Dometic fridge question.

Hi I have recently bought a Jayco outback camper which has a Dometic 3-way fridge.. I have tested on 240v & gas both work fine.. When I tried 12v not much happened so I put a multimeter on the 12V input at the back of the fridge..
Strange thing I can read around 13V when the fridge is on gas or 240v or off but as soon as I select 12v I can see the input voltage drop to zero..

Does this sound normal ?

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Reply By: Nomadic Navara - Sunday, Feb 07, 2010 at 15:04

Sunday, Feb 07, 2010 at 15:04
The voltage will drop a little (depending on the gauge of the supply cable) but that is not normal. You have a bad joint, relay, fuse or earth in your 12 V supply. May even have a cable that is nearly severed through, but unlikely. If there is not at least 12.5 V at your fridge input terminals with the motor running your fridge will not work very well.
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AnswerID: 403110

Follow Up By: ss--ss - Sunday, Feb 07, 2010 at 17:50

Sunday, Feb 07, 2010 at 17:50
Thanks Navara , I'll try trace the fridge cabling back.. its a bit hard in the hawk as it seems to go behind the front boot .. Anyway will check it out
FollowupID: 672623

Reply By: ss--ss - Sunday, Feb 07, 2010 at 19:14

Sunday, Feb 07, 2010 at 19:14
I removed the existing wiring & plugged my Ctek 7000(in supply mode) directly into the back of the fridge & the voltage went to zero ... does this sound like the 12v fridge element is gone ?

Thxs SS
AnswerID: 403148

Follow Up By: oldtrack123 - Sunday, Feb 07, 2010 at 20:58

Sunday, Feb 07, 2010 at 20:58
If the element is open circuited [broken somewhere ] It will not affect the voltage
loosing voltage would normally mean a short circuit possibly in the element.
Depending on size of fridge , element resistance should be between 1 & 1.5 ohms

Turn all power & switchs off then check element resistance @ IT's terminals[@ boiler]
FollowupID: 672658

Reply By: The grizwaulds - Monday, Feb 08, 2010 at 12:12

Monday, Feb 08, 2010 at 12:12
Hi SS,
Jayco put an isolator switch next to the fuse panel (Just looks like a lightswitch) but this needs to be in the on position when running off your anderson plug. The fridge won't work off the built in battery as it would drain it in about 3 hours. The 12 volt will only run off the anderson plug and make sure that you either have a relay/switch or remember to unplug when you stop for any lenght of time or it will flatten the battery in your car.
AnswerID: 403243

Follow Up By: ss--ss - Monday, Feb 08, 2010 at 13:21

Monday, Feb 08, 2010 at 13:21
Thanks Paul,, Makes sense what you what you just said however I would have thought the fridge would have worked when I connected up my ctek battery charge straight into the fridge.. When I conected the ctek into the fridge inputs the ctek supply light turned off & voltage went to zero..

thxs SS
FollowupID: 672729

Follow Up By: Member - Boobook - Monday, Feb 08, 2010 at 13:38

Monday, Feb 08, 2010 at 13:38

Get a battery instead of the ctek. A correctly working fridge will draw 12 - 14 A and your ctek won't cope so it may be normal for it to go to 0V.

Wire the battery DIRECTLY to the fridge connectors and put a 20 A fuse in line. If it really is taking everything to 0V that will blow for sure and in that case there is a short. But you should have blown fuses galore already if that is the case.

Are you aware that many fridges are not wired to the 12v of the camper/caravan. But run on a separate circuit to the trailer plug. Usually to pin 2 ( otherwise known as reverse). They also often have a separate 12v for aux functions to the 12v of the van. This is so they are only powered when the vehicle is connected and engine running.

When you say "connected directly" do you mean right at the connector adjacent to the fridge or directly to the 12v battery terminals in the trailer?

FollowupID: 672734

Follow Up By: Member - Boobook - Monday, Feb 08, 2010 at 13:39

Monday, Feb 08, 2010 at 13:39
Also check to see if your reverse lights on the vehicle go off when you turn the fridge to 12v.
FollowupID: 672735

Follow Up By: The grizwaulds - Monday, Feb 08, 2010 at 15:22

Monday, Feb 08, 2010 at 15:22
Hi SS,

I certainly do not profess any expertise in the field of electrics but simply passing on what I learnt from owning a Jayco myself. They have their own "trickle charger" to the battery but the on board battery doesn't connect to the fridge. The 12v on the dometic fridge works "reasonably" well but it is simply to keep the heating up process at bay rather than cooling anything down. best advice is to run the fridge 24+ hours before your trip on 240v, maintain during travelling via anderson plug ($100 from auto elect. best money you'll spend but make sure they use 6 - 8mm wire) and then if your free camping use gas (these fridges work a treat on gas). They are a good fridge for what they are.

FollowupID: 672746

Follow Up By: ss--ss - Monday, Feb 08, 2010 at 15:52

Monday, Feb 08, 2010 at 15:52
Thanks a lot,,I will give those suggestions a go charger is 7amp so if it's trying to pull 12amps no wonder it shut down... when I said 'connected directly' I meant I removed the lower ventilation vent behind the fridge & plugged it directly into the 12v input in the fridge...

I'm very happy with this fridge but would be handy to also use the 12v whilst driving between sites...

Cheers SS
FollowupID: 672751

Follow Up By: ss--ss - Monday, Feb 08, 2010 at 19:21

Monday, Feb 08, 2010 at 19:21
Thanks Boobook , I did as you suggested & hooked the battery straight into the fridge with a breaker I had.. The fridge ran on 12v fine, it was pulling around 16amps so no wonder the charger shutdown when I connected it. I'm happy the fridge can operate on 240v,gas & 12v !!
I think I'll get some anderson connecters to wire from the car battery to the fridge for when we are on the road..

Cheers SS
FollowupID: 672776

Follow Up By: Member - Boobook - Monday, Feb 08, 2010 at 21:05

Monday, Feb 08, 2010 at 21:05

Next 3 steps to make it cool nicely are

1)Take the fridge right out and then get a couple of insulation batts. Staple them to the sides of the opening around the cupboards and underneath the bench. In other words insulate all around the sides and top of the fridge keeping the back clear of insulation. This keeps your fridge cooler as well as the bench top.

2)Get as heavy wire as possible in the van AND in the vehicle. Those 16 Amps cause a massive voltage drop. something like 6AWG ( not 6mm) would be good, if not 8WG. Wire it to the main battery via a 40A relay that is powered from the accessories.

If you can't run new wires, you can double up the two wires to be the positive ( ie join the black and red wires at both ends and use them as the +12v) and run the - from the fridge to the chassis at the fridge end and at the plug end.

3)get a thermostat fan like this

Doing these changed my fridge while on 12v from warming to about 12 degrees to being able to cool from ambient to about 2 degrees.

I also took out the freezer door inside, now I can freeze stuff in the fridge, even on 12V

Good luck.
FollowupID: 672790

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