My Ferroli Modena 80E combi boiler keeps switching on & off?

had same prop. british gas eng says common prob he adjusted the ignition pressure on pcb

john
February 2014

Hi John,
Well my earlier reply was more of a question so after a bit of work (and now the heating is running like a dream) here is more of an answer:
1) I changed both the venturi and the test point in the fan; whether this was absolutely necessary I don't know (the test point is the small piece of plastic tube at the bottom of the fan I spoke about in the previous post). I reckoned this might be important to ensure correct air flow through the air pressure switch.
2) As many people say, changing the thermistors; it's a pretty simple job draining the boiler to do this, you can simply turn the mains water off and empty the hot water taps for the DHW.
If your'e a bit unsure (like me) about draining the CH the manual will say 'The C.H. is drained via the pressure relief valve (twist about 1/2 of a turn)', you can simply locate the drain point on the lowest radiator, empty what you think may be a boiler full of water out, then open up the bleed valve on the radiator nearest to the boiler. That should do it.
Thermistors are cheap, need a 15mm spanner and/or a pair of long nose pliers, change them over and Bob's your uncle.
Turn the water back on, refill the system from the filling loop to about 1 bar and bleed radiators where necessary.
For roughly £30.00 or so, this simple operation has made my house cosy, snug, warm and (most importantly) kept the wife happy.
Good luck.

Stuart
January 2011

hi john! had the same problem, it was thaugh to be the venturi or the air pressure switch, it turned out to be pcb. (the ignition board) hope this help's.

C
January 2011

Well, I've had the same problem getting progressively worse, so I thought for a tenner I would change the venturi, which I did, but the problem persists.
I did notice, when replacing the fan, that the lower red air pressure hose nozzle was loose in the fan housing. Again, like the venturi, this has hardened though, thankfully, not crumbled.
I have managed to turn it round a bit in the housing to help hold it, but it's probably come loose again as soon as the boiler has been on for a bit (which sometimes it does). This lower hose is, I would imagine, the inlet for the air pressure switch as I assume the venturi creates a vacuum that draws the air through (correct me if I'm wrong) if so it would be drawing air from outside the fan as well which may create uneven air flow?????
Does anybody know if I can change this part as I don't want to buy a whole fan just for one bit of plastic?
Even if this isn't the underlying fault it still needs to be rectified.
Cheers
Stu

Stuart
January 2011

just finished repairing my bioler just as its says above it kept going off and on hot water never hot enough and also the C/H with the same ,so bouhgt a Venturi Kit on Ebay for £10.99 plus P+P took 10 mins to do now the wife is happy again .this is a great site thanks to all that use it :-))
if your not sure where parts go just tipe in the make and model of bolier and search for diagrams all for free on the net

Tony Npt WALES
November 2010

remove one of the discs from the top of the combustion chamber then try the hot water. if it runs withiut cutting out, then replace the venturi in the fan. repalce it with a 'brown' venturi, not a red one.

ciaran
October 2010

This might help others in the same position. My boiler was doing exactly as the OP - switching on for a few seconds and then cutting out. But it was also very cold and the CH wouldn't heat up properly. Sometimes it ran OK-ish but was still chilly.

I took out the PCB and found deep pitting around the connectors where there was clearly an annular crack all round some of the pins. I took off the old solder with a solder sucker and re-soldered them. Better? Maybe, maybe not. Still cold, still cutting out.

Next, I checked the voltages across the CH thermistor and found that it seemed to suddenly jump just as the boiler cut off (when it wasn't on-and-offing) and this seemed to suggest the thermistor was faulty. I guessed that if the thermistor is disconneced, the voltage jumps and the boiler detects this as unnaturally cold and cuts out. So if the thermistor is intermittently open-circuit, this would occur. So I replaced both thermistors (might as well) and now I was warm again.

But it still would go into the start-stop-start business again both for CH and DHW which is a pain if you're in the shower as it goes from steaming hot to freezing cold.

A friend helped and we came to the conclusion that it had to be something to do with the fan. We checked this by artificially shorting the pressure switch contacts immediately the boiler lights. When we un-shorted them, the boiler immediately cut out. This meant that it was DEFINITELY the fan/switch.

We took the fan out and checked it out. It seemed OK. So we put it back and it was really bad. So I tried to pull off the hoses and the venturi just crumbled.

This is a plastic tube with a constriction that generates a small vacuum when the air is flowing. This is offset by the other pipe which picks off the fan housing pressure: one slight pressure and one slight vacuum. These feed the pressure switch to positively check that the fan really is working.

I couldn't get the spare venturi, so I just replaced the entire fan. I got it from sales(at)allsparesdirect.co.uk through eBay. It arrived next day. I installed it and now the boiler works a treat.

I've also ordered the venturi kit. That way, I can get the old fan working if it ever needs to go back in!

Richard Aston
January 2010

Chris Finch is right. Dry solder joints, particularly on the relay and the connectors are a regular feature of my Modena 80E control PCB.

They look fine to the naked eye but try using a magnifying glass or jeweller's eyeglass.

The symptoms I got were the same as the OP's.

Clean to old solder off with a sucker and then re-solder with the old-fashioned tin-lead stuff.

Richard Aston
January 2010

boiler tries to start up fan goes sparking up ok then goes make a
ocoilating noise and goes into red fault lock out this only happens when it cold ok during the summer.
I have changed the thirmisters
please some one help me i,m a sparks out of work at the moment no money coming in .
Fitz

fitz
November 2009

where can you get the fan kit from ???? Finding it hard to locate one

dean
November 2009

change thirmisters on water and heatingmick

mick
September 2009

had this loads of times renew the ventura in the fan and it will run perfectly. It is a type of hardened plastic and becomes distorted which then creates uneven pressure at the pressure switch which then causes it to bounce.
You need to remove the fan to renew the ventura and the kit costs approx ten pounds, change the inlet and the outlet while its out. The existing one will crumble as soon as you touch it.
You will also find the boiler will run without cutting out if you remove the inner silver casing but it should not be run for long as it is unsafe to do so.
Hope this Helps
Gary

Gary Hunt
July 2008

I found a solution eventually. It was to call Ferroli and get them to service it. They found several problems, then came back and changed several parts. Their fee was reasonable, and now it works fine.

John Widdop
April 2008

Does anybody have a circuit diagram for a 24i ?

kbkearney@hotmail.com

kk

kevin
February 2008

did you have any luck with possible solutions as mine is doing the same

fisher2312@hotmail.com
February 2008

SOUNDS LIKE A TEMP SENSOR FAULT. THERE ARE TWO ON THE MODENA. EASY ENOUGH TO CHANGE AND CHEAP TO BUY. PULL THE LEAD OF THEM ONE AT A TIME TO SEE IF THE FAULT STOPS. HOT WATER HAS TWO GREEN WIRES CH HAS TWO RED WIRES. GOOD LUCK

BREEZY
January 2008

Hi
I had one of these in my last property. Had loads of plumbers sucking air in through their teeth!
Asked a sparky who said have a look at the PCB (circuit board) and hey presto dry solders all over the place and especially on one of the relay switches (which controls the burner!!) It was fine after getting them all soldered up. I did it myself but I know what i'm doing with a soldering iron and know my way around a circuit diagram. Best of look

Chris Finch
December 2007