# 12v Fridge Relay ?



## vicdicdoc (May 14, 2005)

I had a new Dometic fridge fitted around 18months ago (sadly out of warranty) the last time I used it on starting the engine & selecting 12v on the fridge (it's a manual selection model) - I noticed that the battery meter showed a large discharge, (it operates perfectly on gas & mains hook up), I suspect that the relay that was fitted has gone u/s . . . Is there a particular relay I should buy or is it a generic type relay ?


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## trek (May 1, 2005)

have read this a few times to get it clear in my mind I think you are saying that the engine is not charging the leisure battery ?

as the fridge when manually switched to 12v is drawing current from a 12v source ( probably the leisure battery ?) so the fridge is working correctly

maybe a fuse gone ?

but should be straight forward to check both fuse & relay operation if you have a multimeter


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## Penquin (Oct 15, 2007)

I would start by checking the fuse by the relay as that may be the source of the problem..... In our case the relay and fuse are fitted above the engine, tucked behind the air filter and under the bulkhead - there are two relays and two fuses - in ours the second controls the automatic step retraction when the engine is started.

Might be well worth checking before replacing anything....

I have tried to link to my post and the answers on that but MHF now seems to be limiting to searching the last 500 posts and I have made more than 11,000 so that is not very helpful.......

Dave


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## cabby (May 14, 2005)

Just to cause confusion, I was under the impression that the 12v feed for the fridge when engine running came direct via a relay from the alternator, NOT from the leisure batteries.With engine off the relay switches supply off.
The 12v feed that comes from the leisure battery is for the igniter and for the gas sensor.In other words keeps the Gas working.

cabby


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## 747 (Oct 2, 2009)

Cabby is correct.

Find the relay and check it with a meter to ensure it is wired in correctly and the wiring is sound. There is a lot of info online about the wiring connections.


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## Stanner (Aug 17, 2006)

I have a fridge relay problem at the moment where it seems to be sticking on and so not cutting off when the engine is stopped. 

In my case it is the starter battery that is being flattened when this happens and that would indicate that the 12v supply to the fridge is indeed from the +ve supply on the alternator.

My problem is that the relay appears to operate correctly when power is applied across the windings, but something is happening that leaves the windings energised even when the alternator isn't running.


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## trek (May 1, 2005)

I too agree with Cabby but reading Vicdicdoc's original description I interpreted the symptoms as though his installation could be using the leisure battery ?


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## 747 (Oct 2, 2009)

trek said:


> I too agree with Cabby but reading Vicdicdoc's original description I interpreted the symptoms as though his installation could be using the leisure battery ?


That is quite possible ...... but we will never know because we have no idea what vehicle he has. :frown2:


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## eurajohn (May 9, 2005)

I think the vehicle is an Hymer.
Whichever battery is being utilised, the normal procedure is for the main control unit to supply the power for the fridge, which is normally inhibited until the system sees a positive charge from the alternator.
If not using the main control unit a split charge relay is normally utilised which effectively does the same as the Electrobloc or whatever but only supplies 12 volt to the fridge when the alternator is supplying a charge, normally controlled via the circuitry that controls the dash charge light.


.


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## vicdicdoc (May 14, 2005)

747 said:


> That is quite possible ...... but we will never know because we have no idea what vehicle he has. :frown2:


Van is a 1997 Fiat Ducato based Hymer E-510.
The 12v IS from the vehicle battery not the leisure batteries, the fridge seems to draw a lot more amperage than it usually does that's why I suspect it's the relay.


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## 747 (Oct 2, 2009)

http://motts.org/SPLIT CHARGING SYSTEM.htm


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## Pudsey_Bear (Sep 25, 2008)

747 said:


> http://motts.org/SPLIT CHARGING SYSTEM.htm


Another Clive fan > I set mine up to use a *smartcom relay*, which was connected to the VB, it sensed the input voltage increase when engine started, and I used the fridge out put on it to trigger a HD relay which powered the the fridge from the VB, not the LBs.

The Hymen will use a similar system possibly, if not it could be modified as above if the parts needed were not available, costs about £20 ish plus cables if needed.


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## eurajohn (May 9, 2005)

vicdicdoc said:


> Van is a 1997 Fiat Ducato based Hymer E-510.
> The 12v IS from the vehicle battery not the leisure batteries, the fridge seems to draw a lot more amperage than it usually does that's why I suspect it's the relay.


What concerns me ref that information, is that a relay is simply a means of switching a load, it does not, or cannot increase the load used by an appliance.

.


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## vicdicdoc (May 14, 2005)

Thanks for all your input but as the fridge was working ok on 12v prior to couple of weeks back I'm still inclined to think it's the relay that's u/s and wanted to know if i need a particular relay or generic one would do to replace the 'faulty' one ? - if so can anyone point me to the one I need ?


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## Pudsey_Bear (Sep 25, 2008)

vicdicdoc said:


> Thanks for all your input but as the fridge was working ok on 12v prior to couple of weeks back I'm still inclined to think it's the relay that's u/s and wanted to know if i need a particular relay or generic one would do to replace the 'faulty' one ? - if so can anyone point me to the one I need ?


If you suspect the relay it will either have a type number, a drawing of how it works or a particular layout of the terminals with numbers, take it to a auto sparky or Motor store and get a identical one  if not HD they're dead cheap and will let you know if this is the problem, but as john said the current change is a different matter.

Can you post a pic of the relay away for where it lives?


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## 747 (Oct 2, 2009)

vicdicdoc said:


> Thanks for all your input but as the fridge was working ok on 12v prior to couple of weeks back I'm still inclined to think it's the relay that's u/s and wanted to know if i need a particular relay or generic one would do to replace the 'faulty' one ? - if so can anyone point me to the one I need ?


I'm sorry to say this but you have had all the right advice but it is useless unless you actually do something about it yourself. At some point you are going to have to find the relay, note the model and buy one. If you are not good at this sort of DIY then just take it to a Dealership or Auto Electrician.


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## vicdicdoc (May 14, 2005)

747
Of course I'll do something - I'll buy a new one !
(I was enquiring if anyone knew if I needed a specific one . . . & yes I'll take the suspect one out & get a new one


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## rod_vw (May 10, 2005)

I don't understand why you suspect the relay. As stated above a relay cannot increase the current being drawn. That can only be caused by a fault in the circuit beyond the relay, either in the actual fridge (heater unit) or in the wiring between the relay and the fridge.
I would suggest disconnecting the 12v feed at the fridge and see if the excess current draw is removed. If it is then the fault is within the fridge, if it is still present then there is a fault in the circuit between the relay and the fridge.
If the latter is the case just to prove the point disconnect the output wire from the relay to confirm that the current draw is now removed. (There is probably a circuit diagram moulded on the relay case). If you have now proved that there is a fault in the wiring between the relay and the fridge you will have to ascertain that there is nothing else connected to this circuit and trace the excess current draw.
Where ever you prove the fault to be it is either down to you as a good DIY electrician to fix it or pay an auto-electrician to fix it for you.


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## cabby (May 14, 2005)

We seem to be making this harder than it is, to start with the fridge is working on the 12v, when engine running, this means that the RELAY is working, it is only a switch, it does not control the amount of current supplied.

What we should be asking is whether that high demand is constant to start with, do you use the gas or 230v to cool first before using the 12v with engine running.As you have a meter, can you tell us what the fridge is demanding when at normal operating temp.

Silly question, sorry, have you had the vehicle battery checked. Even more, have you checked the alternator output to make sure it is not running wild.

cabby

ps. meant to ask, where is the meter you mention connected.


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## 747 (Oct 2, 2009)

vicdicdoc said:


> 747
> Of course I'll do something - I'll buy a new one !
> (I was enquiring if anyone knew if I needed a specific one . . . & yes I'll take the suspect one out & get a new one


At no time have I advocated you buying or fitting a new split charge relay.

What I have done is linked to a website that gives you the connections of a split charge relay so that you can check it with a meter. Depending on what you find will dictate the next step in the process of fault finding.


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## vicdicdoc (May 14, 2005)

Depending on the weather I'll go down to the storage compound & check those points raised - I'll be on my trusty Honda Innova & don't like riding in the wet.


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## Pudsey_Bear (Sep 25, 2008)

COME ON!!! we're all waiting to hear what's happening > >


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## Penquin (Oct 15, 2007)

Kev_n_Liz said:


> COME ON!!! we're all waiting to hear what's happening > >


Ooo err maybe he didn't get back in one piece.....

I well remember being told by a Supervising Paramedic that to ambulance staff (which I was trying hard to be....) that a SERIOUS accident to a Paramedic was when the casualty arrived at hospital in more than one vehicle.....:grin2:

I'm sure he got there AND back and that the weather was not soooo bad that he needed his water wings too....

Dave :laugh:


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## vicdicdoc (May 14, 2005)

Rained . . . So I postponed going the 8 miles to the storage compound till the sun shines :wink2:


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## cabby (May 14, 2005)

Not this month then.:wink2::wink2::wink2:

cabby


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## vicdicdoc (May 14, 2005)

cabby said:


> Not this month then.:wink2::wink2::wink2:
> cabby


You could be right . . . Rain rain rain


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## vicdicdoc (May 14, 2005)

I FINALLY got to go down to the van today . . . after a play with my volt meter I discovered (as I suspected) it was the 12v fridge relay . . (Chinese cr*p), New one now fitted & working perfectly - (although I hesitate to gloat as I don't want to tempt 'sods law')


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