Still have not got 12v fridge feed working!

[Joggerdude]

I still have no 12v supply to 3 way fridge (Dometic RM7291L , Manually Selector for GAS/240v/12v).
I posted an earlier thread re this but got nowhere, so I will start again.

* Voltage to car fridge 12S is 13.8v (car running).
*Basic 5 pin relay where cables enter the caravan seemed to be working (was clicking) but I replaced anyway.
*When first switching fridge power source to 12v, Green 12v selected indicator light comes on but after 4 seconds starts flashing in time to the relay.
*As some suggested, I raised the revs on the car, but it made no difference, light still flashing (although light was previously always steady on, even at car idle speed).
*12v element seems ok as resistance is 1.4 ohms.

I am thinking that it is a fault in the main circuit board behind the fridges main top facia.
Gas and 240v work fine.

So, the big question is ...
Rather than pay out for a circuit board, would it be ok to run 12v direct from the relay at the front of the van directly to the 12v element (bypassing all the fridge wiring)?
I would also put a 12v switch and fuse in line.
This would only be active if the car was running as now.

Any thoughts
Thanks

 

[Jcloughie]

I still have no 12v supply to 3 way fridge (Dometic RM7291L , Manually Selector for GAS/240v/12v).
I posted an earlier thread re this but got nowhere, so I will start again.

* Voltage to car fridge 12S is 13.8v (car running).
*Basic 5 pin relay where cables enter the caravan seemed to be working (was clicking) but I replaced anyway.
*When first switching fridge power source to 12v, Green 12v selected indicator light comes on but after 4 seconds starts flashing in time to the relay.
*As some suggested, I raised the revs on the car, but it made no difference, light still flashing (although light was previously always steady on, even at car idle speed).
*12v element seems ok as resistance is 1.4 ohms.

I am thinking that it is a fault in the main circuit board behind the fridges main top facia.
Gas and 240v work fine.

So, the big question is ...
Rather than pay out for a circuit board, would it be ok to run 12v direct from the relay at the front of the van directly to the 12v element (bypassing all the fridge wiring)?
I would also put a 12v switch and fuse in line.
This would only be active if the car was running as now.

Any thoughts
Thanks

Your ideas seem logical and I think your plan might work. But two thoughts occur.

What is your use? Long distance and hot weather the fridge while traveling may be oh some use. Otherwise, a couple of hours in the country, makes very little difference. You can do better with ice packs or frozen milk.

Is the possible faulty circuit board affecting the normal running of the fridge? You may go to all this trouble only to find you need the board anyway.

John

 

[Joggerdude]

Your ideas seem logical and I think your plan might work. But two thoughts occur.

What is your use? Long distance and hot weather the fridge while traveling may be oh some use. Otherwise, a couple of hours in the country, makes very little difference. You can do better with ice packs or frozen milk.

Is the possible faulty circuit board affecting the normal running of the fridge? You may go to all this trouble only to find you need the board anyway.

John

Thanks John,
I have tested the fridge on mains voltage (what we always use on site), and it worked fine, 4 degrees when I checked.
We are due to do a 6 hour drive soon so it would definitely be worth it.
I'm just cautious to make sure I do nothing to damage the fridge and more importantly the car!
The front of van relay which I replaced (just in case) contains a diode, which presumably protects the car electrics?
I propose cutting the 12v element wires to separate it from any connection to the fridge, then splice it to the wires I would connect to the relay.
I would use the selector on the fridge panel to use gas or mains and ignore the 12v.
A suitably rated switch and fuse would complete the wiring.
Is the feed from the relay used by any other function within the van?
Can anyone see any flaws in this idea?

 

[Mr Plodd]

Why bother??
The fridge will only operate on 12v when being towed, which is not going to be for any extended period of time.. Fridge contents stay cool for many hours, I have taken a ferry to Spain and the fridge contents didn't warm up over those 2 days, a 6 hour drove is nothing in comparison. Stop worrying about it, it's not important!

 

[Joggerdude]

Why bother??
The fridge will only operate on 12v when being towed, which is not going to be for any extended period of time.. Fridge contents stay cool for many hours, I have taken a ferry to Spain and the fridge contents didn't warm up over those 2 days, a 6 hour drove is nothing in comparison. Stop worrying about it, it's not important!

1. Obviously the 12v only operates when towing.
2. From experience I know that the fridge warms up quickly when 12v is not working in warm temperature, even over a few hours.
3. It is my view as to whether it's important or not. Don't presume to say that I am worrying about it, I am not. I simply look for solutions.
4. What make and model is your fridge? From the many posts about warming fridges due to failed 12v when towing, I can guarantee there will be many who will want one these remarkable fridges.

 

[Mr Plodd]

I have no idea of your experience or knowledge in regards to caravans, many posters are new to the game. As you joined this forum a short while ago I was trying to be helpful, sorry if I upset you by detailing my fridge "experience" often in conditions of high (mid 20's+) ambient temperature.

 

[Buckman]

On previous vehicles we had the facility to keep the fridge "cool", but found it was not very effective. Consequently we found that by freezing the food prior to journey, the fridge stayed cool all the way from Portsmouth to Zaragoza in Spain. A duration of almost 48 hours. On our current vehicle we never bothered with the facility.

I would be very wary of bypassing anything as that is a modification and the insurer of the caravan needs to be notified.

 

[trevormonty]

Issue seems to be with circuit driving relay coil as its clicking on and off. Most likely low voltage cutoff off coil driving circuit given regular 4sec cycle.. You could bypassing that circuit and try driving coil from car's 12v or house battery. House battery will drive coil for days without an issue.

At some stage I plan to run new van's fridge off house battery while travelling. With draw of 120W the 100AH house battery can run it for 5hrs without going below 50%. In sunny weather the 260W solar panel will extend that by few hours. To protect battery need either low voltage cut circuit or timer. Both of which can be found at Aliexpress. Alternatively use my phone's timer to remind me to turn it off.

 

[Dustydog]

Three Forumites replied to your original post and you never answered back! If we had some answers we may possibly be able to help!

 

[Ferrodo]

My advice ( for what it’s worth)
Buy a good cool box and forget about running the fridge while towing. Too many potential problems with electrics and collapsing drawers due to weight.
Okay people….. fire when ready 🤭

 

[ProfJohnL]

I am always concerned when I see a poster commenting about an appliance, because it does not work, and then telling or asking about modifying it.

We have only the posters written comments on which to judge what competence they may have on the subject, and therefore whether to offer support or tell them to stop because we can foresee practical, safety or legal issues they may not.

But in general it is better not to attempt a modification which takes an appliance or system away from its standard approved design. Whilst you may understand what you have done, will it make sense to anyone who buys or uses it after you.

 

[otherclive]

My advice ( for what it’s worth)
Buy a good cool box and forget about running the fridge while towing. Too many potential problems with electrics and collapsing drawers due to weight.
Okay people….. fire when ready 🤭

If it’s any comfort I did the same and used a Coleman Xtreme cold box, although the fridge did have some pre chilled stuff. in it for en route snacks. But that was all before smart alternators complicated caravanners lives. 😂

 

[RogerL]

My advice ( for what it’s worth)
Buy a good cool box and forget about running the fridge while towing. Too many potential problems with electrics and collapsing drawers due to weight.
Okay people….. fire when ready 🤭

For those with mains power available at home/storage, it's probably best to pre-cool the fridge on mains before loading up - but of course few storage facilities have mains available.

 

[Gafferbill]

......on a forum such a technical problem can only be dealt with by pointing out the most likely scenario.
The fact that the fridge works on gas and mains voltage is irrelevant.
When you say the car to fridge voltage is 13.8....where are you talking this measurement?
It needs to be taken at the feed wires to the 12 volt element accessible by removing an external fridge vent.
I don't recognise a fridge relay at the front of the caravan but there will be a dedicated 12 volt fridge fuse in this location.
There is a relay on the circuit board at the back of the fridge and this can click in the manner you describe.
This is indicative of insufficient voltage present to power the 12 volt heating element.

 

[toad a caravan]

Perhaps items that can be frozen are,prior to departure,as mentioned above if you could connect up to mains before that may assist

 

[ProfJohnL]

Its always wise to pre cool the fridge before travelling, either using mains 230V ac or gas. depending on the fridge and conditions it may need to be run 12 to 24 hours before departure.

If mains and gas are not an option, then freeze two or three 4 pint Of 4 or 8, 2pint) plastic milk bottles and put them at the top of the fridge to pre cool the fridge. Removing them before moving off.

 

[Hutch]

I always, pre cool the fridge on gas for 1/2 hour, then change over to electric, ( on the house drive) then Mrs H fills it up, frozen stuff in the freezer, or if just 3 days away, ice for drinks, Thankfully our 12 volts from the car works fine.

 

[Dustydog]

I always, pre cool the fridge on gas for 1/2 hour, then change over to electric, ( on the house drive) then Mrs H fills it up, frozen stuff in the freezer, or if just 3 days away, ice for drinks, Thankfully our 12 volts from the car works fine.

Good point . I suspect very few of us ever use the gas function😥. We should👍

 

[ProfJohnL]

Good point . I suspect very few of us ever use the gas function😥. We should👍

Why?

 

[trevormonty]

Good point . I suspect very few of us ever use the gas function😥. We should👍

We use gas more often than not as unpowered sites are cheaper.

 

[Buckman]

Why?

I think the answer is fairly obvious? Gas is not cheap and EHU is included in the price of the pitch.

 

[Dustydog]

Why?

Use it or lose it.
Best to try it at home like Hutch before a trip. There are occasions when you may be off grid and totally reliant on the gas fridge.

 

[Beardy]

My advice ( for what it’s worth)
Buy a good cool box and forget about running the fridge while towing. Too many potential problems with electrics and collapsing drawers due to weight.
Okay people….. fire when ready 🤭

This is exactly what I've done so far, though I use a couple of cheap cool bags rather than a 'good' cool box. I freeze anything that can be frozen, the stuff that I want to keep frozen goes in one bag and the rest in a second bag along with the chilled stuff (butter, cheese etc.). It's a fair bit of payload weight saving as it travels in the car rather than the caravan.

I used to buy frozen raw dog food mail order, it came wrapped in some sort of thermal stuff, sort of a cross between foam and polystyrene. It must have been in the postal system for 18 hours minimum and always arrived frozen.

 

[Mel]

Why?

Bear in mind that I am not technical, but two different AWS techs have told me that it is a good idea to run the fridge on gas periodically as it stops the burners getting clogged up with cobwebs and debris.
Mel

 

[otherclive]

Bear in mind that I am not technical, but two different AWS techs have told me that it is a good idea to run the fridge on gas periodically as it stops the burners getting clogged up with cobwebs and debris.
Mel

I used to do that for an hour as part of pre cooling the fridge prior to switching to electric for the remainder of its overnight pre cool.