MAB Posted August 3, 2015 Share Posted August 3, 2015 Hoping I can get some help with my Fridge problem installed in my Bessacarr E720. The 12V Control Board supply to my Dometic RM7401 fridge is faulty (0V) and I suspect the wiring/connections may have developed a high resistance/open circuit fault. I checked the supply feed at the terminal block fitted to the top of the fridge which is reading 0V. The Leisure battery itself is fine. I'm now trying to trace the Black sheathed cable with the Purple +ve & Black -ve wires terminated on the other side of the terminal block back to its origin. Anyone know where it goes on its way to the Leisure battery? The cable disappears between the fridge chassis and the cabinet carcass, but I'm unable to see where it goes without pulling the fridge out. I'm not sure if there is a separate in-line fuse for the fridge electronics supply. The hand book wiring diagram is little help as it doesn't appear to show the separate 12V electronics supply. Thanks Mark Link to comment Share on other sites More sharing options...
Keithl Posted August 4, 2015 Share Posted August 4, 2015 Mark, What year is your Bessie? Link to comment Share on other sites More sharing options...
sshortcircuit Posted August 4, 2015 Share Posted August 4, 2015 Are there any other appliances not operating and have you checked the fuses at the consumer unit? Link to comment Share on other sites More sharing options...
MAB Posted August 4, 2015 Author Share Posted August 4, 2015 2006 - Last of the 2nd Generation 2.8 JTD model Link to comment Share on other sites More sharing options...
MAB Posted August 4, 2015 Author Share Posted August 4, 2015 Everything else works fine. I can apply a separate 12 V feed to the control board and all works ok. Link to comment Share on other sites More sharing options...
MAB Posted August 4, 2015 Author Share Posted August 4, 2015 Is the 12V electronics power to the control board fed from the consumer unit? Link to comment Share on other sites More sharing options...
Guest Joe90 Posted August 4, 2015 Share Posted August 4, 2015 My understanding is the fridge 12 volt supply comes via a relay from the engine battery, but only when the vehicle has been started, that may explain why you are not getting a voltage reading. Link to comment Share on other sites More sharing options...
MAB Posted August 4, 2015 Author Share Posted August 4, 2015 There are 2 x 12 V supplies. The first is the electronics 12 V supply which I understand should be a continuous feed from the Leisure battery. Without this 12 V to the electronics the fridge is inoperable. The second 12 V which you refer to is the power feed for running the fridge from 12 V as an alternative to mains or gas power. Link to comment Share on other sites More sharing options...
Guest Joe90 Posted August 4, 2015 Share Posted August 4, 2015 It may not be the same as yours, but my fridges electronic permanent 12 volt supply IS taken from the engine battery, a separate relay being employed to switch to the high current drain 12 volt supply to operate the fridge once on the move. How do I know this, because I recently serviced my fridge, disconnected the leisure battery and it was all still live, including the power to the electronics control board, which I must admit surprised me, but might be worth investigating yours in case it is the same, ;-) Link to comment Share on other sites More sharing options...
sshortcircuit Posted August 4, 2015 Share Posted August 4, 2015 MAB - 2015-08-04 10:22 AM There are 2 x 12 V supplies. The first is the electronics 12 V supply which I understand should be a continuous feed from the Leisure battery. Without this 12 V to the electronics the fridge is inoperable. The second 12 V which you refer to is the power feed for running the fridge from 12 V as an alternative to mains or gas power. Correct, in your instance. Have you been able to locate the fuse at the fuse board? If fridge working with applied external supply, then problem is elsewhere. Joe, are you able to switch off fridge totally as I would be concerned about flattening the starter battery, admittedly over time? Link to comment Share on other sites More sharing options...
Guest Joe90 Posted August 4, 2015 Share Posted August 4, 2015 Yes I can it's a Dometic RM7655, an off switch at the top, but no worries about batteries, I'm posh, I've got a solar panel linked up to both engine and leisure ones. ;-) as long as the sun puts in an appearance from time to time. :-( Link to comment Share on other sites More sharing options...
MAB Posted August 4, 2015 Author Share Posted August 4, 2015 Hi sshortcircuit I've not be able to locate the fuse. The only fuse location I can find, which I have checked are as follows, 20 A fuse at Leisure battery DC Fuses at the EC200 PSU Fuses alongside split charge relays in engine bay Are there other locations I should be looking? I read in some Dometic installation blurb that the electronics feed should be wired directly back to the Leisure battery with a 2A fuse included. To check the board is operational I applied my external 12V feed directly to the control board via some small clip probes. I'm hoping to not have to pull the fridge out to check the cable run. I'm also hoping to get some more detailed wiring information from the folks at Swift who are currently checking their document archive. Appreciate your help and suggestions. Link to comment Share on other sites More sharing options...
sshortcircuit Posted August 4, 2015 Share Posted August 4, 2015 This may help. http://www.sargentltd.co.uk/Swift_Motorhome_schematics_2006.pdf As other appliances are working fuse at leisure battery ok. The fuse at the split charge relays only provides a high current supply to the fridge pcb which connects to relay feeding 12v heater element. I am not familiar with the fridge but there may be a small glass type fuse on the pcb You have confirmed the fuse on the EC200 is ok It will not make any difference wether the control supply to the fridge is taken direct from leisure battery or from EC200 although a bit tidier with all fuses together. I am still suspicious about the output from the EC200. Please feedback how you get on Link to comment Share on other sites More sharing options...
MAB Posted August 4, 2015 Author Share Posted August 4, 2015 Thanks for your help sshortcircuit, So you would expect the 12 V feed to come from the EC200? Which makes sense and good to get some confirmation. I will revisit the connections and fuses when I'm back home later. The fuse on the PCB is fine as I can apply the 12 V external to this and the board powers up via the fuse no problem. On a different tact I recently had the cam belt replaced, and of course the starter battery would have been removed. Any chance something in this area could have been disturbed? Thx Mark Link to comment Share on other sites More sharing options...
sshortcircuit Posted August 4, 2015 Share Posted August 4, 2015 MAB - 2015-08-04 12:56 PM On a different tact I recently had the cam belt replaced, and of course the starter battery would have been removed. Any chance something in this area could have been disturbed? Thx Mark No Link to comment Share on other sites More sharing options...
Keithl Posted August 4, 2015 Share Posted August 4, 2015 MAB - 2015-08-04 12:56 PM On a different tact I recently had the cam belt replaced, and of course the starter battery would have been removed. Any chance something in this area could have been disturbed? Thx Mark Yes, possible! They may have left a wire off the positive battery connection. Always possible, never say never! Keith. Link to comment Share on other sites More sharing options...
sshortcircuit Posted August 4, 2015 Share Posted August 4, 2015 Keithl - 2015-08-04 1:20 PM MAB - 2015-08-04 12:56 PM On a different tact I recently had the cam belt replaced, and of course the starter battery would have been removed. Any chance something in this area could have been disturbed? Thx Mark Yes, possible! They may have left a wire off the positive battery connection. Always possible, never say never! Keith. I find that an intriguing comment considering "Everything else works fine". Need to look closer at circuit diagram :-D Link to comment Share on other sites More sharing options...
Guest Joe90 Posted August 4, 2015 Share Posted August 4, 2015 The OP has muddied the waters with his cambelt change comment, he's established that the electronics are powered from the leisure battery, ( I think ) so why he would throw that into the mix is hard to say. (?) Link to comment Share on other sites More sharing options...
MAB Posted August 4, 2015 Author Share Posted August 4, 2015 I threw it in because its a change to the vehicle and around the same time the Fridge stopped working. Just wanted to make sure it is just a coincidence. The cable routes are not obvious to me and I wouldn't be surprised if for some strange reason when the cable harnesses are constructed it takes some consulted route via the engine bay. Based on the info from sshortcircuit I will focus on the feeds and fuses from the EC200 as being the most likely area at fault. My suspicion is that the cable has got a dodgy connection between the EC200 and the terminal block on top of the fridge. If I can identify the cable out of the EC200 I can do a continuity test and check for an OC/High Resistance. From the wiring diagram there is a White/Orange wire from the EC200 to the Fridge which I presume is the 12 V electronic feeds. Somewhere under the floor/behind a cabinet its connected to the Purple plus electronics feed to the terminal block. Thx - Mark Link to comment Share on other sites More sharing options...
Guest Joe90 Posted August 4, 2015 Share Posted August 4, 2015 Ah I see, no stone left uncovered, good strategy, and that's what threw me when I serviced my fridge, assuming the electronics would be supplied from the leisure battery as I described earlier, only to find they were not, just as well I put a test meter on them at the back of the fridge before disconnecting everything, anyway, good hunting. ;-) Link to comment Share on other sites More sharing options...
Brian Kirby Posted August 4, 2015 Share Posted August 4, 2015 MAB - 2015-08-04 10:05 AM Everything else works fine. I can apply a separate 12 V feed to the control board and all works ok. Have you also tried disconnecting the existing 12V + feed at the Dometic terminal, and substituting your direct leisure battery 12V feed, so that you can be sure you have 12V at the terminal, as opposed to at the board? I'm just wondering whether there may be a dud connection between terminal and board. Unlikely, I agree, but worth eliminating? Link to comment Share on other sites More sharing options...
MAB Posted August 4, 2015 Author Share Posted August 4, 2015 Thanks Brian. I'm not getting 12 V at the terminal block on top of the fridge. So the cable from the terminal block to the control board is not the problem at this stage. Acting on sshortcircuits advise to focus on the EC 200 I spoke with the Sargent techie this afternoon and he pointed me to Pin 3 (Yellow/Brown) on the 15 pin connector at the bottom of the EC 200 (second from left connector). This is the 12 V feed that also happens to supply the radio. He told me there is an automatic fuse on board the EC200 circuit board, which self heals. The radio is working fine. I've checked at pin 3 at the EC 200 and I have 12V. So it points to an OC connection to the fridge. Now knowing which wire supplies the 12 V I've started to trace it back to the fridge. I have continuity up to the point it disappears behind the fridge and where it must connect to the Purple wire that provides the connection to the terminal block. From the outside if I remove the lower vent grill I can see the Yellow/Brown wire which passes behind the bottom of the fridge and then up the side which I can't get access to without pulling the fridge out. So my next job is to pull the fridge out and find what I suspect (and hope) is a bad connection between the Yellow/Brown wire to Purple wire change over. Will report back once I have the fridge out. Thx - Mark Link to comment Share on other sites More sharing options...
sshortcircuit Posted August 4, 2015 Share Posted August 4, 2015 Can you check at the radio first in case open circuit there. Link to comment Share on other sites More sharing options...
MAB Posted August 4, 2015 Author Share Posted August 4, 2015 Radio is working and I have continuity from Pin 3 of the EC 2000 all the way to the base of the fridge. It's the last meter from the base of the fridge to the terminal strip on top of the fridge that is OC. Probably where the change over takes place from the Brown/Yellow wire to Purple wire, which I don't currently have access to. Link to comment Share on other sites More sharing options...
Brian Kirby Posted August 5, 2015 Share Posted August 5, 2015 You may find the connector is accessible via the upper grille. It should be accessible via one or other, so that the fridge can be removed if necessary. Alternatively, if now that close to the fridge, why not install an accessible closed, weather proof, connector box beside the lower grille, cut back the existing wiring to that point, and run new to the terminal block? Surely easier than pulling the fridge out. Bit untidy, I accept, but just abandon the redundant wiring. Link to comment Share on other sites More sharing options...
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