trick does indeed work fantastically, but it's a temporary fix. The problem tends to recur, usually after a cold night, so find yourself standing there first thing in the morning shivering and late for work while you hairdryer your boiler! I guess a permanent fix would require taking the thing apart to clean or replace the sticky flap thing - presumably requiring a professional.

May 2012


Hair dryer worked a treat.

Your a star. Thankyou so much.

April 2012

Absolute hero, been stuck without heating and water all weekend and the engineer not coming out til tomorrow. Thanks!

January 2012

The power of the internet! Hairdryer worked a treat, coldest day of the year and now the boiler works. Excellent

January 2012

Hairdryer trick does work just done it I had the F5 fault code on my boiler, put the hairdryer on full heat for 2 mins being carefull not to melt any wires, waited until it was hot to touch then turned the boiler on and it fired up straight away...thanks guys!

January 2012

Hair dryer worked what a geezer you are Lewis.. Middle of winter storms and boiler packed in.. Lewis really you are THE man.. Many thanks

Singh A
January 2012

Can't believe it ..... This actually works !!!
Top Job :-)

October 2011

yup - solved the problem and money for me as well - many thanks

October 2011

Lewis - you deserve a medal! Hairdryer worked in a couple of minutes! Thanks - saved me a fortune in call out fees etc.

P from Kenilworth
August 2011

Thank you very much for the hairdryer idea! It worked!!! Just came back from a 2 weeks holiday and the boiler showed f5 error. Thanks again!

July 2011

Same problem and fault code here too. As we have boiler cover I called out the engineer, he arrived and stated that he would need to order a gasket before even removing the cover on the main heating assembly (to access the fan unit apparently). This would mean no hot water or heating until the part arrived, which was in three days!! So much for 24/7 cover.
I followed your hairdryer advice after he left and had the boiler running within seconds. Cheers guys, great help.

June 2011

hairdryer sorted it out for me too . great tip saved me a few pennies thanks a lot

ste darlo
April 2011

Hairdryer worked for me too, thanks a lot , great help

Ian B
April 2011

Lewis - thanks hairdryer treatment sorted it out (just as the British Gas homeserve guy appeared as well!)

December 2010

dont know whether this helps anyone but i had this problem friday just gone 10-12-2010 f5 flashing red light i took the front off the boiler and to the right in the top half of the unit is the fan it sits right at the edge and works its way back to the middle of the unit this is where the flap is sticking, i got the misses hairdryer put it on the hottest setting and ran it over the fan area and all the metal bits that are attached to the fan this allows the sticky substance that keeps the flap stuck open to release itself i left the hairdryer on for about 5 mins and turned the water on halfway through to help it to start up if it doesnt start up use the rubber end of a screwdriver and gently tap the fan and one of the other units this should sort it hope this helps msg me if your sucsessful (dont touch any wires as they will shock you ;-)

December 2010

If you still have the problem it is probably down to a flap that gets stuck. It's situated between the outlet of the fan and the inlet to the burner. I had the same problem everytime I left the house on holiday. When I came back, due to under use, the flap would be stuck. It has to be removed, washed & dried before replacing. A Gas Safe engineer will be able to do this quite easily as everything is accessible. Don't know about you but I've had my Vitodens for almost 4 years now and if I could afford to replace it I would! Viessmann made this boiler for the UK market without knowing what the UK market is like. Service wise, Veissmann are bad. They just didn't want to know. The independant engineer that came to my house knew what to do as he had one too. It's one of those faults that they are actually aware of but don't tell you. I ranted on at them for over an hour on the phone and in the end they sent me the replacment part. It was either that or pay £270 to call out an engineer to come and do it!

August 2010

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