Ariston Microcombi 23 MFFI (or 1)

[tonybhoy]

Hi guys.

Called out to one of these today and just looking for some advice.

Boiler's two green lights are both on, the reset (red) light is not.

Pressure is fine.

Graslin mech timeclock on boiler which is on (24hrs).

No heating or hot water on demand.

Power going to the board and the PCB fuses(2 of) look to be ok .

Nothing else works when you run a tap or switch on the clock.

My thoughts are that the is PCB faulty.

Thanks in anticipation for any replies.

Tony.

PS,anyone any idea how old these boilers are?

Serial number is 1005352362320435500329.

I'm guessing the year 2000 from the above number.

Tony.

 

[Gasguru]

The water pressure switch needs at least 0.7 Bar but they can drift requiring higher pressure, or perhaps it's faulty. I think they have a 3 contact APS, perhaps the NC contacts are high resistance.

 

[Whiter]

Is there 240V to pump? I think these have a differential pressure switch that makes when pump runs, so if pump not operating then nothing happens.

 

[Gasguru]

No, these are basic bi-thermal heat exchanger boilers...no diff pressure sensor, just a static pressure switch.

 

[tonybhoy]

Is there 240V to pump? I think these have a differential pressure switch that makes when pump runs, so if pump not operating then nothing happens.

Don't know to be honest-never checked-but the pump isn't working nothing is.

Just presumed that with nothing working-pump/fan-for both heating and hot water that the PCB was goosed?

Thanks for the reply.

Tony.

 

[tonybhoy]

The water pressure switch needs at least 0.7 Bar but they can drift requiring higher pressure, or perhaps it's faulty. I think they have a 3 contact APS, perhaps the NC contacts are high resistance.

Plenty of water pressure on the mains at the cold tap and on the hot.

Fan has to be running before the APS will make though doesn't it but it's not.

It's a fairly simply boiler in my opinion.

Sequence being,I think-demand for heating/hot water power to pump-power to fan-APS makes-power to gas valve then boiler ignites,correct?

Thanks for the replies.

Tony.

 

[Kristoflampie]

Thermistor problem...... cuts them out and makes them stand still, check with meter on 20k scale resistance, if its open circuit on either heating or hot water thermistor nothing happens .... it just sits waiting.

 

[tonybhoy]

Thermistor problem...... cuts them out and makes them stand still, check with meter on 20k scale resistance, if its open circuit on either heating or hot water thermistor nothing happens .... it just sits waiting.

Cheers.

Had a bloody thermistor with me too (Vokera one) but it was down in the van and I was on the top flat of a tenement

Thanks for the reply.

 

[Gasguru]

Tony, from you Olympic postings I assumed you were an old hand at boiler repairs. What has the pressure at the hot and cold taps got to do with the primary side water pressure switch.

On a 3 contact APS the normally closed set have to be prooved before the fan starts ie check resistance. The board won't run the fan if it thinks the APS is "activated".

 

[tonybhoy]

Tony, from you Olympic postings I assumed you were an old hand at boiler repairs. What has the pressure at the hot and cold taps got to do with the primary side water pressure switch.

On a 3 contact APS the normally closed set have to be prooved before the fan starts ie check resistance. The board won't run the fan if it thinks the APS is "activated".

Sorry mate read your post wrong.

I am an old hand but normally only do boilers installations with the occasional repair of some of the older boilers ,Mexicos ,thorn apollos,kingfishers and the odd Vokera combi.

However the young girl who called me today seemed ok and it did appear that it was simply a system pressure problem as in she didn't know how to re-pressure so I kindly offered to help her out but as usual you get in a wee bit deeper than you had anticipated so I'm trying to fix the bleeding thing now without resorting to calling Ariston tech in the morning.

I've a load of rads to fit tomorrow and for the next three days,last thing I need is to be tied up with throwing parts at a boiler.

I am about ready to tell her she needs a new boiler

 

[bengasman]

Another model favoured by adventurous diy and cowboys.
Rarely flushed with expected results.
Gauge pipe very thin and prone to blocking, top up the pressure and see if it moves at all.
If the fan does not come on, this is probably your answer, or check the pump speed and torque.
If fan does come on, check if aps switches, if it doesn’t, force it. only for test of course.
If you don’t know the trick, ask in the CORGI only section of the forum.

BE CAREFUL WITH TOPPING UP! it would not be the first one where the knob falls out when you turn it open too far.
Easy boiler to work on, but it is a piece of junk.
And be careful not to cut yourself, sharp burrs everywhere.

 

[tonybhoy]

"

Another model favoured by adventurous diy and cowboys.
Rarely flushed with expected results.
Gauge pipe very thin and prone to blocking, top up the pressure and see if it moves at all"

That is another problem.The pressure has been sitting at 3 Bar since November,according to the girl who called me out,but lately it has been dropping down to below a bar then going up to 3Bar again.

Turns out the filling loop valve is passing-hose connected-and is continually filling the system but the PRV is phucked which is continually dropping the system pressure

No wonder I don't get involved with these things.


"If the fan does not come on, this is probably your answer, or check the pump speed and torque.
If fan does come on, check if aps switches, if it doesn’t, force it. only for test of course.
If you don’t know the trick, ask in the CORGI only section of the forum."

Yeah I know the trick,I think.

Are we talking kissing here?LoL.

"BE CAREFUL WITH TOPPING UP! it would not be the first one where the knob falls out when you turn it open too far.
Easy boiler to work on, but it is a piece of junk.
And be careful not to cut yourself, sharp burrs everywhere.

"

Your not wrong there mate.Just getting at the electrics was 'challenging'.

Just going to go to my supplier in the morning with whom I have a very good relationship and get a board,APS and the thermistors on appro.

I'll start with the thermistors and take it from there.

Suppose I should get a pump too but I'll just change the head.

Thanks everyone for your replies.

Really is a great board this I have to say.

I'll up-date tomorrow.

Cheers,

Tony.

PS sorry if this post is a tad jumbled,don't really know how to work the editing stuff properly yet.

Must get myself onto the Corgi section sometime this week too.

 

[tonybhoy]

Hi guys here is an up-date for anyone interested

Contacted Ariston tech this AM who told me that heating demand starts the pump and hot water demand starts the fan therefore the PCB is gubbed,hey say,cause there ain't nothing happening with either demand.

Spent about an hour and half sourcing parts phoned the girl with a price and basically she blanked me.Think she thought I was at it,her loss.

Not best pleased but that's life,up wards and onwards as they say.

I have a serial number for the boiler and after speaking with Ariston who told me how they work the serials I can post this info if anyone wants it.

Basically the number tells you when, where and on what date the boiler was made.

Thanks to everyone who replied.

Much appreciated.

Regards,

Tony.

 

[Rob]

Did they get you to test the low water pressure switch?

 

[tonybhoy]

Did they get you to test the low water pressure switch?

The guy mentioned that but when I told him nothing was happening at all full stop as in nothing coming out of the board, then he said it was defo the PCB for the reasons above.

I.E. hot water demand no fan on and heating demand no pump on.

He said it was nothing to do with the thermistors or the APS.

Presumably he discounted the pump and the fan being faulty separately cause basically they weren't doing anything when there was demand, for example pump would bring on the fan and fan would bring on the pump.

Obviously I've been unable to test his advice seeing that I was slung,LOL.