Stewart Hendry Posted October 29, 2017 Share Posted October 29, 2017 Our Thetford N90 fridge isn’t working on 12v when travelling. The 20 amp fridge fuse on the Elektroblock EBL 99 is ok but using a voltage tester shows that there is no power in that circuit (sorry if I’ve not described it in pure terms but my electrical practical knowledge is pretty poor) The 12v lighting circuit is fine, as are all of the other outputs. Can anyone recommend a suitable person or company in the Manchester area who is a wiz with van electronics. Many thanks. Link to comment Share on other sites More sharing options...
Alanb Posted October 29, 2017 Share Posted October 29, 2017 Hi Stewie, What you really require is advice from Allan of aandacaravanservices, bou he is not logged on at the present moment. I have looked at an Electrobloc 99 diagram and have a few points for you to check. The refridgerator fuse on the Electrobloc is for a compressor fridge. From reading the diagram I would expect to find an inline 20A fuse connected to the starter battery +ve terminal. The 12V power for the fridge only passes through the Electrobloc to allow control by the fridge relay, it does not come from the same source as the lighting etc. For the fridge to function on12V you will also need a nominal 12V D+ signal to operate the fridge relay in the Electrobloc. The D+ signal rises to 12V when the vehicle alternator is generating. This D+signal is also used to operate the split charge relay. You can therefore confirm that D+ is OK to the Electrobloc, by checking that the habitation battery takes a charging current with the engine running. If your D+ signal does not rise to 12V when the engine is started, the charge/battery warning light on the vehicle fascia will stay illuminated. Then you have a serious vehicle problem. Hope that the above helps and is not too technical. Alan Link to comment Share on other sites More sharing options...
Robinhood Posted October 30, 2017 Share Posted October 30, 2017 Stewart, reinforcing Alan's post. Converters using Schaudt electronics use all kinds of confusing wiring practice for refrigerators, particularly for AES (or Thetford equivalent) variants (I believe yours is manual). The most likely location for the fridge fuse for a manual, absorption fridge such as yours is not in the EBL itself, but inline in the wiring from the vehicle (starter) battery. (and is most often located adjacent to the positive terminal of the same). Conventionally a 20A fuse, it has been known to be higher rated. If you find a group of fuses in that location, then it is worthwhile checking them all, particularly if there is also a 2A fuse, as this is likely to be protecting the D+ signal (which is also required for the fridge to work on 12V). Incidentally, I've just been diagnosing rather odd AES fridge operation on a friends Dethleffs. That is wired in the (very) unconventional manner that allows running off 12V without the engine running! (and which has been outlined on here in the past). I'm pretty sure I've got to the bottom of his (suspected 240v) problem, but need him to pluck up courage to resolve it cheaply, rather than replacing the AES PCB, at a cost of around £200. If/when he does so, I'll post details on here. Edited to correct which battery (I had a senior moment). Link to comment Share on other sites More sharing options...
StuartO Posted October 30, 2017 Share Posted October 30, 2017 My Hymer allows running the fridge on 12v when the engine isn't running and the 12v power supply for the fridge comes from the EBL, which in my case is a 101. My fridge is a Dometic too, so not the same as yours. It should be possible to check that 12v is reaching the fridge by looking for the 12v connections via the outside ventilation panels and using a simple voltage tester or multimeter. Alternatively your fridge might (as mine does) have a panel light which comes on when 12v is selected. If there is 12v to the fridge but the fridge won't get cold when 12v is selected, the likely fault is the 12v heating element, which is replaceable. If you can access the 12v connections behind the fridge you should be able to do a continuity test of the 12v element. But you probably wouldn't want to tackle replacing that yourself because it usually means disconnectin the gas supply and taking the fridge out. Link to comment Share on other sites More sharing options...
Alanb Posted October 30, 2017 Share Posted October 30, 2017 StuartO - 2017-10-30 10:37 AM My Hymer allows running the fridge on 12v when the engine isn't running and the 12v power supply for the fridge comes from the EBL, which in my case is a 101. My fridge is a Dometic too, so not the same as yours. There is a difference here. The EBL 99 has two fridge relays one of which is dedicated to an "Absorber refridgerator" (not AES), with separate 12V outlet connection. The EBL 101 has only one fridge relay and both Compressor/AES and Absorber connections are connected to the same point inside the Electrobloc. Alan Link to comment Share on other sites More sharing options...
Robinhood Posted October 30, 2017 Share Posted October 30, 2017 Alanb - 2017-10-30 11:14 AM There is a difference here. The EBL 99 has two fridge relays one of which is dedicated to an "Absorber refridgerator" (not AES), with separate 12V outlet connection. The EBL 101 has only one fridge relay and both Compressor/AES and Absorber connections are connected to the same point inside the Electrobloc. Alan ....though, even in this arrangement, if wired as designed (and they aren't always so ;-) ) 12V operation with the engine running is still dependent on an external (nominally 20A) fuse in circuit with the vehicle battery, with the 20A fuse installed to the EBL being designed to protect an AES/Compressor fridge circuit from the leisure battery only when the engine is NOT running (switching between the two circuits being by means of a relay internal to the EBL, and the 20A EBL fuse shouldn't be installed on the EBL101 for a manual absorption fridge). The relevant fuses to be checked by the OP are those that should be adjacent to the Vehicle battery. Link to comment Share on other sites More sharing options...
747 Posted October 30, 2017 Share Posted October 30, 2017 That is correct, look under the bonnet, close to the battery for the 2A and large fuse (40 or 50 A). If they are OK then it could be the fridge relay at fault. Link to comment Share on other sites More sharing options...
Stewart Hendry Posted October 30, 2017 Author Share Posted October 30, 2017 Many thanks for your replies which have been most helpful. What is known is that the fridge is showing fault code 10 of which much has been written in this forum and that no power is showing at the connections accessed through the external vent cover. A friend has recommended someone who has worked on his van and having spoken with the contact he has a fair experience of the Elektroblock and AandN caravan services who are specialists in this area so I am confident a solution will be found. Link to comment Share on other sites More sharing options...
aandncaravan Posted October 31, 2017 Share Posted October 31, 2017 Hello, sorry been on holiday to Llanberis for a few days for the Snowdon Marathon, not to take part but support friends. Stewie, As all the others have said the key are the three fuses next to the Starter battery, a 50a, 2a and a 20a, or a variation on that depending how many times they have been swapped already. These are not with any vehicle fuses, but typical 'add on' fuseholders. The yellow 20a fuse is usually the cause of issues like yours. They often run near the limit, melt or corrode. If you have a Fridge/Freezer, then think about swapping the fuse for a quality 25amp version (and maybe a switch to a Maxi Fuse holder) as we have seen these drawing over 17amps. . Again as described above the fuse on the front, second from left, of the EBL, that should say "only populate fuse slot for emergency AES Fridge use" is often not even wired up by the Motorhome Builder. The Schaudt wiring diagrams are 'suggestions' for installation. Burstner tend to follow the Schaudt guidance but many others won't have a 12v wire coming out of Block 1 Pin 4 to enable the fuse in the front of the EBL, second from left. We had one Dethleffs, from the factory, wired using the 20 amp AES fuse point to provide the permanent 2a power for the Fridge controller PCB, rather than the 12v heating Element. Unless the fuse slot was populated, the Fridge/Freezer did not have the power to run even on Gas or 230v. With some Adrias, the Fridge permanent 12v PCB feed is taken from the nearest lighting circuit, even though the EBL 226 has a dedicated 2a fuse slot for the purpose of "Fridge Control". Never seen it 'wired correctly' yet. So Robin Hood be wary about what you expect to find and what is actually there on your friends Motorhome. Alanb, the EBL 101 is wired differently with a single relay but if the 20a AES fuseholder is populated it will supply limited Leisure battery power to both Block 1 Pin 1 and 4, but when the Relay switches because the Alternator has started spinning, the relay will 'take over' the power supply. It might be a parallel supply, but the real power will come from the Alternator. Some later Fridges also have direct D+ activation, taken from EBL 101 Block 1 pin 2 D+ Output, just for control of the Fridges own 'auto switching' as well as the external 12v element switching via D+. Link to comment Share on other sites More sharing options...
Stewart Hendry Posted October 31, 2017 Author Share Posted October 31, 2017 Thanks Allan, I’ll check all fuses you mention. As I said in my original posting I’m fairly useless when it comes to electrical matters so other than basic things my view is it’s best left to the experts. Link to comment Share on other sites More sharing options...
Robinhood Posted October 31, 2017 Share Posted October 31, 2017 aandncaravan - 2017-10-31 9:12 PM So Robin Hood be wary about what you expect to find and what is actually there on your friends Motorhome. ...oh, I know what's there, I've been over it with a fine toothcomb! It is a Dethleffs with AES fridge, and isn't wired as I would want mine to be. His problem, however, was an odd one. His fridge was overcooling in on-site use. In addition, he discovered when he got home that, even with everything ostensibly turned off, his fridge would still run (and overcool) if he hooked up! Cutting a long story short, the 12V circuit was eliminated (he was under the impression that he was also losing battery capacity - but I found no evidence to support it.). The charger and fridge were on the same MCB, so no chance of isolating the feed to the fridge there (at least whilst still maintaining 230V input) so the 230V feed to the fridge was disconnected at the back. The fridge stopped cooling, confirming a 230V issue. The fridge was then run off the leisure battery in what you term "emergency" mode. (Simply manually selecting 12V on the fridge control panel allowed this, and the battery was simultaneously being charged, just about keeping pace). Everything worked fine, with no overcooling, confirming the thermostat was OK. After much thought, the only possible cause of the problem was a stuck 230V relay (which, unlike the 12V relay, which is on the back of the fridge, is actually on the AES PCB). The 230V supply enters the PCB, goes immediately through the relay, and exits again. The rest of the PCB (as far as 230V operation is concerned) is simply 12V circuitry for source selection and thermostat sensing, which then switches the 230V relay as and when 230V cooling is required/requested. A replacement PCB is extremely expensive, and since the relay appears to be fairly readily available (its a 12V switched/400V max switched voltage type costing under £5), and is fairly clearly "spaced" on the PCB, my recommendation is to extract the PCB (fiddly but entirely possible) remove and replace the relay (6-pins to unsolder/ resolder) and re-install and test. Of course, there may be other problems on the board (but it shares much of the function between 12V - which is working fine - and 230V, so even if he pays his local electronics friend to do the soldering, it's worth a punt). I'm waiting for his feedback (though I've told him, I'd do it for him if the board looks accessible). Link to comment Share on other sites More sharing options...
Stewart Hendry Posted November 3, 2017 Author Share Posted November 3, 2017 Problem solved- nothing more than a missing D+ feed but took some finding. Thanks again for all of your very helpfull comments, much appreciated. Stew Link to comment Share on other sites More sharing options...
Robinhood Posted April 17, 2018 Share Posted April 17, 2018 ..time for a quick update on my last post. To recap, the problems on my friend's fridge were diagnosed by me as being 95%+ probability a stuck 12v/240v relay on the AES PCB. The fridge has been disabled since October by 'unwiring' the 240v heater, and likewise my friend has been disabled by a bad hip :-(. Last week, he got back in touch and bit the bullet. PCB was removed, the relay was tested in situ and appeared faulty. Removing the Dometic paper sticker from the component revealed a Panasonic part number, not actually the one I expected from prior research, but still readily available and c£4 delivered via eBay. He'd already identified a local PCB repairer who would do a straight swap (no diagnostics) for a fiver, so away he went. I'm still awaiting final confirmation that everything is working, but it was replaced last night, and 240v operation so far has been exemplary. A replacement PCB is in the order of £200, and it appears that he might have got away with <£10. If everything checks out, I'm going to be quite chuffed (and so, no doubt, is he :-) ) Link to comment Share on other sites More sharing options...
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