Thetford N100 fridge not working on 12V Error Code 10

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Richard Hill

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Hi All,
Another fridge question!
Our Thetford N100 fridge is not working on 12V (with engine running) and is displaying Error Code 10.
I have accessed the wiring to the power board through the exterior lower vent and found that when the engine is running I'm only getting 1V across the HC 12V connection, but if I disconnect these wires I measure over 12V on them as expected.
Before I dismantle this any further would anyone be able to confirm from this what the issue is?
Cheers,
Rich
 
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Not sure where the supply comes from on a Hymer but our AutoTrail has repeated problems with the supply to the DC elements which comes from the Sargent EM40 fuse box we have fitted. This supply only comes on when the engine is running.
 
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Thanks Wombles and Iain.

The supply gets onto the power board at the back of the fridge but only measures 1 Volt when the wires are connected to the power board, but measures over 12V (as expected) if I remove them, so I think the problem might be with the power board or the DC element pulling the voltage down? or is there a relay involved in the supply which might have a poor connection?
 
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My guess would be the Element. If you disconnect the wires at the power board and measure the resistance that should confirm it or otherwise. I think a good element is around 50ohms.

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Richard Hill Is it possible that there is not a D+ signal going to the fridge with the engine running , if it is not , the heater element would not power up. The HC would be going to the power board ,if that is where you are checking it , but not being switched to the power board supply side to the element if the D+ is not present.
 
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iain26 said:
My guess would be the Element. If you disconnect the wires at the power board and measure the resistance that should confirm it or otherwise. I think a good element is around 50ohms.
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I'd check the element first too. I think the resistance is very low, more like 1 ohm. A 96W element would have a resistance of 1.5 ohms.

That is difficult to measure accurately with a cheap multimeter, they usually have a lowest range of 200 ohms. Try touching the probes together, see what the reading is, then see how much it changes when you probe the element
 
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GeoffnDee said:
Richard Hill Is it possible that there is not a D+ signal going to the fridge with the engine running , if it is not , the heater element would not power up. The HC would be going to the power board ,if that is where you are checking it , but not being switched to the power board supply side to the element if the D+ is not present.
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Thanks Geoff, but on this vehicle the D+ signal is linked across to the +ve HC connection rather than being a separate signal.
 
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autorouter said:
I'd check the element first too. I think the resistance is very low, more like 1 ohm. A 96W element would have a resistance of 1.5 ohms.

That is difficult to measure accurately with a cheap multimeter, they usually have a lowest range of 200 ohms. Try touching the probes together, see what the reading is, then see how much it changes when you probe the element
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Many thanks for the clarification.

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Hi All,
I've checked the element now and it measured 1.2 ohms so I think that is OK.
All of the fuses on the power board were also OK.
I'm starting to think the problem may be with high resistance in the 12V HC supply. The 20A fuse near the battery is OK, but does anyone know where this 20A fuse is fed from? (the base vehicle is a 2007 Ford Transit MK7 and the engine battery and the 20A fuse are under the driver seat).
Cheers,
Rich
 
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Yes, it did work before the problem started, we've always used it on 12V battery whilst travelling for about the past 5 years.
The full model number is N100 - N31G02L6E.
The type is C11 02 1032
 
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Is there a Schaudt EBL unit fitted that controls the supply from it to the 12v HC at the fridge ,if so , could there be a problem with connections at the EBL or at a connection joint that may be between them ?
 
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Yes, I think that's where I'm going to look next - have dug out the documentation for the Schaudt EBL 99 G which is located under the passenger seat and I understand that this also includes the split charge relay for the fridge HC 12V, but as you say might just hopefully be a connection issue.

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Check the wiring out of the back of the EBL for discolouration. I have seen several that have overheated because of a bad connection, so cooking the socket
 
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Thanks, everyone - will hopefully be able to look at this later in the week and will keep you posted.
 
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If it's an EBL99, the fridge element (HC) supply goes via quite a convoluted route, but it's possible to check the various sections.

The wire from the starter battery (with the 20A fuse, not the 50A) goes to Pin1 of the 5-way connector (Block2). That is on permanently, not just when the engine is running.

When the engine is running, the fridge relay should switch that 20A supply to either Pin1 or Pin4 of the 4-way connector (Block 1). There are no fuses in that bit of wiring inside the EBL, so it either works or it doesn't.

The D+ signal, which controls the fridge relay, comes in on Pin3 of the 5-way connector. If it's not working there is a 2A fuse for it, which I guess is near the 20A fuse next to the starter battery. The D+ signal goes out to the fridge on Pin2 of the 4-wayconnector.

From Pin1/4 of the 4-way connector, the supply goes straight to the HC connection of the fridge.

Which supply pin does it use on the 4-way, Pin1 or Pin4? The reason I ask is that, if it's Pin4, there's another test you can do. If you insert a 20A fuse in the 'Kompr/AES Kuhlschrank' slot, the supply to Pin4 switches to the leisure battery when the engine stops, so you can use that fact to test the wiring. It's meant for compressor fridges that don't work off gas, but it's useful as a test of the wiring.

The EBL 99 manual is available in the Resources section, or from the Schaudt website.
 
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That's really helpful Autorouter - many thanks.

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Finally had a chance to look at this a bit more and remove the passenger seat as the Schaudt EBL 99 G is under there with one of the leisure batteries.

Pin 1, Block 2 (starter battery) measures12V.
Pin 3, Block 2 (D+) measures 12V.
With the engine running Pin 1, Block 1 measures only 1.5V (I checked this with the connector removed), so I guess this ties up with what I see on the back of the fridge and maybe the problem is in the EBL?

Just prior to this I noticed that the fridge would no longer turn on at all (was previously working on 240V) and when I checked the standard 12V connection at the back of the fridge now shows 0V - any idea where that is fed from? Could this also be an EBL problem or something else?

All other 12V functions; lights, step, water, etc work OK.
 
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There are two 12V supplies to the fridge. One is the High Current (HC) supply to the 12V element that comes from the alternator/starter battery while the engine is running. The other is a Low Current (LC) supply that comes from the leisure battery via the EBL. It is usually wired to Circuit1 or Circuit2 (labelled Kreis 1 and Kries 2). The LC supply powers the fridge control board, and is on all the time, usually stays on even when the main 12V control switch for all the 12V electrics is off.
Richard Hill said:
Just prior to this I noticed that the fridge would no longer turn on at all (was previously working on 240V) and when I checked the standard 12V connection at the back of the fridge now shows 0V - any idea where that is fed from? Could this also be an EBL problem or something else?
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When you say the standard 12V connection do you mean the LC supply?
Which pin on Block1 is the fridge element wired to, Pin1 or Pin4?
The other thing that uses the D+signal is the split charge relay, that connects the alternator/starter battery to the leisure battery when the engine is running so that the alternator can charge both batteries. Can you tell if the leisure battery is charging when the engine is running? The voltage should rise to over 13V. That would tell you if the D+ signal is working.

You can check the fridge relay by checking the resistance between Block2 Pin1 and Block1 Pin1 or 4. Before you check the resistance, pull out the 20A fuse near the starter battery, and unplug the hookup to ensure the mains charger is off. If the relay is OK, it should have lowresistance when the engine is running, and high resistance when stopped.
 
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Thanks Autorouter,
The element is wired to Pin 1 on Block 1, but that only measures 1.5V.
Pin 4 on Block 1 doesn't have any wire connected to it at all.
I'll have a look at the other points next.
 
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Yes, sorry, when I said standard 12V I was referring to the 12V LC supply, which during my investigation has dropped from 12V on all the time to 0V all the time. As far as I can tell on my vehicle this has been wired to be delivered from the EBL on Block 5, pins 4 and 10 and they measure 0V - the wires from these pins are labeled Kuhlrschrank Steuerung (Refrigerator Control).

The D+ signal increases from 0V without the engine running to 14.2V with the engine running and the Leisure Battery measures 13.9V with the engine running.

I checked the fridge relay as suggested and I got high resistance with both the engine off and running. I find it a bit odd that the HC on Pin 1, Block 1 measures 1.5V with the engine running, but I guess it depends on how the relay has failed in the EBL - would you conclude that the EBL is faulty?
 
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Richard Hill said:
I checked the fridge relay as suggested and I got high resistance with both the engine off and running. I find it a bit odd that the HC on Pin 1, Block 1 measures 1.5V with the engine running, but I guess it depends on how the relay has failed in the EBL - would you conclude that the EBL is faulty?
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There are actually two fridge relays in that model of EBL. One is connected to Pin1, the other to Pin4. You could check Pin4 voltage to see if the fault is only with the Pin1 relay or both relays. If it's OK on Pin4 you could maybe transfer the wire from Pin1.

The only difference between the two is that with the Pin4 relay it's possible to run the fridge element from the leisure battery if you insert the 20A fuse marked 'Kompr/AES Kuhlschrank'. So if you don't insert the fuse, there's no difference.

Removing and re-inserting the pin is possible, see this thread for how to do it, post #18
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Wiring additional sockets. Where do I connect?

I'm planning to fit an additional 240V socket, a USB socket and a 12V cigar lighter type socket. They will all be close to the battery, the Electroblock (EBL271), and to the mains consumer unit. What's the best place to connect each? 240V socket to the consumer unit? The other two via the...
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Firstly, I found that the 2A fuse for Reserve 4 (Block 5, pins 4 and 10) used for the 12V LC supply had blown, having replaced that the LC supply is back - I guess at some point I blew that probing around at the back of the fridge.

Yes, Block 1 Pin 4 is measuring 14.1 V with the engine running, so I could transfer the wire from Pin 1, but do you see any issue leaving a faulty relay in situ, particularly as I measure 1.5V on Pin 1 with the engine running?
 
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Richard Hill said:
Firstly, I found that the 2A fuse for Reserve 4 (Block 5, pins 4 and 10) used for the 12V LC supply had blown, having replaced that the LC supply is back - I guess at some point I blew that probing around at the back of the fridge.

Yes, Block 1 Pin 4 is measuring 14.1 V with the engine running, so I could transfer the wire from Pin 1, but do you see any issue leaving a faulty relay in situ, particularly as I measure 1.5V on Pin 1 with the engine running?
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If you look on ebay you might be able to get a new relay, sometimes the exact pin dimensions are given 👍

If you leave it in though it should be OK, but I'd be thinking about that wasted 50ma coil current 🥺😆
 
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Thanks Richard, I'm sort of hoping to 'resolve' this as per Autorouter's suggestion and avoid removing and dismantling the EBL, but elsewhere someone has made another couple of points:

1. To use Block 1 pin 4 I would need to remove the 20A AES fuse, which actually is present even though there is no wire connected to Block 1 pin 4 (as my fridge doesn't have AES mode). I think removing this fuse is probably correct?

2. Will the EBL relay and PCB tracks used by Block 1 pin 4 be up to delivering a current of 8 to 12 Amps whilst driving continuously? Wouldn't they have to do that if my fridge had AES mode, or is Pin 4 just providing an AES signal rather than 12V High Current?
 
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