Thetford Fridge 3-Way on Gas

[Webby]

The auto selector can cause problems. I think there is a delay so that if you are on battery and pull in for fuel the gas does not spark up as soon as you switch the engine off.
We always use manual selection......................even then when changing source to gas we have to leave it switched off for a while.I guess the delay function still kicks in.
As said keep the burner area clean, but also we find it sometimes needs a rap on gas regulator or solenoid which can stick and stop the gas coming through when required.......trace the gas pipe back from the burner

 

[Forresbroons]

Not sure if this is the problem but I remember reading somewhere about a time delay on some auto fridges when switching over to gas, to prevent the gas circuit from lighting when stopped for fuel top up and the likes.
Just thought it was worth a mention.

 

[wildebus]

Not sure if this is the problem but I remember reading somewhere about a time delay on some auto fridges when switching over to gas, to prevent the gas circuit from lighting when stopped for fuel top up and the likes.
Just thought it was worth a mention.

Hi. Thanks for the thought but no, it is not that.

I will add some info on this though as an FYI as the Thetford display is very confusing in that situation and the following might be of interest to other Thetford users ...
When the Fridge is in Auto and using 12V Battery, there is a 15 minute delay once 12V power has gone before the fridge tries to start up on Gas (for safety in petrol stations as mentioned). The Thetford fridge however does SWITCH to gas immediately 12V goes away as far as the display indicator is concerned and the lights would suggest the gas is running, but despite that, there IS a 15 minute delay before the fridge electronics opens the gas supply and the ignitor starts clicking away.

(A Dometic 3-Way Fridge with Auto Energy Switching is different in that it doesn't show the gas as operating until it actually is on the switch over)

 

[mr brown]

Fridge on AC all night and temp went down to a steady recorded -1C, so it is cooling (actual temp not sure. I had to extend the sensor cable and that might have affected the reading slightly as temp based on voltage drop on cable. Also sensor direcyly on cooling vanes, not ambient (did that as that is how the fridge's own sensor is attached so can compare temp to power use (on AC anyway))).


Turned off AC and fridge didn't start up as it switched to gas. @mr brown - the 'clicker' wasn't igniting the gas but used a lighter and instantly lit. Sounds like a gap issue? or spark a bit weak? (is a weak spark possible or is it more a matter of there/not there?)

weak spark is possible,can the electrode be moved nearer to the metal ? is electrode clean ?

 

[wildebus]

weak spark is possible,can the electrode be moved nearer to the metal ? is electrode clean ?

so what you reckon? some wet and dry on the electrode to shine it up a bit? move a touch closer - but best to adjust when it is hot or cold?

 

[mr brown]

just look at it now for a few clicks ,then move it a couple of mm nearer and see if it improves

 

[The Griffos]

sounds like your mother board is on its way out

We have the same problem. Motherboards in campervans didn't exist 25 years ago ......

 

[wildebus]

The auto selector can cause problems. I think there is a delay so that if you are on battery and pull in for fuel the gas does not spark up as soon as you switch the engine off.
We always use manual selection......................even then when changing source to gas we have to leave it switched off for a while.I guess the delay function still kicks in.
As said keep the burner area clean, but also we find it sometimes needs a rap on gas regulator or solenoid which can stick and stop the gas coming through when required.......trace the gas pipe back from the burner

Manual or Auto makes no difference. Even if on manual and gas, if the burner needs to relight if the thermostat calls for cooling and does not, then the fridge won't work.

The delay on a Thetford is only present on Auto and only then when switching from 12V to Gas. If switching from 12V to AC there is no delay and if switching from AC to Gas there is no delay. Other makes may be different of course.

We have the same problem. Motherboards in campervans didn't exist 25 years ago ......

I am certainly not a fridge expert but I fail to see how this is a motherboard failure? the gas is not lighting but all the right things are being sent by the motherboard for it to do so - the gas flow starts, the sparks are happening and all in the right sequence. And if I put a lighter in the burner, the gas lights.
I guess if there is a part that controls how strong the spark is, that could be faulty but I doubt it is that sophisticated and it will be simply "spark on", and not "spark on at x power"

 

[snapster]

Earlier you mentioned cleaning the jet out. I did mine, there was a tiny bit of crud partially blocking it. I took the jet off then blew through from the front with an aerosol air jet. Don’t poke anything in the hole!
A blocked jet will ( obviously) restrict gas flow and the fridge won’t cool properly. Mine would not cool below about 12 degrees last summer on gas ( 12v and mains were fine) After cleaning, the fridge ran perfectly and cooled down to 3 degrees or less.
A blocked jet may have some effect on lighting, but mine didn’t.

Just a thought, is there a separate battery for the spark igniter?

 

[wildebus]

main leisure battery for the igniter I am sure.
If the weather is kind tomorrow I will blow some air around the system and tweak the electrode position.

 

[wildebus]

Weather too variable to spend too long by vent to do a clean out.
I did however move the ignitor closer to the burner by a virtually imperceptible amount and it is now lighting on the first click (I don't even have time to press the button on the fridge and get outside to the vent before it is lit, so a massive difference )

So turned out to be a simple adjustment and I am sure those with gas fridges will be going "duh. obvious" but I'm a 3-way Newbie (maybe reword that phrase? ).
Thanks for the suggestions and advice of those who replied. Appreciated.


(and I do still need to check the fridge cools properly on Gas like it does on AC of course)

 

[Molly 3]

First thing to change is the jet .

 

[wildebus]

First thing to change is the jet .

depends if it works or not.

 

[Billy Ruffian]

depends if it works or not.

I have the same fridge and the same problem. Will get it fixed today.

 

[wildebus]

Something that would seem to be missing on mine is the cover over the burner? I would think this would allow some of the heat of the gas to escape and become less efficient so need to get something to put in place there I guess.
Fridge does seem to work - eventually now down to 3C from 7C around 12 hours ago, but appears to take about 2 hours per 1C drop, so hardly a fast operator on Gas! on AC it seems to take around 45 Minutes per 1C drop. Is it typical for 3-Ways to be slower to cool on Gas than AC? (I know on DC they are very poor but thought AC and Gas were the same apart from fuel source?)

 

[mr brown]

usually best on gas . maybe the jet does need a clean

 

[LT Man]

In my experience with a similar fridge which I still have my guess it is not enough voltage getting to the gas valve .
It need from memory 1v and mine wes only getting 0.85 which was just not enough for it to open .
Hence the 15 seconds of sparking then it automatically gives up..
Try cleaning the connections to the gas valve and also make sure the pins on the harness are getting a good connection .
I have to run mine with a cable tidy and a bit of foam jammed in a position to keep it pushed tight in one position to keep it working..

If it ever just starts kicking as you mentioned i just take the vent off and push the side of the harness plug and hey presto it fires so just have to add foam to tighten my cable tidy. That is how i know at least causes this issue on my fridge and been like that for three years .

Before I worked out myself what was causing this problem a dealer ( not naming but I do not trust any ) said the fridge had to be changed completely as not repairable. I did not even ask cost and just drove away.

Hope that helps


LT Man

 

[maingate]

In my experience with a similar fridge which I still have my guess it is not enough voltage getting to the gas valve .
It need from memory 1v and mine wes only getting 0.85 which was just not enough for it to open .
Hence the 15 seconds of sparking then it automatically gives up..
Try cleaning the connections to the gas valve and also make sure the pins on the harness are getting a good connection .
I have to run mine with a cable tidy and a bit of foam jammed in a position to keep it pushed tight in one position to keep it working..

If it ever just starts kicking as you mentioned i just take the vent off and push the side of the harness plug and hey presto it fires so just have to add foam to tighten my cable tidy. That is how i know at least causes this issue on my fridge and been like that for three years .

Before I worked out myself what was causing this problem a dealer ( not naming but I do not trust any ) said the fridge had to be changed completely as not repairable. I did not even ask cost and just drove away.

Hope that helps


LT Man

Had the same advice from a Dealer. Not repairable, they even said they had contacted Dometic Technical for advice who agreed it was knackered completely. The cost was £2,350 for a new one and £150 for installation.

I took it home, cleaned the Flue, the Jet and the Burner. Everything has been fine for the last 3 years.

 

[wildebus]

Had the same advice from a Dealer. Not repairable, they even said they had contacted Dometic Technical for advice who agreed it was knackered completely. The cost was £2,350 for a new one and £150 for installation.

I took it home, cleaned the Flue, the Jet and the Burner. Everything has been fine for the last 3 years.

I bet they would have offered to sell you a used one for £1600 (which would have been the unrepairable one they took out for the last guy)!

 

[in-it-for-fun]

I have very little experience with gas!!!! but there is little danger if you use a vaccum cleaner around the gas burner and the spark. there may be debris that could "short" the spark reducing it's effectiveness. Take care not to actually touch the gas mantle or the spark as this will be dangerious.
health and safety of course but adults with common sense will take sufficient care with gas and electric. Turn the gas off ofcourse and release the gas via the cooker.