Thetford fridge - not working!

[2dandaddy]

Hi -
Help! My fridge is not working! Had it working on 240 volts at home on drive! Travelled to Grantown on Spey from near Edinburgh and found fridge led was flashing! When I checked Hymer manual found that this could be lack of energy source so changed it gas whack I knew was fully charged! Seemed to accept change of energy to gas but started flashing again! I’ve changed the batteries in the compartment- 6 AA batteries- and again thought that I had fixed it but after a few minutes reverted to flashing again! Now the freezer is dirge and freezer is not working and I think I’m going to have to go home to try and fix problem! Any ideas gratefully accepted!

 

[IRHP]

The N3142 has 2 x12v supplies high and low current. If the controls are lit your 12v low current is fine. If it's running on 12v when the engine is on your High current is fine so forget relays or fuses. Mine doesn't have a relay as the 12v high current is always live. The D+ signal from the alternator is fed into the fridge PCB and this tells it to run on 12v when the engine is running. It sounds like you have no gas or an ignition problem. Hearing the clicks sounds like the ignition is ok. Can you smell gas coming through at the inspect point behind the rear vent? Perhaps the gas valve isn't opening? Power feed to PCB in the attached pic.

 

[GeoffnDee]

You could try checking the wiring connections at the gas valve solenoid and burner control module

 

[2dandaddy]

The N3142 has 2 x12v supplies high and low current. If the controls are lit your 12v low current is fine. If it's running on 12v when the engine is on your High current is fine so forget relays or fuses. Mine doesn't have a relay as the 12v high current is always live. The D+ signal from the alternator is fed into the fridge PCB and this tells it to run on 12v when the engine is running. It sounds like you have no gas or an ignition problem. Hearing the clicks sounds like the ignition is ok. Can you smell gas coming through at the inspect point behind the rear vent? Perhaps the gas valve isn't opening? Power feed to PCB in the attached pic.



View attachment 878865

Hi - Heating working, hob working and oven working all on gas! Fridge working on gas when engine is on! Is there some sort of solenoid control that controls gas flow when on 12 volts and engine off?

 

[Lenny HB]

Hi - Heating working, hob working and oven working all on gas! Fridge working on gas when engine is on! Is there some sort of solenoid control that controls gas flow when on 12 volts and engine off?

Sounds like a control problem gas solenoid on the fridge should be off with the engine running.

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[2dandaddy]

The N3142 has 2 x12v supplies high and low current. If the controls are lit your 12v low current is fine. If it's running on 12v when the engine is on your High current is fine so forget relays or fuses. Mine doesn't have a relay as the 12v high current is always live. The D+ signal from the alternator is fed into the fridge PCB and this tells it to run on 12v when the engine is running. It sounds like you have no gas or an ignition problem. Hearing the clicks sounds like the ignition is ok. Can you smell gas coming through at the inspect point behind the rear vent? Perhaps the gas valve isn't opening? Power feed to PCB in the attached pic.



View attachment 878865

Hi - do you mean the bottom outside cover for fridge? There’s a valve in the gas pipe there with an electrical connection to it! There’s also an inspection plate where you can see the piezo igniter sparking away! I’d imagine there should be gas there!?

 

[2dandaddy]

Sounds like a control problem gas solenoid on the fridge should be off with the engine running.

Hi Lenny- so does that mean that the feed to this valve should be live when running on gas?

 

[Lenny HB]

Hi Lenny- so does that mean that the feed to this valve should be live when running on gas?

Yes.

 

[Eyeballmike]

 

[Eyeballmike]

Sounds to me like it's the gas valve and/or the wire to it from the control module.

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[Eyeballmike]

But you do need to check that it is actually sparking? Is it..? There is a cover plate with a viewing hole that slides, or remove the whole metal cover

 

[autorouter]

There are two separate 12V supplies to a 3-way fridge. One is a low current (LC) supply, usually from the leisure battery, and powers the fridge control board, gas valve and ignition etc. It is on all the time, and switches the fridge between 240V, gas and 12V power. The other is the high current (HC) supply, usually from the starter batter/alternator, and is only on while the engine is running. and powers the 12V heating element.

If you can hear the gas igniter clicking as it sparks when switched to gas, then the 12V LC is working. There's a few more things need to happen for the gas to work. The gas valve needs to switch on to allow the gas, the igniter needs to ignite the gas so there's a flame, the flame failure detector needs to register that the flame is present, and only then will the gas glow properly to cool the fridge.

 

[2dandaddy]

Hi Lenny- so does that mean that the feed to this valve should be live when running on gas?

But you do need to check that it is actually sparking? Is it..? There is a cover plate with a viewing hole that slides, or remove the whole metal cover

Hi - yep! Slid the cover over and can see spark! When sparking there is a faint whiff of gas and a few pops from what I presume to be the burner but nothing continuous! Tried to take electrical connection off gas solenoid but the spark stopped working! Screwed it back in and spark started to work again! Could the valve be sticking! Tried the obvious( gave it a tap several times) but still nothing!

 

[2dandaddy]

There are two separate 12V supplies to a 3-way fridge. One is a low current (LC) supply, usually from the leisure battery, and powers the fridge control board, gas valve and ignition etc. It is on all the time, and switches the fridge between 240V, gas and 12V power. The other is the high current (HC) supply, usually from the starter batter/alternator, and is only on while the engine is running. and powers the 12V heating element.

If you can hear the gas igniter clicking as it sparks when switched to gas, then the 12V LC is working. There's a few more things need to happen for the gas to work. The gas valve needs to switch on to allow the gas, the igniter needs to ignite the gas so there's a flame, the flame failure detector needs to register that the flame is present, and only then will the gas glow properly to cool the fridge.

That helps! There is definetly a faint whiff of gas when sparking and a few pops of flame but nothing after that! Could this be a control box failure to turn on main gas flow and how would it do this?

 

[autorouter]

It could be the gas valve not turning on fully, but if you're getting a whiff of gas then that's a good sign. Could it be the gas jet blocked, maybe partially. Either from rust particles from inside the gas pipe, or soot/debris falling from the flue?

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[Clive Beeza]

It could be the gas valve not turning on fully, but if you're getting a whiff of gas then that;s a good sign. Could it be the gas jet blocked, maybe partially. Either from rust particles from inside the gas pipe, or soot/debris falling from the flue?

That is exactly what caused a similar issue on our van
rust/dust particles fallen down from the flue stack
and interfering with the gas flow from the jet

 

[KiwiKampers]

That is exactly what caused a similar issue on our van
rust/dust particles fallen down from the flue stack
and interfering with the gas flow from the jet

I agree with Clive Beeza. Try cleaning the jet. I was told you should clean the jet at least once a year. We drive on gravel roads a lot and it’s amazing how much dust gathers in there.

 

[IRHP]

Hi - do you mean the bottom outside cover for fridge? There’s a valve in the gas pipe there with an electrical connection to it! There’s also an inspection plate where you can see the piezo igniter sparking away! I’d imagine there should be gas there!?

Yes and yes

 

[2dandaddy]

There are two separate 12V supplies to a 3-way fridge. One is a low current (LC) supply, usually from the leisure battery, and powers the fridge control board, gas valve and ignition etc. It is on all the time, and switches the fridge between 240V, gas and 12V power. The other is the high current (HC) supply, usually from the starter batter/alternator, and is only on while the engine is running. and powers the 12V heating element.

If you can hear the gas igniter clicking as it sparks when switched to gas, then the 12V LC is working. There's a few more things need to happen for the gas to work. The gas valve needs to switch on to allow the gas, the igniter needs to ignite the gas so there's a flame, the flame failure detector needs to register that the flame is present, and only then will the gas glow properly to cool the fridge.

Hi auto router - that makes a lot of sense! Finished for the day but will try going back to gas operation with the engine running to see if control unit switches gas valve to main flow! If it does then to my thinking that leaves wire to control unit or control unit!?!? How does the sensor for flame failure work?

 

[autorouter]

I get the impression that it's not an electrical problem, and it's the gas that's not working. Since it's an automatic fridge with no manual selection, if you want to get the gas working you should avoid starting the engine. When the engine starts it goes to 12V power from the alternator/starter battery, and disables the gas. The gas won't work for about 15 minutes after you stop the engine.

The flame failure sensor is not really relevant here. When the gas valve turns on and the igniter starts sparking, the sparking continues for about 30 seconds, and in that time the flame failure sensor won't cut off the gas. After that 30 seconds, the igniter stops sparking, and at that point if the flame detector can't detect a flame, the gas supply is cut off.

If the flame failure sensor was faulty, you would see a healthy flame for a few seconds, that stops as soon as the sparking stops. That's not what happens, so it's not a flame detector problem.

I think the problem is around the gas burner, they commonly need to have the gas jet hole unblocked and cleaned.

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[wiff2110]

similar problem, even replaced the fridge but the intermittent problem didn’t go away. Finally replaced the gas solenoid that is fed from the gas bottle, it was gummed up internally. Replacement fixed my problem (would have been much cheaper than the fridge)

 

[2dandaddy]

I get the impression that it's not an electrical problem, and it's the gas that's not working. Since it's an automatic fridge with no manual selection, if you want to get the gas working you should avoid starting the engine. When the engine starts it goes to 12V power from the alternator/starter battery, and disables the gas. The gas won't work for about 15 minutes after you stop the engine.

The flame failure sensor is not really relevant here. When the gas valve turns on and the igniter starts sparking, the sparking continues for about 30 seconds, and in that time the flame failure sensor won't cut off the gas. After that 30 seconds, the igniter stops sparking, and at that point if the flame detector can't detect a flame, the gas supply is cut off.

If the flame failure sensor was faulty, you would see a healthy flame for a few seconds, that stops as soon as the sparking stops. That's not what happens, so it's not a flame detector problem.

I think the problem is around the gas burner, they commonly need to have the gas jet hole unblocked and cleaned.

Think you’re right! Got the burner out but looks clean! Appears to be a tiny hole at end which I presume to be a jet! Can’t blow through it and don’t want to prod it with anything! I’d imagine there might be nozzle cleaners but not sure where I’d get them! Any ideas?!

 

[dawsey]

Faraway- hi - no cover! Haven’t touched the cover! Did wash the Motorhome before I left previous day?!?!

This might be your problem. If water gets into the void where the burner is it can affect the ionisation sensor making the light flash. Put the vent in full sun with the heating on and the fridge powered by mains for 48hr to let it dry out.

 

[autorouter]

Appears to be a tiny hole at end which I presume to be a jet! Can’t blow through it and don’t want to prod it with anything! I’d imagine there might be nozzle cleaners but not sure where I’d get them! Any ideas?!

I'm sure others have more idea than me, but I would try blowing air through it - a bicycle pump or a tyre compressor maybe. You are right to be cautious about prodding it, it's brass so it's softer than steel and easily damaged. I'd try a thin strand of copper, from a multistrand cable. Or maybe a bristle from a brass wire brush. I presume the correct tool is available from gas specialists, and probably the size is stamped on the jet somewhere.

 

[KiwiKampers]

I am going to suggest you check the obvious.
1. Are you parked on level ground.
2. When was the last time you cleaned the gas jet?
Our Thetford fridge/freezer flashes an LED with a spanner symbol and a number to indicate what the problem is. I'm assuming yours doesn't do that?

I’m not going to say, “I told you so” … but now that you have discovered you need to clean the jet you need to find an appropriate sized piece of wire and poke it into the hole. Job done!

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[2dandaddy]

I'm sure others have more idea than me, but I would try blowing air through it - a bicycle pump or a tyre compressor maybe. You are right to be cautious about prodding it, it's brass so it's softer than steel and easily damaged. I'd try a thin strand of copper, from a multistrand cable. Or maybe a bristle from a brass wire brush. I presume the correct tool is available from gas specialists, and probably the size is stamped on the jet somewhere.

Cheers Autorouter- can’t get into the actual jet and don’t want to fiddle too much with burner unit! Used to strip carbs in a previous life so know about damaging the orifice! Might try a piece of copper strand though if I can find a bit thin enough and strong enough! Thinking solenoid valve may be partially stuck! Wondering if I turn off gas valve under galley unit that I can remove the solenoid valve to get a closer look at it! What do you think??

 

[2dandaddy]

I’m not going to say, “I told you so” … but now that you have discovered you need to clean the jet you need to find an appropriate sized piece of wire and poke it into the hole. Job done!

Thanks Kiwicamper- thank goodness you didn’t say ‘ I told you so’!!! Thanks for you’re input - appreciated!

 

[2dandaddy]

Hi -
Help! My fridge is not working! Had it working on 240 volts at home on drive! Travelled to Grantown on Spey from near Edinburgh and found fridge led was flashing! When I checked Hymer manual found that this could be lack of energy source so changed it gas whack I knew was fully charged! Seemed to accept change of energy to gas but started flashing again! I’ve changed the batteries in the compartment- 6 AA batteries- and again thought that I had fixed it but after a few minutes reverted to flashing again! Now the freezer is dirge and freezer is not working and I think I’m going to have to go home to try and fix problem! Any ideas gratefully accepted!

Hi people- not sure how this works but hope that everybody who had an input can read this!
Found the fault - gas burner was partly clogged though it looked perfectly clean! Managed to get jet out of burner and squirted water through it from a syringe with the assistance of repair team at Knowepark Livingston - many thanks to them! Cleaned jet replaced roughly to check operation and worked fine! Appears that piezo igniter is also a thermocouple which tells the control unit there is a flame and to keep gas solenoid open! Just need to box things back up again and retry!
Really appreciate the help from all especially Autorouter and Lenny This a really useful forum with knowledgeable members and kind hearts! Thanks again!

 

[autorouter]

Appears that piezo igniter is also a thermocouple which tells the control unit there is a flame and to keep gas solenoid open!

Great to hear that you got it working

That's more or less correct, but slightly wrong technology. The igniter is a high voltage induction coil, not a piezo igniter. The flame detector is a resistive sensor, not a thermocouple. When the coil current is turned on and off, a stream of sparks is generated. It's similar to a petrol engine induction coil that feeds the spark plugs.

A piezo-electric spark generator is different. If you give a quartz crystal a jolly good whack (technical term) it generates a very high voltage across its faces. This can be used to generate a spark. But it's the old style method, where you press a button and there's a loud click and a spark. One spark per press. Piezo sparkers are commonly used to light gas flames, but not in this case.

The flame detector is a resistance sensor. It has two metal electrodes. If there is ordinary air or non-burning gas between the electrodes, the resistance is very high, and no current will flow. If there is a burning flame between the electrodes, the ionised gas of the flame conducts electricity, so a small current will flow. The control board detects this current, and registers that a flame is present.

A thermocouple works in a different way. When the junction between two metals is heated, it generates a very small voltage. The control board can detect this voltage to register that a flame is present. Thermocouples are commonly used as flame detectors, but not in this case.

 

[2dandaddy]

Great to hear that you got it working

That's more or less correct, but slightly wrong technology. The igniter is a high voltage induction coil, not a piezo igniter. The flame detector is a resistive sensor, not a thermocouple. When the coil current is turned on and off, a stream of sparks is generated. It's similar to a petrol engine induction coil that feeds the spark plugs.

A piezo-electric spark generator is different. If you give a quartz crystal a jolly good whack (technical term) it generates a very high voltage across its faces. This can be used to generate a spark. But it's the old style method, where you press a button and there's a loud click and a spark. One spark per press. Piezo sparkers are commonly used to light gas flames, but not in this case.

The flame detector is a resistance sensor. It has two metal electrodes. If there is ordinary air or non-burning gas between the electrodes, the resistance is very high, and no current will flow. If there is a burning flame between the electrodes, the ionised gas of the flame conducts electricity, so a small current will flow. The control board detects this current, and registers that a flame is present.

A thermocouple works in a different way. When the junction between two metals is heated, it generates a very small voltage. The control board can detect this voltage to register that a flame is present. Thermocouples are commonly used as flame detectors, but not in this case.

Hi Autorouter- Every days a school day!! As I said there are some very knowledgeable and helpful people in this club! Thanks again!