Prima F50 Problem, Lack of sparks?

[JLneonhug]

Hi everyone, I've been skimming though the forums to find a solution to my particular problem, however i've tried all the quick solutions and no luck

The Problem:
~ Previously timed started not to work on a warmish day (few days ago)
~Quick fix solution was:
a) push the timer heater ourselves and that seemed to work
b) take out and put in the tray of the boiler and it restarts with the buzzing noise and sparks up
~ a week on I found it wasnt working so i decided to take the tray out and inspect. It seemed like tapping the thrmostat part of the boiler helped spark it up (where the air pressure and the thrmo is)
~ Now with the tapping (actually hitting it with my finger) of the thrmostat/air pressure part it makes the buzz noise, running water works (presuming pump works) but it doesnt have a sparks to light the gas.

Notes:
~ No loose connections on the boards, no burning smells or anything
~ Once the boiler was on you could switch it off and on again manualy without any problems
~ Fan should be working (didnt know there was one but i hear the usual noises except the roaring of the flames)
~ No visible flames are there
~ Its very cold in the mornings!!

If you have any suggestions or help that would be great! thanks for your time.


-John

 

[Timmyturtle]

You say no loose connections...you could try this 407677 pcb or similar
Where the main plug (7 pins with a blank one in the middle)connects to the Pcb ,front of the board..look underneath the board at the solder joints.
Look for any signs of cracks around the solder and resolder if needed.
You will have to remove the pcb to see this area properly ( with the power off)
You might be able to wiggle the connector and hold,to one side ,( front/back) and see if it works before you remove the board (this sometimes works but not allways)Remember there are live wires in there

 

[gas4you]

I would suspect the air pressure switch if you have to tap it, although the buzzing noise usually is a relay on the pcb which would also control the ignition. Have you tried tapping the relays on the pcb whilst it is buzzing?

 

[Timmyturtle]

The buzzing...could it be the noise of sparks trying to make a contact?
I did have one that was arcing and making a buzzing sound.just a thought.

 

[kevplumb]

tin of sparks

 

[Soggy_weetabix]

tin of sparks

Kev, I do laugh with your comments.

I would suspect pcb by the way.

Your analagy (sic) of combustion on netaheats should be put into any gas engineers 'bible'.

Today was my last day for 2 jobs I dont wish to undertake again so im feeling euphoric...

a Vulcan heat ex (came out of stock)
the good old 'sooty'

Just left the bathroom looking like 80 coal miners have had a conflab in there and the missus aint happy.

Can I have my head stroked...peerleease?

David

 

[kevplumb]

had a few of them dav

consider your head stroked by a hairy arsed geordie pipe fitter bonny lad

 

[Soggy_weetabix]

had a few of them dav

consider your head stroked by a hairy a***d geordie pipe fitter bonny lad

Cheers. Your one of them hairy bikers aint ya???

Consider my head massaged.

Good man!

Dave

 

[JLneonhug]

Hi, Thanks for the replies, I've checked the PCB, it looks very new without any loose solder joints or anything, the only thing is that the top part of the circuit (i.e. air pressure/thermostat etc etc..) that is making the buzzing noise, and that seems to "reset" itself everytime i gently hit it... I've tapped the pcb (only the box as its been glued down) and the square metal object next to it, it seems to not do anything. I tried playing with the air pressure switch aswell while switching it on and that also does nothing (blowing and pushing button).

Want to take the top part of the circuit off but it seems to be connected to another panel and a copper wire of some sort leading into the boiler.

Relay is arcing? i did suspect the buzzing noise was from a relay (and the tapping helped kick the switch over)

[Edit] ok i found the relay, it was buzzing alot then it stopped after about 20sec's.

 

[Timmyturtle]

You took the pcb out to look at the solder joins right?
I carry a couple of these boards ,that had this fault,that i have fixed so it must be a fairly common thing.
You have checked the fuse on the pcb ?
Could you post the pcb part number ? just to see which one it is,thanks

 

[JLneonhug]

Checked the fuse, seemed fine, part no. is 407677. How did you fix the board?

 

[Timmyturtle]

These were fixed by resoldering the 6 connections under the board...but you state these look ok
What i noticed on the ones i`ve done was a hairline crack around some of these solder "blobs" . they are not very obvious cracks,a magnafine glass would help.
I have also fixed a couple and put them back on the boilers and seem ok now
In fact the last one i did i used the customers soldering iron and solder, coz they just happened to be next to the boiler
Did wedge the connector over on one with a match and it was ok till new board fitted a week or so later (that was the first one i found and still have that board as a tester-after resoldering its connections)

 

[JLneonhug]

Ok after taking the whole thing apart i've found out what was making the buzzing noise, it was the thermostat thing (variable resistor with some copper wire presuming thats a thermistor of some sort?). I believe thats to be at fault as i cant read the resisance value on it when its actually on (i.e. everytime i tap it; it will jump to a value of 2M Ohms then jump to strange numbers then back to greater than 200M ohms). Could anyone clarify me that this isnt normal? Also, does anyone know how to remove that as the copper wire is connected on quite securly on the vari. res.

Thanks for helping! hope this is the problem so i can get warmth back into the house!