Dometic 3 way fridge - 12 V switch problem

al68 · Feb 25, 2013

Last year the 12V switch was a little erratic. Start up the motorhome, switch to 12V operation and no red indicator lamp to show that it is working. Flick it on and off a couple of times and it would light up and the fridge would cool down nicely.
This year, no amount of switching will get it to illuminate. I don't think it is cooling either but have only done 15 mile runs.
I have done a few tests with the multimeter: There is no 12 volt supply when the engione is off - good. There is a 12 volt supply at the switch when the engine is running - good. Flick the switch but no red light coming on in the switch - bad. I did take the switch off and check resistance; when the switch is off there is indeed no connection through to the supplly pins; with the switch in the on state there is a connection to supply side of switch.
These switches cost £20 so maybe there is more to the switch than meets the eye!
Anyone any ideas apart from buy a new switch which is looking likely.
I am about to try running on 240Volts to see if it cools the fridge. Do the 12V and 240V use the same heater coil in the fridge, anyone know?

Thanks for reading

al68 · Feb 25, 2013

Just for information. Have checked the 240 volt operation and it works. Have also now tested the switch with a 12 volt bulb and a spare battery. The switch does the main switching job ok but the warning light in the switch does not work. I therefore presume the fridge will be cooling!
I have found a source for the switch at a price of about £13 at gwcaravanservices. Its part number 2926273505 in case anyone else needs one!
I wonder if I can replace the warning light bulb?

TonyJones · Feb 25, 2013

Light on ours comes on sometimes, but not always. However, I haven't bothered doing anything about it, as it always cools.
You can test that fairly easily - once you've taken it for even a short run, if you open the icebox you should find the element inside is freezing cold to the touch.

gjh · Feb 26, 2013

The 12v operation isn't always intended to cool the fridge down but, rather, to maintain a low temperature whilst travelling after it has been cooled using gas/mains.
I think the warning bulbs in that type of switch tends to be soldered into the circuit so, even if you could obtain one, the cost may well not be much less and it would be a hassle changing it.

al68 · Mar 16, 2013

Update: Bought a new switch and no change so it's not the switch, I had my doubts! Have run new tests on the switch and neon light does work when connected between poles of an old 12 Volt battery.
I have now gained access to the top and back of the fridge. I disconnected the 12 V heating element and connected it across the 12 volt battery terminal. Left it for 10 minutes and felt it (still in-situ) to check if it was warming. It was very hot!
So switch works and heater element works but not when in the van circuit. I took it for a run of 20 mins and it was stone cold (heating element)
I am now checking out the rest of the circuit to see if there are any bad connections.
Any suggestions welcome. (Taking it to auto-electrician is a last resort - not in my nature)

al68 · Mar 25, 2013

Found the problem. A burnt out connection on the feed from the power distribution board (behind the drivers seat if you have a CI Carioca 644.) Not sure why it got so hot. A poor connection would result in a resistance and some heat. The fuse on the circuit is still intact. Need to do an autopsy on the connectors.
I will replace the pcb board socket and fit a new plug when they arrive from Italy and then run some tests.

al68 · Apr 30, 2013

All working now but keeping an eye on that 12 V control board behind the seat.

katetaylor1 · Jun 3, 2013

Hi, we have another friend in need of your tips on fridges here - a trouble shared is a trouble halved... and that's why forums can be so handy!

Tue, May 28 2013, 5:49AM

Teepee

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Joined: 2012-09-29

The 3way fridge does not work on240 or gas it just won't
cool the pipes behind fridge are hot. I never use the 12v side so don't
know if that works, any advice would be very helpful. Thanks. Teepee.

516yuanyuan · May 16, 2016

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