Help! Fridge problem

SeamusG97

My van is just recently out of storage and destined for the boat this Thursday.
Murphy's law has kicked in with the fridge as it has started to act up a the last minute. It is a Thetford N145 which has automatic changeover to gas and has automatic piezo ignition.
The problem is when it switches to gas, the flame ignites as it should but the piezo keeps on firing until it times out and shuts down again. I've taken out the fridge and dismantled and cleaned everything but no difference.
One thing that puzzles me is that I can't find the thermocouple - there isn't one listed on the thetford parts manual and there isn't anything in the burner area besides the ignitor. Instead there are two tubular components that run down the outside of the 'chimney' tube. One has a thick blue cable running to it an the other has two black wires - is one of these a thermistor? Here's a link to a picture of something similar.
http://www.ebay.co.uk/itm/THETFORD-FRIDGE-ELEMENT-CARAVAN-MOTORHOME/271922955666?_trksid=p2047675.c100011.m1850&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D32333%26meid%3Dbe5bf43718d64d9691bf6b3a653ba3ba%26pid%3D100011%26rk%3D1%26rkt%3D10%26sd%3D271916223477

Are they user replacable parts?
Any help appreciated.
Thanks
Seamus
Edit:
Ok - so I've been doing some reading in the meantime on how absorption fridges work and I think that these items are heater elements - one for 12v and one for mains? That makes me even more confused as I can't see any sign of a thermocouple - how does the unit sense if the flame is lit?

SeamusG97

After even more reading it appears that the spark electrode also acts as the thermocouple but I'm not clear on how. Therefore the problem may either be a faulty thermocouple/electrode ( or worse ) a faulty PCB. I guess the next step is to replace the electrode. Does it look like i'm on the right track?
I guess that it is a standard item so the next question is where can I find one tomorrow?

Aidan_M_M

yes , it does both jobs . The other devices you mention are the DC and AC heating elements. I;ve had to replace quite a few of the PCBs , there is a design flaw with the case , which lets water run into them . Thermocouples rarely give trouble tbh . Was anyone at it , that may have moved it?

SeamusG97

Aidan_M_M wrote: »

yes , it does both jobs . The other devices you mention are the DC and AC heating elements. I;ve had to replace quite a few of the PCBs , there is a design flaw with the case , which lets water run into them . Thermocouples rarely give trouble tbh . Was anyone at it , that may have moved it?

Thanks for the reply.

No - I've had the van from new and it hadn't been disturbed until now. I opened the PCB case and it doesn't look like any water has gotten into it. I also loosened the thermocouple and moved it around a bit to see if it made any difference - it is up to a dull red heat when the flame cuts out so it is getting plenty of exposure.

I need a fridge for five weeks away so maybe I should just replace both thermocouple and PCB as a belt and braces solution? If so would you have the bits I need?
Thanks
Seamus

Aidan_M_M

When was it last serviced , burner cleaned etc?
there are different boards and TCs , would need the data from the sticker inside tbh.

SeamusG97

Cheers.
Last done by me just now - dismantled and cleaned all the burner related bits including the flue. It was fairly dirty and had been well overdue a service. I'd be embarrassed to say how long it was before then......

I'll pull the unit out and get the information from the stickers in the morning.

Edit: here they are:

Model: Thetford N145-N51H06R6A
Power Board: PB0812000850631603

Thermocouple:
I've a picture but it won't attach - it's an L shaped one that looks like this:
http://www.thethetfordcentre.co.uk/sp-fridge-spark-electrode.html

SeamusG97

Aidan_M_M wrote: »

When was it last serviced , burner cleaned etc?
there are different boards and TCs , would need the data from the sticker inside tbh.

Thanks for the advice when I called out today for the spark electrode.
I cleaned up the burner a bit more with a wire brush and emery. Fitted the new electrode and away it went.
Now I just need to put back all the bits and pieces that came off to get at it in the first place.

I'll talk to you about getting a proper service and maybe a damp check sometime after the summer.
Thanks again for your help and keep up the good work!
Case Closed.

Seamus

SeamusG97

SeamusG97 wrote: »

Thanks for the advice when I called out today for the spark electrode.
I cleaned up the burner a bit more with a wire brush and emery. Fitted the new electrode and away it went.
Now I just need to put back all the bits and pieces that came off to get at it in the first place.

I'll talk to you about getting a proper service and maybe a damp check sometime after the summer.
Thanks again for your help and keep up the good work!
Case Closed.

Seamus

Maybe not quite as closed as I had thought. Gas works fine. But now the fridge won't switch over to 12v when the engine is running. It dithers between gas and 12v and settles on gas. If forced to 12v, error codes
Suggest that the engine running detect input isn't high or undercurrent on the 12v circuit. I had the entire unit out a few weeks ago so the starting point in my thinking is what I disturbed. I understand that the fridge needs a 12 v supply and an engine running signal. My multimeter died the week before I left so I haven't any
way of reading any of these apart from a circuit tester that seems to indicate that all inputs are high.
Maybe just buy an European gas bottle and new regulator when the beer goes warm?