Dometic RM4605 AES fridge/freezer

The unit will not switch to 12V. It will work fine on gas and also 240v but won't go to 12V while travelling. I found the fuse had blown in the rear of the fridge 20amp and replaced the fuse but it still won't switch. The car is sending the 12v through when the engine is running. I have measured the DC voltage at the fridge and measures as 13.2v. Does anyone have any advice please. The unit is just under 12 months old but I'm about to go away so would rather not have to take it in for repair if there is a simple solution.
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Reply By: Nomadic Navara - Sunday, Oct 14, 2012 at 21:37

Sunday, Oct 14, 2012 at 21:37
Few questions. Has it ever worked on 12 V? The fridge requires a permanent 12 V supply to operate its logic circuit as well as the second heavy 12 V supply from the alternator. Are both these wired correctly?
PeterD
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AnswerID: 496690

Follow Up By: 427 - Sunday, Oct 14, 2012 at 21:59

Sunday, Oct 14, 2012 at 21:59
Hi Peter, Yes the fridge has worked for almost one year. A bit of history... During this period I changed from a Prado to a Jeep Grand Cherokee. The fridge worked with the Prado and the auto-elec wired the Jeep and I checked his wiring and he also used a dummy board with lights to check. I have also installed solar to the van. This weekend was the first use of the Jeep towing the van and we found that the 12v DC side of the fridge not working. I have done some checking and found the 12v permanent is ok, I checked that at the fridge rear. I then checked the 12v supply wiring used to operate the logic circuit and found it working ok when the engine was running. The only problem I came across was a 20 amp fuse blown. The fuse connects the +12v supply wire to the terminal block. I replaced the fuse and it still does not work. Interestingly, the manual says it should be a 30 amp fuse.
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Follow Up By: Charlie B2 - Monday, Oct 15, 2012 at 12:51

Monday, Oct 15, 2012 at 12:51
Hi 427,

If the manual tells me it needs a 30 amp fuse and you're only running a 20 amp, I guess that's where I'd start! :-)

Anything else would need to re-checked after that!

I'm not saying that's your problem, because these faults can be a pain to track down, but a good place to start.

What kind of fuse does it run? If it's a 30AG (glass tube with two metal end-caps), I'd chuck the entire arrangement and start over - I've NEVER found them to be reliable enough for my use.

Regards,


Charlie
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Follow Up By: member - mazcan - Monday, Oct 15, 2012 at 13:00

Monday, Oct 15, 2012 at 13:00
hi charlie
i'll second what you've said the 20 amp fuse is acting as a power restriction
it beats why someone would install a 20amp fuse when the manual states 30amp isn't that just inviting problems into an electrical circuit????
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FollowupID: 772421

Follow Up By: Charlie B2 - Monday, Oct 15, 2012 at 13:28

Monday, Oct 15, 2012 at 13:28
Hi mazcan,

I'm no sparky of any kind, but I'd reckon it might!

And if the unit is either borderline on its requirement or happens to draw 22 or 23 amps in operating, it MIGHT let it through without blowing, or it might not.

By the way, if I haven't said so above, I might even argue that some fuses might not be absolutely precise on their blow-point!

QED - problem!

Charlie
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Follow Up By: 427 - Monday, Oct 15, 2012 at 14:47

Monday, Oct 15, 2012 at 14:47
Hi Folks,
Many thanks for your advice on the fuse. A point to make is: The Van is almost one year old and the 20amp fuse came with the van. Funny that it worked for almost one year! I happened to noticed that the Dometic guide said to use a 30amp fuse. As I noted the fridge worked with the Prado up until recently. The replacement fuse I put in yesterday was 20 amp and it has not blown. I will replace it with the recomended 30 amp, but expect no solution to the real problem that the fridge will not move to use the 12v DC supply.

Peter
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FollowupID: 772427

Follow Up By: member - mazcan - Monday, Oct 15, 2012 at 16:53

Monday, Oct 15, 2012 at 16:53
hi 427
have you checked the voltage right at the element on the fridge side of the inline fuse also if you a need a new element or anything else this site may be of use
www.rvdealership.com cheers
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FollowupID: 772435

Reply By: Nomadic Navara - Monday, Oct 15, 2012 at 23:33

Monday, Oct 15, 2012 at 23:33
I am not sure exactly what fridge you have. You have not disclosed that info so it's a little hard to give a full diagnosis. You may have a RM 2355, 2455, 2555, 4605 or 4805 so I will answer on those grounds.

You should actually have three 12 V feeds to the fridge, a heavy duty one from your alternator that is not switched, one from your vans house battery and one from an ignition switched circuit in the tug.

The D+ terminal is the one going to the ignition switched circuit in your tug. Its purpose is to allow the fridges logic circuitry to switch its 12 V input off and save the tugs starting battery. In the smaller size fridges the house battery and tug battery blocks are separated a bit.

If you have a much earlier AES fridge then this may not apply. If you had have given full details I could possibly downloaded the correct instructions.

PeterD
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AnswerID: 496758

Follow Up By: 427 - Tuesday, Oct 16, 2012 at 08:53

Tuesday, Oct 16, 2012 at 08:53
The model is RM4605. I have checked the 12v DC to vehicle battery and the 12v DC to house (Caravan battery's). I have not checked as yet the D+ 12v at the fridge end. The car end and caravan connection are working fine. I have the wiring diagram and will check the D+ with vehicle running/not running.
Thanks,
Peter B
Retired ICT Project Manager
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Follow Up By: 427 - Tuesday, Oct 16, 2012 at 22:18

Tuesday, Oct 16, 2012 at 22:18
Update to the last post. No 12v at the D+ fridge end but 12v at the D+ car/caravan plug. Looks like the wire has either snapped or possible burnt out somewhere. My next concern is that I will run a new wire for the D+ for the AES logic circuit but have a problem that needs to be resolved first before turning back on. Why did the 20 amp fuse (I have replaced it with a 30amp as per Dometic manual) that Dometic supplied for the 12v DC vehicle burn out? I plan to run a new wire for the D+ under the caravan but add a fuse at the rear of the fridge for this new wire. Then turn off the solar (MPPT solar controller) at the switch to ensure this is not the problem and then test the fridge. If this works I will then turn the solar back on to ensure the solar controller and the AES controller are not in conflict which could have caused the problem. If all goes to plan I should be back in business.
Thanks,
Peter B
Retired ICT Project Manager
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Follow Up By: 427 - Wednesday, Oct 17, 2012 at 21:49

Wednesday, Oct 17, 2012 at 21:49
Update 17th October. The D+ 12v is dead at the fridge. I have run a new D+ 12v wire and all is working. Thanks to all for assistance.
Peter B
Retired ICT Project Manager
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