Electroblok 100 / AES Fridge Problem

[Lizbiebrowne]

The Thetford AES N145 fridge on my Hymer works fine on gas and electricity but not on 12 V. I'm new to Hymer and the Electroblok device so trying to sort out what's going on is likely to be a voyage of discovery but it didn't take me long to find one problem depicted here.

There's a few things about this that concern/confuse me. Obviously there's the overheating on Pin 1 of Block 1 (which might be due to someone previously soldering another yellow wire onto the output yellow cable and completing the job with insulation tape). Then there's the absence of a cable coming out of Pin 2 which my diagram suggests should be carrying the D+ signal from the alternator and finally there's a cable in Pin 4 which my diagram suggests is for a Compressor not an Absorption fridge although it also mentions AES. Can anyone throw any light on what's happening here? I appreciate some of these may be down to my naivety around the EBL apart, of course, from the charring - something definitely not right there.

 

[autorouter]

I can't see what model number of EBL it is, but I'm guessing it's an EBL99. The fridge supply comes from either Pin1 or Pin4. The difference is that Pin4 also gets power from the leisure battery when the engine isn't running, but Pin1 just goes off. That power comes through the fuse labelled 'Kompr/AES Kuhlschrank) (Kuhlschrank - fridge), so if that fuse is removed Pin1 and Pin4 are identical.

The pins are running at their full design capacity of about 15A for a fridge element, so it doesn't take much of an imperfection to start the pin heating. As it gets hot, the problem gets worse as the pin oxidises, and the higher resistance causes more heating, and the end result is the state of Pin1 in your plug. Maybe someone then had the idea to move the wire to Pin4 instead. That would work just as well as Pin1. It looks to me like the Pin1 pin in the socket is also burned to some extent.

Yellow is the colour that Hymer uses for the D+ signal, so I don't know what's going on there. You could test that wire to see if it's the D+ or the output from the other fridge relay. To tell the difference, there is a 20A fuse near the starter battery that supplies the fridge relays. Removing that should cut any power from Pin1 and Pin4. If there is a voltage on that yellow wire when the engine is running, then it's the D+ signal, not a fridge relay output.

The other yellow wire could be to switch on something like a B2B charger that might have been added as an upgrade, for charging the leisure battery from the alternator/starter battery instead of using the split charge relay (= Battery cutoff relay in the diagram).

Can you get at the wiring at the back of the fridge? Usually you can remove the lower external fridge vent quite easily, for access to the wiring. Maybe the yellow wire goes to there.

 

[Lizbiebrowne]

I can't see what model number of EBL it is, but I'm guessing it's an EBL99. The fridge supply comes from either Pin1 or Pin4. The difference is that Pin4 also gets power from the leisure battery when the engine isn't running, but Pin1 just goes off. That power comes through the fuse labelled 'Kompr/AES Kuhlschrank) (Kuhlschrank - fridge), so if that fuse is removed Pin1 and Pin4 are identical.

The pins are running at their full design capacity of about 15A for a fridge element, so it doesn't take much of an imperfection to start the pin heating. As it gets hot, the problem gets worse as the pin oxidises, and the higher resistance causes more heating, and the end result is the state of Pin1 in your plug. Maybe someone then had the idea to move the wire to Pin4 instead. That would work just as well as Pin1. It looks to me like the Pin1 pin in the socket is also burned to some extent.

Yellow is the colour that Hymer uses for the D+ signal, so I don't know what's going on there. You could test that wire to see if it's the D+ or the output from the other fridge relay. To tell the difference, there is a 20A fuse near the starter battery that supplies the fridge relays. Removing that should cut any power from Pin1 and Pin4. If there is a voltage on that yellow wire when the engine is running, then it's the D+ signal, not a fridge relay output.

The other yellow wire could be to switch on something like a B2B charger that might have been added as an upgrade, for charging the leisure battery from the alternator/starter battery instead of using the split charge relay (= Battery cutoff relay in the diagram).

Can you get at the wiring at the back of the fridge? Usually you can remove the lower external fridge vent quite easily, for access to the wiring. Maybe the yellow wire goes to there.

Thanks for your help - it's an EBL 100. I've had a look at the back of the fridge this afternoon:

The blue/brown/yellow wires entering from the top mimic the colour of the wires at Block 1 on the EBL. There's leisure battery voltage across the brown and blue wires that drops to 0 V if I remove the Plug at Block 1 or remove the 20 A fuse on the EBL. I didn't measure across the yellow and the brown - I'll do that tomorrow. The cable underneath with the black/white/red wires leads to the fridge. Someone has tapped into the connectors to draw a 12 V supply for a TV (the red and black wires), probably not a good idea.

The ends of the cables are corroded so I plan to tidy them up with Wago connectors once I can source some that accept 6 mm2 cable.

Interestingly there is a floating red cable at the other side of the recess terminating in a female spade connecting. Perhaps this has been used as a substitute D+ signal in the past?

Thank you for you help, very much appreciated. The EBL is a new mystery to me but that's the fun, working out and understanding.
Cheers.

 

[Lenny HB]

I can't see what model number of EBL it is, but I'm guessing it's an EBL99.

Read the thread title dear boy.

 

[autorouter]

The blue/brown/yellow wires entering from the top mimic the colour of the wires at Block 1 on the EBL. There's leisure battery voltage across the brown and blue wires that drops to 0 V if I remove the Plug at Block 1 or remove the 20 A fuse on the EBL. I didn't measure across the yellow and the brown - I'll do that tomorrow. The cable underneath with the black/white/red wires leads to the fridge. Someone has tapped into the connectors to draw a 12 V supply for a TV (the red and black wires), probably not a good idea.

There are two separate 12V supplies to the fridge. The Low Current (LC) supply powers the fridge control board, gas solenoids, igniter etc, and comes from the leisure battery. It is on all the time. The High Current (HC) supply powers the fridge 12V heating element only, and comes from the alternator/starter battery via a 20A fuse near the starter battery. It is switched by a relay inside the EBL, and that's the wire coming out on Pin4 of Block 1. It's usually arranged so that it's only on while the engine is running.

The fridge control board needs a D+ signal so that it knows when the engine is running, and can switch over to 12V. That's the yellow wire. Any signal that is about +12V when the engine is running, and about zero when the engine is stopped, will be OK for this. So instead of the genuine D+ signal, a signal from the fridge relay would work just as well. I think that was the idea behind connecting the yellow wire to Pin1 Block 1. Anyway, you can see there's not going to be anything going via Pin1, so something needs fixing there. Maybe there's a problem with the genuine D+ at Block1 Pin2. If not, you could try putting the yellow wire back on Pin2.

Those connectors are MnL (Mate'N'Lok) types. Shells and pins are available as kits or separately from automotive electrical suppliers, like 12VoltPlanet. Crimp the pin onto the wire using NON-insulated crimp pliers, and slide the pin into the shell until the barbs click and lock it into place.

Mate N Lok Universal Connector Pair - 4 Way

4 way Mate N Lok connectors for 0.5-2.0mm² cable provide secure and robust multiple connections. Supplied as a pair of male/female housings with all terminals.

www.12voltplanet.co.uk

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[Lizbiebrowne]

Thank again for the detailed information, it is much appreciated . It's too wet outside today to work through your replies, hopefully the weather will be better tomorrow. And thanks for the link, I've ordered a couple of the 4-way connectors from 12V Planet today.

 

[autorouter]

If the fridge has a manual selector, then it can work from 12V without the engine running. If the Kompr/AES Kuhlschrank fuse is inserted, then the 12V power for the element will come via that fuse from the leisure battery, to Block 1 Pin4, and out to the fridge. This works when the engine is not running, taking power from the leisure battery via that fuse.

This is not used very much for 3-way fridges, because the 12V element takes so much power, it can drain a battery in a few hours. I only use it when on a ferry or the Tunnel, when you have to turn the gas off. It's so easy to forget, and drain the battery. But you could use it for testing purposes while you are trying to get the fridge working.

When the engine starts, the relay flips and gets power from the alternator/starter battery.

 

[Lizbiebrowne]

The N145 fridge does allows for manual selection of the energy source although when I manually select 12 V I get a red flashing LED error after a few seconds. I've measured 12 V across the Blue and Brown wires at the connection to the fridge (falling to 0 V when the Kompr/AES Kuhlschrank fuse is absent) but I'm making an assumption that these are the cables coming out of Pins 4 and 3 respectively at Block 1. Does the 12 V come via the Blue wire whichever battery is powering the fridge or is it via the Blue when from the starter battery and via the Yellow when from the leisure battery (with Brown the common -ve)?

Thinking about your comment about draining the leisure got me thinking that using a 12V signal that not a D+ signal will lead to a flat starter battery rather then a flat leisure battery when the engine isn't running. And this chimes with something a previous (but not the last) owner told me when I spoke with him - he'd had a switch fitted near the fridge that he told me he had to switch off to stop the battery going flat. I can see the back of this switch from the inside of the bottom fridge vent - there's no connections to it now but it's close to where the redundant floating red wire I found that is carrying 12 V. So I'm wondering has there been a historical problem with the D+ signal necesssitating the use of a surrogate 12 V signal but a switch was needed to turn this signal off when the van was stopped and not on EHU to prevent flattening a battery?

 

[autorouter]

You are correct in that the wires from Block1 Pins 4 and 3 take power from either battery. The fridge relay is a changeover type, so it sends power from the leisure battery when not energised (ie no D+) and switches to starter battery when energised by the D+.

At the fridge end, the fridge control board set to auto won't switch on the 12V element unless the D+ (or a simulated D+) is present. So on Auto the fridge should only be on when the engine is running, and go off automatically when the engine stops.

If 12V is selected manually, the 12V element should switch on, with power coming from the leisure battery via the Kompr/AES Kuhlschrank fuse.

Can you see if there is a D+ signal coming out of the socket of Block1 Pin2? I imagine for some reason it's not there, otherwise the yellow wire would be connected to it. But if it is, it could be used. And is there any indication where that other yellow wire goes?

While you are tidying up the fridge connections, you could test the fridge 12V element., which will be the red and black wires I think. The resistance should be about 0.7 ohms, because the element is probably about 200W. That's a bit close to the lowest resistance a standard multimeter can measure, but you should be able to tell if it's shorted, open or working OK.

Also, does the fridge still work on 240v/gas when the Kompr/AES Kuhlschrank fuse is removed? I know it should still work, but I can't see the LC supply to the control board, so wondering if it's powered by that route instead.

 

[Lizbiebrowne]

You are correct in that the wires from Block1 Pins 4 and 3 take power from either battery. The fridge relay is a changeover type, so it sends power from the leisure battery when not energised (ie no D+) and switches to starter battery when energised by the D+.

At the fridge end, the fridge control board set to auto won't switch on the 12V element unless the D+ (or a simulated D+) is present. So on Auto the fridge should only be on when the engine is running, and go off automatically when the engine stops.

If 12V is selected manually, the 12V element should switch on, with power coming from the leisure battery via the Kompr/AES Kuhlschrank fuse.

Can you see if there is a D+ signal coming out of the socket of Block1 Pin2? I imagine for some reason it's not there, otherwise the yellow wire would be connected to it. But if it is, it could be used. And is there any indication where that other yellow wire goes?

While you are tidying up the fridge connections, you could test the fridge 12V element., which will be the red and black wires I think. The resistance should be about 0.7 ohms, because the element is probably about 200W. That's a bit close to the lowest resistance a standard multimeter can measure, but you should be able to tell if it's shorted, open or working OK.

Also, does the fridge still work on 240v/gas when the Kompr/AES Kuhlschrank fuse is removed? I know it should still work, but I can't see the LC supply to the control board, so wondering if it's powered by that route instead.

Weather's better today. I measured the voltages today at the Block 1 pins using Pin 3 as the ground with the engine on and off:

The Yellow cable from Pin 1 connects the White wire of the cable coming out of the fridge (see photo in Post 3). The resistance across all three combinations of the Black/Red/White wires is >200 ohms. With the cable from the EBL disconnected from the fridge cable (Post 3), the fridge will not switch on even when the mains is connected so I assume this cable is (also) providing the LC supply. There is another cable that goes to the fridge visible in the photo - I assume that is the 240 V supply?

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[autorouter]

That confirms what I think. 14.4V is the alternator/starter battery when the engine is running. 13.9V is the D+ signal from the alternator. 13.6V is the leisure battery when the engine is stopped.

I'll tell you what I think happened, but of course I might be wrong. At some stage in the past, a manual selection fridge was installed, which didn't need an LC supply. That had a problem, and burnt out Pin1 of Block 1. That was removed, and this fridge was bought to replace it. It was installed by someone who didn't know/care what they were doing, so that the HC supply powers both the LC and HC supplies on the fridge control board, and the D+ supply was bodged as well.

Usually on a fridge, the 5 wires (HC, LC and D+) are accessible at the back, and lead up to the control board which is probably located just behind the controls on the front of the fridge. Maybe you could access it, there's often an easy way to unclip it, but I don't know exactly how.

If you can access the control board, then you can identify and organise the existing wires and run other wires if necessary, so that the 5 wires come down to a 5-way terminal block where that 4-way terminal block is now.

Then run a pair of wires for the LC supply. One possibility is to take a supply from a 'spare' circuit on the EBL. For example, Block5 Pin6(+) and Pin11(-) would work, protected by the 'Reserve2' fuse. Check with a meter to confirm. You can use a couple of spare MnL pins to add the wires.

Then take a D+ supply from Block1 Pin2. Maybe use the existing yellow wire.

 

[Lizbiebrowne]

That confirms what I think. 14.4V is the alternator/starter battery when the engine is running. 13.9V is the D+ signal from the alternator. 13.6V is the leisure battery when the engine is stopped.

I'll tell you what I think happened, but of course I might be wrong. At some stage in the past, a manual selection fridge was installed, which didn't need an LC supply. That had a problem, and burnt out Pin1 of Block 1. That was removed, and this fridge was bought to replace it. It was installed by someone who didn't know/care what they were doing, so that the HC supply powers both the LC and HC supplies on the fridge control board, and the D+ supply was bodged as well.

Usually on a fridge, the 5 wires (HC, LC and D+) are accessible at the back, and lead up to the control board which is probably located just behind the controls on the front of the fridge. Maybe you could access it, there's often an easy way to unclip it, but I don't know exactly how.

If you can access the control board, then you can identify and organise the existing wires and run other wires if necessary, so that the 5 wires come down to a 5-way terminal block where that 4-way terminal block is now.

Then run a pair of wires for the LC supply. One possibility is to take a supply from a 'spare' circuit on the EBL. For example, Block5 Pin6(+) and Pin11(-) would work, protected by the 'Reserve2' fuse. Check with a meter to confirm. You can use a couple of spare MnL pins to add the wires.

Then take a D+ supply from Block1 Pin2. Maybe use the existing yellow wire.
View attachment 795514

Thanks Autorouter, that sounds like a good working hypothesis. I had a look at the wires at the back of the fridge today, they disappear behind a plastic cover that bears the label "Gas solinoid". It's held on by three or four screws that I think I can get to and remove but I'm not sure I can completely remove the cover as the incoming gas pipe runs close to it. I could undo the union where the gas connects to the fridge but I'm wary of doing that. I'll see how far I can get. Would the original LC supply also have come from the EBL and, if so, whereabouts? Many thanks.

 

[autorouter]

If the original fridge had manual switching not AES, then there may not have been any LC wires originally. So if the new fridge needs an LC supply, it's a matter of running a pair of new wires from the EBL to the fridge.

On my fridge (2006) the LC supply comes from one of the general circuit fuses, labelled Kreis1 and Kreis2. There's a pair of wires from the EBL to a multiway spade terminal block located near the Truma heater, which is quite near the fridge. The various wires, including the fridge LC supply, come from there. If there isn't a similar arrangement for your MH, then you could run wires from a spare (Reserve) connection, like the two terminals on Block 5 I suggested earlier.

I don't know how you access the control board to connect wires to it, but there must be a good way to do it, it would be needed for any installation. Maybe others have installed a fridge of this type. On Dometic fridges, the wires are all taken down to a terminal block at the back of the fridge at the bottom.