Motorhome Thetford 3-way Fridge Fault, Help

@Hop3
Does your fridge require you to manually start the gas by holding a button in?
If so you may have a dodgy thermocouple or the flame is marginal.
Have you looked at the flame to check that it's a decent size and heats the flame failure device/thermocouple?
 
I will check the size of the flame in the morning. And clean the end of the probe.
The fridge is automatic- or set manually by scrolling through 12v, mains or gas.
When gas is chosen it starts clicking and the burner ignites. The issue is that the clicking does not stop even if the burner is running.
After a time, about 15 seconds, the gas is turned off.
It has happened before, but perseverance worked. Not this time though.
 
Having woken early I've done a bit of web research and it would seem that this fridge is automatic energy selection.
YouTube videos show that it has solenoid gas valve and uses ionization flame failure detection to hold the valve open.
As it will light the valve must be ok.
So the flame detection is under par.
Check to ensure that the probe is in the flame and that it's the correct distance from the casing.
It might benefit from being cleaned with gentle abrasive.
 
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Hop3 said:
Hi
I have just joined the thread.I have a Thetford N175 3 way fridge.. After the winter the gas will not start. Similar to above threads,
clicks for 15 seconds approx, gas runs , then closes down.
I did get it running for about 1/2 hr, but is went out while my back was turned.
I took the fridge out, cleaned the burner and flue,, soaked the jet in a cleaning fluid, but the same result.
The fridge is 9 yrs old, but is very clean with little use on gas.
Any help would be appreciated. In NZ, no thetford fridge agents listed.
Click to expand...
Could be the Gas control valve !
Described as the exact problem we had ..Starts but then stops
Starts because the valve opens initially..then closes because the valve if faulty
IF this is the case i recommend a replacement gas valve.
My fridge is Dometic not thetford !
 
Hop3 said:
I will check the size of the flame in the morning. And clean the end of the probe.
The fridge is automatic- or set manually by scrolling through 12v, mains or gas.
When gas is chosen it starts clicking and the burner ignites. The issue is that the clicking does not stop even if the burner is running.
After a time, about 15 seconds, the gas is turned off.
It has happened before, but perseverance worked. Not this time though.
Click to expand...
So what you have is the ionization flame sensor not passing enough current to keep the valve open but as you do get ignition my initial reaction is that the valve itself is obviously ok.
The flame sensor issue could be positioning - either not in flame or correct distance from 'earth' which you can check/adjust.
Or it could be the 'electronics' at the control end.
It's a combined ignitor probe & sensor so whilst the voltage/current for the spark to get through is enough to surmount a bad connection the ionization current is very small so it's possible that a poor connection might be a issue.
Just taking it off or wiggling it may do the trick?

However Jagmanx has had a problem with the valve opening initially but not staying open suggesting two separate feeds to the solenoid.
If there are two then you can check whether there is voltage to both and at which time.
No volts on second phase points the finger at control unit.

On the older manual fridges this was self contained and all it did was turn off the spark when ionization worked, gas flow being controlled by the thermocouple. However with a solenoid valve there has to be some electronic switch maintaining current to hold it open after the initial 15 second start period.

As a matter of interest what fault code do you get?
I note that nearly all the actions in the check list are 'see a dealer' but it might be interesting to know what the system says.

Try this video for tips - pity he didn't have the torch he recommended using 😀

 
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hi i fixed ops original fault it was showing fault 9 i changed the flame sensing device and all is good now
 
Hop3 said:
Hi
I have just joined the thread.I have a Thetford N175 3 way fridge.. After the winter the gas will not start. Similar to above threads,
clicks for 15 seconds approx, gas runs , then closes down.
I did get it running for about 1/2 hr, but is went out while my back was turned.
I took the fridge out, cleaned the burner and flue,, soaked the jet in a cleaning fluid, but the same result.
The fridge is 9 yrs old, but is very clean with little use on gas.
Any help would be appreciated. In NZ, no thetford fridge agents listed.
Click to expand...
Hi Hop,

Sometimes after a long break items like thermocouples can be a problem. They work due to a low voltage/ low current being produced by the hot flame. If you are sure the thermocouple is in the flame correctly, try removing and refitting the spade connector on the thermocouple a couple of times. It can be as simple as that sometimes
 
The ionisation current is very low so it's susceptible to any resistance in the circuit.
So cleaning all the spade connections is a good idea - pulling off and wiggling often do the trick.
If you have a mechanical mode selection switch this too can often be a 'weak link' in the circuit in terms of turning off the spark.
My older fridge freezer would continue to burn after initial ignition because of capillary bulb holding gas open but would continue to 'spark'.
Cleaning the 'blades' in the multi way selector switch did the trick.
In this case it's all electronic so if the controller doesn't see 'perfect' conditions it shuts down.
There's probably nothing 'broken' so a bit of patience checking the circuit and making sure the probe is in the hot zone just above the flame should get it going.

There's a lot to be said for upping leisure battery and solar then going for a compressor fridge if anything major is needed.
 
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