# Adria Coral fridge not working on 12 volt



## Nick Heaton (Mar 14, 2020)

I have recently purchased a 2007 Adria Coral 650 SP on the Fiat Ducato x250 chassis. It has the Dometic RM7655 AES fridge fitted, connected to an Electroblok EBL225. The fridge works fine on 240v and gas. However when you start the engine with the fridge set to auto, it does not switch to 12v operation. If you select 12v manually the indicator light glows red which according to the manual means a fault. I assume that there is a fault with a relay somewhere that is preventing the changeover between functions. Has anyone any ideas or suggestions please, before I take it to a professional?


----------



## jiwawa (Jun 22, 2007)

I can't answer that Nick but I would say no need to worry about it in the short-term. The fridge will hold its temperature pretty well for the duration of your journey.


----------



## Penquin (Oct 15, 2007)

Our Swift has two relays and appropriate fuses located above the engine behind the air filter under the scuttle in a black box. One of these relays controls the power supply to the fridge which only functions when the engine is running, the other controls the retractable step.

The failure of these fuses was the original reason I joined MHF many years ago - our step did not retract when the engine started, when advised by a very helpful MHF member - problem solved in a few hours....

It might be worth checking if you have a similar fuse and relay box and checking the fuses there - you may be able to locate a fault....

BUT if an indicator light us glowing red, that would make me believe there IS a 12v supply to the fridge when the engine is running, so, unless your 12v supply to the back of the MHstays on when the engine is running (ours does not as it is British built) it may be that it is indicating a fault in the heating element for the fridge - at which point only a fridge engineer can sort that out - Mr Google should be able to help you identify a suitable engineer near you.

Since your MH was built in Slovenia, the wiring is not required to conform to the National Caravan Council's requirements for registration as a motorhome in the U.K. So I suspect the red light indicates a fault as I said, in the heating element.
.


----------



## Nick Heaton (Mar 14, 2020)

Hi Penguin. Thanks for replying. Is you Swift on the x250 chassis? If so can you help me identify the fuse and relay box you refer to? Ours is located on the right hand side of the engine bay as you view the vehicle from the front. Also do you reckon there are two heating elements on the fridge ie one for the 12v and one for the 240v, or does 240v get get transformed to 12v to run the system

PS the Adia S 650 SP which is the model we have is an NCC inspected and approved motorhome


----------



## rayc (Jun 3, 2008)

Nick Heaton said:


> Hi Penguin. Thanks for replying. Is you Swift on the x250 chassis? If so can you help me identify the fuse and relay box you refer to? Ours is located on the right hand side of the engine bay as you view the vehicle from the front. Also do you reckon there are two heating elements on the fridge ie one for the 12v and one for the 240v, or does 240v get get transformed to 12v to run the system
> 
> PS the Adia S 650 SP which is the model we have is an NCC inspected and approved motorhome


Nick, My 2013 Coral had an input from the cab battery that went to the EBL via a 20A fuse close to the it. An output from the EBL, protected by a fuse marked 'fridge', fed to the fridge where there was a relay fixed to the rear. This relay operates from a negative signal that the alternator outputs when it is running, this is normally called the D+ signal. Therefore the fridge 12v element gets voltage ONLY when the engine is running.
The 240v element is completely separate and the fridge control simply switches the mains throught to it when EHU is present and mains is selected.

Can you confirm the make and model of the fridge and take photos of the area around the EBL and the rear of the fridge.


----------



## Penquin (Oct 15, 2007)

Nick Heaton said:


> Hi Penguin. Thanks for replying. Is you Swift on the x250 chassis? If so can you help me identify the fuse and relay box you refer to? Ours is located on the right hand side of the engine bay as you view the vehicle from the front. Also do you reckon there are two heating elements on the fridge ie one for the 12v and one for the 240v, or does 240v get get transformed to 12v to run the system
> 
> PS the Adia S 650 SP which is the model we have is an NCC inspected and approved motorhome


The fuse is as I said, up behind the air filter underneath more or less where the windscreen would be if it went down through the metal that supports it. You need to remove the air filter (easy job) then look and feel behind for a totally separate fuse box, black in colour and about the size of four cigarette boxes on top of each other (not much use in today's non-smoking world) -about 10 x 8 x 8 cm. it is NOT in the same box as you are describing but totally separate and unlabelled in any diagram ((typical Swift).

Open the bonnet, find the air filter and then look and feel all around that area, going as far back towards the driving/passenger seats as you can... it took me only a few minutes of looking, with a torch and long fingers.... Once found it is VERY obvious and ONLY contains two relays and a fuse holder with two fuses, nothing else at all. The black cover comes off easily without tools.

Have a look, just in case my vehicle is not unique - others have found the same box in similar, if not identical places.

BUT, Istill think that if the red light comes on when the engine is running on the fridge then power is getting there, but summat ain't right with the 12v heater (not thermostatically controlled I believe).


----------



## rayc (Jun 3, 2008)

I have attached the electrical schematic of the RM76x5 L fridge. I hope this helps. This system replaces the old fashioned split charging systems used in previous generations with relays attached to batteries etc.

Basically at top left of the drawing is the permanent dc supply which operates the control circuits plus there is the D+ signal which goes negative when the engine is running. I believe the D+ signal is derived in the EBL where there is a switch that enables the D+ signal to be negative or positive. This system requires the D+ signal to be Negative.
RH side is " terminal block heating element DC". This gets a permanent battery negative on A which is connected to the dc element and a switched vehicle battery positive on B. There is a relay which connects the positive to the element when it operates. The relay operates when the D+ signal is present. Relay coil terminal 86 is permanently negative and relay coil 85 is positive switch from the Power Module when it senses D+ signal.

https://manualsbrain.com/en/manuals/1295931/?page=28


----------



## nicaf (Mar 25, 2012)

Hi rayc. I have attached a photo of the fridge. Can you confirm if there is a simple test i can perform to bypass the D+ alternator connection to verify the 12v heater is indeed working, presumably indicated by a green light on the fridge control panel?


----------



## rayc (Jun 3, 2008)

nicaf said:


> Hi rayc. I have attached a photo of the fridge. Can you confirm if there is a simple test i can perform to bypass the D+ alternator connection to verify the 12v heater is indeed working, presumably indicated by a green light on the fridge control panel?


There are a number of things I would do.
The first is to ascertain the voltage being received at the tag block in the centre of your photo when the engine is running. You can see that the bottom tag runs to the element and the top tag down to the relay. This relay switches the positive to the element when the control unit senses the D+. 
The D+ signal is the lower tag of the other block. The second thing I would do is check with a meter that this goes negative when the engine is running. The third is I would check the resistance of the element but only if the results from 1 & 2 confirmed voltages and D+ switching were ok. If you connect a negative to D+ contact then this replicates what the alternator is doing.


----------



## rayc (Jun 3, 2008)

rayc said:


> There are a number of things I would do.
> The first is to ascertain the voltage being received at the tag block in the centre of your photo when the engine is running. You can see that the bottom tag runs to the element and the top tag down to the relay. This relay switches the positive to the element when the control unit senses the D+.
> The D+ signal is the lower tag of the other block. The second thing I would do is check with a meter that this goes negative when the engine is running. The third is I would check the resistance of the element but only if the results from 1 & 2 confirmed voltages and D+ switching were ok. If you connect a negative to D+ contact then this replicates what the alternator is doing.


Be careful as I have looked again at the photo and it looks like the D+ signal could be looped to the incoming positive. That means the incoming element voltage is switched prior to the fridge presumably at the EBL. In any event what is the voltage at the terminal block?


----------



## nicaf (Mar 25, 2012)

Hi rayc. I have ascertained the fridge 12v system is working. I inserted a 15A fuse into the AES "Fuse only with AES Fridge" in the EBL. The fridge control panel displays a green light which would seem to indicate that the fridge is working fine. It therefore points to a faulty relay or fuse! I cannot get access under the EBL to see all the wiring setup without completely removing the EBL and solar panel controller.

I will carry out the voltage test as you suggest above.

Could the failure of the side markers and D+ fridge operation be connected?


----------



## rayc (Jun 3, 2008)

nicaf said:


> Hi rayc.
> Could the failure of the side markers and D+ fridge operation be connected?


I don't think so


----------

