Unusual Thetford fridge issue

[Winstanley]

First post so please be gentle !!

But if you like a challenge read on.

I have a new to me, 12 months ago, Autotrail Tracker fixed bed on a 2013 Fiat Ducato.

It has fitted a Thetford N3175 AES three way fridge which works fine on mains and gas. However it does not work on 12 volt. Fridge / Freezer chilled down on mains to roughly + 2 fridge and - 15 freezer. After travelling for more than an hour the fridge is +8 or more, freezer is around zero. This is the same on every journey.

It has been back to the dealer about six times and so far has had every electrical component on the fridge replaced including two new 12 volt elements. The EM40 unit has been replaced together with the wiring from it directly to the fridge. Vehicle alternator, battery and leisure battery checked and all fine.

On the last visit to the dealer they changed the 12 volt element again, chilled it on mains then ran on tick over for two hours and temperature steady at -12 and + 3. Vehicle driven for an hour or so and fridge / freezer heats back up again.

My dealer, who I cannot fault and who have gone well above and beyond what I would expect have sought technical advice from Thetford and Autotrail neither of whom seem to have a solution.

Any thoughts would be greatly appreciated.

 

[fishplug]

My first thought would be to reject the current fridge as 'not fit for purpose' and get a replacement unit.

If that does the same thing then I'd start to suspect some external factor as it's unlikely to have two fridges fail.

Assuming you don't already have one, it might be worth putting in a regulator for the 12v supply as well.

 

[stevewagner]

Running an engine on tick over for two hours can do more harm than good

 

[Winstanley]

My first thought would be to reject the current fridge as 'not fit for purpose' and get a replacement unit.

If that does the same thing then I'd start to suspect some external factor as it's unlikely to have two fridges fail.

Assuming you don't already have one, it might be worth putting in a regulator for the 12v supply as well.

A replacement fridge was my next thought, up until now both Thetford and Autotrail have been adamant it can’t be the fridge as every component has been replaced. But I’m going to request that now - thanks

 

[GeoffnDee]

Is there not an error code showing on the right of the display if it is LCD or through the service mode if it is a LED display . If no error code did the items replaced include the power board ?
Has the D+ signal connection been checked at the Fiat Motorhome converters connection in the B pillar and has anyone checked the Fiat BCM for a possible D+ signal fault .

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[fishplug]

A replacement fridge was my next thought, up until now both Thetford and Autotrail have been adamant it can’t be the fridge as every component has been replaced. But I’m going to request that now - thanks

My experience of these sorts of things is that there's probably something that's been overlooked or missed somewhere and sometimes you just need to bypass the repair.

We had a conservatory installed some years back and the roof always leaked. It was repaired, parts replaced many times over and always leaked. Specialists came from Scotland (I'm in Cambridge) and they said it must be condensation and started to turn around and go home until I insisted they stayed while I put the hosepipe onto it.... Oh, yeah, that's a leak....

This went on for years with the fitters blaming the manufacturers and vice versa. Different silicones were used, long cure, short cure - the lot. Eventually the guy from the fitters left the company and his replacement said he wanted to come and have a look. He brought the guys who had done the fitting and repairs many times over (I knew how they took their tea by this point). I thought it was pointless, but in his shoes I'd be doing the same so agreed to the visit.

Two seconds it took him. He looked up and said "why has that junction bar been put in upside down?"....

A replacement unit will prove it one way or the other. If the new one works then there was something not right with the old one. If the new one doesn't work then the problem lies elsewhere. I can only think it would be the 12v supply somehow. Possibly unregulated voltage spiking in a way the fridge doesn't like, or maybe just as simple as insufficiently thick cabling causing voltage drop so the fridge isn't getting the power it needs.

 

[Winstanley]

Is there not an error code showing on the right of the display if it is LCD or through the service mode if it is a LED display . If no error code did the items replaced include the power board ?
Has the D+ signal connection been checked at the Fiat Motorhome converters connection in the B pillar and has anyone checked the Fiat BCM for a possible D+ signal fault .

Never had an error code showing, Thetford advise you can get poor cooling with no error code. Electrics all checked from vehicle battery, via new EM41 and new cabling to fridge. Thanks

 

[Winstanley]

My experience of these sorts of things is that there's probably something that's been overlooked or missed somewhere and sometimes you just need to bypass the repair.

We had a conservatory installed some years back and the roof always leaked. It was repaired, parts replaced many times over and always leaked. Specialists came from Scotland (I'm in Cambridge) and they said it must be condensation and started to turn around and go home until I insisted they stayed while I put the hosepipe onto it.... Oh, yeah, that's a leak....

This went on for years with the fitters blaming the manufacturers and vice versa. Different silicones were used, long cure, short cure - the lot. Eventually the guy from the fitters left the company and his replacement said he wanted to come and have a look. He brought the guys who had done the fitting and repairs many times over (I knew how they took their tea by this point). I thought it was pointless, but in his shoes I'd be doing the same so agreed to the visit.

Two seconds it took him. He looked up and said "why has that junction bar been put in upside down?"....

A replacement unit will prove it one way or the other. If the new one works then there was something not right with the old one. If the new one doesn't work then the problem lies elsewhere. I can only think it would be the 12v supply somehow. Possibly unregulated voltage spiking in a way the fridge doesn't like, or maybe just as simple as insufficiently thick cabling causing voltage drop so the fridge isn't getting the power it needs.

Glad I don’t have a conservatory !!
Going to push for a new fridge and see where we go. Wiring from new EM41 replaced with specific thickness cable recommended by Thetford. Thanks

 

[GeoffnDee]

Poor cooling without a fault code can be a faulty fridge power board , but I take it that it has been replaced . As the wiring from the starter battery and EM41 has been checked/replaced It could be that the wiring and connections going to the EM41 via the Fiat BCM and the converters socket also need checking ( For problems with the D+ signal required for 12v fridge cooling operation ).

 

[Winstanley]

Poor cooling without a fault code can be a faulty fridge power board , but I take it that it has been replaced . As the wiring from the EM41 has been checked/replaced It could be that the wiring and connections going to the EM41 via the Fiat BCM and the converters socket also need checking ( For problems with the D+ signal for 12v fridge cooling operation ).

Hi, any idea at all where the BCM and converter socket would be on mine - Thanks

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[GeoffnDee]

The converters socket should be behind the drivers seat in the base of the Drivers side B pillar behind a cover and the BCM (Body Control Module) is part of the Fiat dash fuse box assembly ( It needs a code reader to check for faults)

 

[Barriesimpson]

These fridges do not cool while working on 12v, they 'maintain' the actual temperature. I had a problem with ours as in the door was not closing properly at the bottom, so while driving the cold was escaping. I suggest you check the proper closing of the door and that it is sealing completely, you will easily see if it is not. I now push the bottom of the door completely closed after taking out or putting in anything.

 

[jockaneezer]

It does sound more "electronic" than "electrical" if you get my drift, you can't get much simpler than the 12 volt heating element, but the stuff that tells it what to do is another story !
A quick check of the door as Barrie suggests would be to shut a strip of paper in the door and see if it will pull out when the door is closed, trying top and bottom and hinge and lock side seperately, but I'm guessing it it gets cold enough on the other power sources, the door may be ok ?

 

[Burge]

Ours was defrosting on Engine Running had 14.2 v at Fridge so Techie said Control Board is faulty, had that replaced under Warranty ,bin good up to now.

 

[Barriesimpson]

A quick check of the door as Barrie suggests would be to shut a strip of paper in the door and see if it will pull out when the door is closed, trying top and bottom and hinge and lock side seperately, but I'm guessing it it gets cold enough on the other power sources, the door may be ok ?

The difference being that on gas and/or 230v the system will keep running and trying to maintain the set temperature whereas on 12v it won't.

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[Cheese Monster]

We have a Thetford N3150 fridge freezer. Since it was 2 years old it has had times when it becomes an oven, the freezer gets to 14°C! This happens on all three power sources. The only cure is to switch it off for 2 hours so it can cool and then it will work OK.

One rally there was 5 of us with the same fridge all with the symptoms.

In the next weeks it will be changed for a 12v compressor fridge.