Advice on 3 - way fridge running on 12v

I have a Jayco Swan off-road camper trailer (2011) that has a Dometic RM2350 3-way fridge installed.
The fridge works well on gas and 240v (provided it is reasonably level, particularly on the side to side axis). However, I have problems maintaining fridge temperature when on 12v while travelling. If I start the travel with the freezer at -18 to 20 oC it will be down to -5 oC or a lot worse at the end of the day. Other travellers I have spoken to on the road say their fridge holds its temperature when travelling but set ups and fridges vary enormously.
The fridge is wired directly to the van’s 120 amp/hour battery, which is charged by the tow vehicle (Mazda BT50) through an Anderson plug connection. I have a 12v fan at the back of the fridge to dissipate heat.
I am going to have to modify the wiring to introduce a switch to cut the supply from the battery when the vehicle is turned off because being a pop up and out van it is an effort to get at the fridge to turn it off unless the van is set up.
There has been so much written about fridges and wiring on forums that it becomes a bit confusing. It seems to me that I need to check the voltage drops to ensure wiring from the tow vehicle to the van battery and from the van battery to the fridge indicate cabling is adequate and if it is then my options are:
1. Forget about running the fridge while driving and ensure it is fully stocked and cold when heading off.
2. Run the 12 v to the fridge directly from the tow vehicle through the Anderson plug (this would solve the potential van battery over-draw problems)
3. Keep the existing set up as it is sensible but introduce a motion switch into the line to fix the potential battery over-draw problem

I would appreciate any advice from more experienced travellers
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Reply By: Batt's - Tuesday, Apr 16, 2013 at 02:51

Tuesday, Apr 16, 2013 at 02:51
It's a fact that 3 way fridges are not very good when travelling especially in hilly areas and yes they do not maintain a CONSISTANT temp when travelling because they need to be level to operate efficiently. Upgrading the wiring won't usually help I've tried that one. You just get use to it especially in hot weather when I use to stop for fuel or site seeing I ran it on gas. 3 ways just can't compete with 2 way compressor fridges they don't perform very well on hot days the are very very power hungry you will get approx less than 2 hours out of a battery then it needs charging and about 2 to 3 days out of the same battery with a 2 way compressor fridge and they will operate up to a 30deg angle so travelling doesn't worry them and they are cheaper to buy. If I ever get another van I would replace the 3 way with a Waeco Coolmatic upright set up dual batteries and solar panels with a batt monitor and have trouble free touring and only use gas for cooking.
AnswerID: 509104

Follow Up By: Charlie B2 - Tuesday, Apr 16, 2013 at 13:15

Tuesday, Apr 16, 2013 at 13:15
WHOA, Batt's!

Sorry to hijack the thread, Paul, but I REALLY, REALLY, hope Batt's didn't really mean what I read above, about running his fridge on gas when you stop for fuel !!!!!

If by any chance anyone is running ANY gas appliance with a pilot light, PLEASE, PLEASE PLEASE TURN IT OFF before you enter a service station driveway - that includes going anywhere near kerbside pumps in country towns.

OK, fine idea for when you're sightseeing or buying the groceries or veggies, but fuel - that's an absolute NO-NO! If you've got into that habit, it's one I'd be getting out of before your insurer finds out the risk you've been taking!

Different story, of course, if you meant something other than my interpretation, but if not, respectfully, I'd rather you were fueling up ANYWHERE except where I'm doing the same thing.


FollowupID: 786821

Follow Up By: Batt's - Wednesday, Apr 17, 2013 at 19:31

Wednesday, Apr 17, 2013 at 19:31
Sorry should have said after fuelling when you park to the side and go back in for a bite to eat hope I didn't cause a big panic
FollowupID: 786990

Follow Up By: Charlie B2 - Wednesday, Apr 17, 2013 at 20:50

Wednesday, Apr 17, 2013 at 20:50
Hi Batt's,

Maybe not a big panic, but you certainly caused me a few palpitations for a while, there! :-)

I do feel much more comfortable now that you've clarified your earlier post - even I can live with that qualification, provided you're far enough away from the vapour source and the weather is cool enough and there's enough breeze blowing in an appropriate direction to ensure that petrol or LPG vapour can't get anywhere near your pilot light.

Maybe I'm being a Nervous Nellie, but quite a few years ago a friend had a petrol can, with the cap off, explode on a hot, still day from a flame more than 50 feet away - the burning vapour flashing past scared the daylights out of him. He was really lucky he wasn't still bending over the can!

And I was living in Sydney for a short time 44 years ago when a servo went up, reportedly from some clown smoking while filling a vehicle with petrol. (For younger readers, servo staff used to fill up vehicles once upon a time, and check your oil and wash your windscreen, all free of charge, when petrol was 33c per GALLON) Can't remember now whether he and the vehicle owner got out of that or not, but driving past while it was burning certainly left a lasting impression!



FollowupID: 786997

Follow Up By: Batt's - Thursday, Apr 18, 2013 at 20:07

Thursday, Apr 18, 2013 at 20:07
A couple of weeks ago at a servo I was walking inside to pay the car beside me in the middle isle had a flat battery someone wheeled around in front popped the bonnet started to hook up the jumper leads the servo attendant went into panic mode fumbled the loud speaker mike then was able to turn it on and yelled at them to stop and get of the floor the look on her face when she turned to me was shear horror.
FollowupID: 787075

Reply By: Sand Man (SA) - Tuesday, Apr 16, 2013 at 07:26

Tuesday, Apr 16, 2013 at 07:26
Yes, the 12v operation is only to maintain fridge temperature while travelling.
Trying to maintain the freezer temperature is probably beyond the physics of 12v operation.

As far as the van battery is concerned, you may need the inclusion of a dc-dc charger at the van end to boost any voltage drop back to what is required to charge the battery from the vehicle alternator.

Keep in mind, the 3-way fridges running on 12 volts consume a lot of current and prolonged stoppages during the day will not do much except drain the battery.

The best solution is to add the dc-dc charger, then replace the Dometic fridge with an upright compressor fridge that runs on 240vac or 12vdc. Both Waeco and Engel have upright models available. If you have a dc-dc charger with a solar input port (such as the Ctek D250S dual), you can maintain a charge in the battery at camp.

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AnswerID: 509109

Reply By: Member - John and Lynne - Tuesday, Apr 16, 2013 at 08:44

Tuesday, Apr 16, 2013 at 08:44
From our experience it is always worth checking that the fridge has been properly installed with sufficient insulation packed in around it. It made a huge difference to the fridge in our previous van which had your problem when proper insulation was installed and the baffles adjusted. Our current properly installed 3way fridge travels well even for a long day. In hot weather we turn it to gas when we stop for lunch etc. Is yours a T Rated fridge suited to hot weather? Lynne
AnswerID: 509112

Reply By: Member - Frank P (NSW) - Tuesday, Apr 16, 2013 at 10:30

Tuesday, Apr 16, 2013 at 10:30
Hi Paul,

We had a 3-way in a new Avan camper. It never worked very well on 12V because the wiring in both the tow vehicle (done ny an auto sparkie) and the van (done by the factory) were simply inadequate.

We fixed it by installing an isolator in the tow vehicle and heavy wiring (6B&S) from the battery to the isolator and then to an Anderson at the rear of the tow vehicle.

We also installed 6B&S wiring from the Anderson on the van to a DC-DC charger for the van battery.

We installed a relay so that when the tow vehicle was running the 12V to the fridge came from the tow vehicle, and when stopped it automatically switched over to the van battery.

We upgraded the cabling in the van from the battery and the relay to the fridge. From memory we used 8B&S for that as they were short runs.

After that it worked quite well on 12V - not as good as 240 or gas, but as well as it was ever going to work on 12V.


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AnswerID: 509116

Reply By: ozjohn0 - Tuesday, Apr 16, 2013 at 10:40

Tuesday, Apr 16, 2013 at 10:40
You could bypass the battery and take power direct from the tow vehicle via the Anderson plug or fit a DC - DC charger.
Google 'Fridge Switch' as they're easy to install and work very well. They're a motioon detector switch that fits at the bottom rear of the fridge and only supplies power when the van is moving.
Also don't expect a 2350 fridge to work well in hot weather not matter how well its installed or insulated as it only has a 'ST'climate rating.
AnswerID: 509117

Reply By: Paul J11 - Tuesday, Apr 16, 2013 at 11:48

Tuesday, Apr 16, 2013 at 11:48
Thanks all for sharing your experiences and advice. A compressor fridge sounds better but I'll have to stick to the 3-way a bit longer because of the cost. Will check out the insulation, wiring and look at the DC-DC charger.
AnswerID: 509121

Follow Up By: TerraFirma - Tuesday, Apr 16, 2013 at 13:37

Tuesday, Apr 16, 2013 at 13:37
Hi Paul, One thing I have noticed is that there are now more compressor fridges available than ever before. You don't need to pay a premium for Waeco or Engel, there are so many choices now, most use reputable compressors such as the Danfoss or Japanese types. Gas Fridges are great long term solutions, you don't need 12v power and they use little gas etc.
FollowupID: 786829

Reply By: David16 - Tuesday, Apr 16, 2013 at 17:43

Tuesday, Apr 16, 2013 at 17:43
We had a 2010 Swan Outback as well, best advice is dump the 3 way and get the upright Engel 2 way which is same size and slots straight in. You can run it whilst driving and drawers low amps and hold regular temp! We also had same fridge in our Ultimate Camper.

AnswerID: 509146

Reply By: traveln round - Wednesday, Apr 17, 2013 at 07:28

Wednesday, Apr 17, 2013 at 07:28
Hi paul.
This is a option for you.i have done this to my fridge both in the jayco stirling when had it and now in the lotus trooper.we are by the sounds like you.when hitting the black top travel a good days.nearly every1 who says there 3way fridge works fine on 12v are normaly traveln for a few hours aday.not saying all here.down in the south its cooler threw winter so any fridge is going to work.up north here bit different.
Even when we brought the jayco the sales person told us that the fridge runs on %20 efficent.
What we have done is run anderson straight off my 2nd and 3rd battery and installed a inverter mounted up behind the fridge threw a fuse and now when traveling fridge is running on 240.keeps everything nice and chilled even after a 10hr day drive up in the top end.when pull up then flick over to gas.if you read specs the fridge pulls round 140 watts so i just run a small 300 watt inverter.
Food for thought and my 2 cents worth
AnswerID: 509193

Follow Up By: Paul J11 - Wednesday, Apr 17, 2013 at 10:16

Wednesday, Apr 17, 2013 at 10:16
Thanks, however, Jayco say that the fridge should not be run on gas or 240v while the van is collapsed because the bed slide and canvas sides lay over the fridge top vent - risk of fire.
I suppose the indication that it is safe to run on 12v in that collapsed state gives an indication of the amount of heat generated by running with 12v and consequently the relative efficiency of 12v - 20% as you say.
FollowupID: 786940

Reply By: TerraFirma - Wednesday, Apr 17, 2013 at 13:36

Wednesday, Apr 17, 2013 at 13:36
Paul makes a valid point and spot on about the efficiency on 12v , the other option is 2 way fridge suggested above or is it practical to keep as is running 12v in conjunction with Techni Ice? If 12v whilst travelling is the issue why not put some frozen Techni ice sheets in until you arrive? Just thinking out aloud as this may not be practical?
AnswerID: 509207

Reply By: Nigel Migraine - Wednesday, Apr 17, 2013 at 20:04

Wednesday, Apr 17, 2013 at 20:04
The problem is that with a 12V supply to the heating element in the fridge it is only necessary to loose (say) 1V and 8% of the energy is lost and that's easy to do in a circuit carrying 12A+. In reality it's worse than this because they don't work very well at just 12V anyway.

The solution is to purchase a small inverter - 300W will be fine - and non sine wave is OK too (but I'd go sine wave 'cause they're cheap these days) and run the fridge from its 240V heating element.

Otherwise three-way fridges are an excellent choice for people who camp in one spot for a number of days, as do I

And... before the, lacking in knowledge, doom-sayers rush to their keyboards to issue dire warnings of the evils of 240V in a vehicle.. I refer you to a thread I engaged in on this site about 12 months ago.

AnswerID: 509224

Follow Up By: Batt's - Thursday, Apr 18, 2013 at 20:20

Thursday, Apr 18, 2013 at 20:20
I had one of the old style 40ltr chess cold camping fridges in the 90's in the back of my 4WD and tried it on my inverter when travelling from newcastle to bris and back on a few occasions to see if it would help it made no difference to my fridge so I just went back to the 12v outlet.
FollowupID: 787076

Follow Up By: oldtrack123 - Saturday, Apr 20, 2013 at 23:17

Saturday, Apr 20, 2013 at 23:17
[Quote]Nigel Migraine replied:
The problem is that with a 12V supply to the heating element in the fridge it is only necessary to loose (say) 1V and 8% of the energy is lost and that's easy to do in a circuit carrying 12A+. In reality it's worse than this because they don't work very well at just 12V anyway.

The solution is to purchase a small inverter - 300W will be fine - and non sine wave is OK too (but I'd go sine wave 'cause they're cheap these days) and run the fridge from its 240V heating element.[end quote]

Since the fridge should only be running when the engine is running ,the RIGHT sizes cable for the AMPS & run length will usually mean the fridge gets around 13V <+ V.

This new craze for inverters is getting ridiculous
Especially the down play on the risks of using them
They can be just as deadly as mains power under a certain combination of faults!!!

FollowupID: 787284

Reply By: oldtrack123 - Saturday, Apr 20, 2013 at 22:53

Saturday, Apr 20, 2013 at 22:53
HI Paul
The essentials for best operation of a 3way are:
[1]Adequate wiring from the TUG battery ALL THE WAY to the fridge with NOTHING else on that circuit
You require the design voltage for them to generate the necessary heat in the boiler
THAT means you require MIN 12V at the fridge terminals WITH THE FRIDGE RUNNING
& the vehicle alternator inputting to the crank battery [medium idle speed]
If you are not getting at least 12V, the CABLES ARE undersized[as usual]
['2]the fridge does draw a high current & should only be on when the engine is running
This can be achieved by either a "Fridg Switch"[motion sensor]or an ignition controlled relay switching the POS line to the fridge.
[3] Very few 3WAYs are installed to the fridg maker's instructions
This particularly includes the ventilation a baffling at the rear to get the best possible cooling air flow through the fridge CONDENSER

If you do a bit of MR GOOGLE search for "3way fridge fans " "3way fridge baffles"
& similar you will see loads of proven methods,
or come back here & I will give more lengthy details
[4]The charging circuit to the VAN house batteries should be an entirely SEPARATE circuit from the tug battery,to achieve BEST charging of the house batteries

[5]A compressor fridge is great IF you have the means of keeping the batteries charged

That needs a lot of consideration & just how much Solar &/or battery capacity you will need depends on your camping style & fridge temp settings
then you have to decide what you would do if a run of overcast /rainy days set in & you got little solar input
But IF you only used powered sites then a comprressor fridge would be excellent

I myself have both & although I have 200W of solar & 200Ahrs battery capacity
I am often glad I have a 3way
Give it a lot of thought !!
AnswerID: 509419

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