Dometic Fridge Thermostat not cutting out

[The Raptor]

I have a 2003 Dometic Fridge/Freezer Thermostat Not cutting out on 12v or AC Power !


The Fridge works on LPG, 12v & AC Power.
However when on 12V it appears the Thermostat does Not Cut-Out.


I have tried setting it to the Lowest (warmest) setting, being No.1, and watching the 12V Control Panel, it stays on 6~7A all day long, 7 Amps is approx. 75~80Wh.


The Freezer cools to -23 degrees, the Fridge cools Down to minus degrees if set on the Highest setting.


So, can anyone tell me should the Thermostat Cut-Out the Cooling once it reached a preset temperature ?

[creativepart]

It’s hard to say exactly what your issue is… but you really shouldn’t run a 3-way fridge on 12v. That’s why all newer RV absorption fridges are two way… AC and LP only.

The older 12v option on RV fridges use far too much power and can quickly run down your house batteries.

The reasoning behind using 12v with an absorption fridge was to keep the fridge cold while driving without using LP. The motorhome alternator basically powers the fridge.

I realize this doesn’t in any way address your issue but perhaps you could solve the problem by not ever using the 12v option on the fridge.

Wait, rereading your post… it’s doing this on AC too? Sounds like a temp sensor the fridge’s electric heating element isn’t working.

[Morich]

As a "quickie" there is often a form of thermostat sensor inside the frig near the coils/fins in back. check to see it has not got knocked off and into some spot where it no longer senses the temp?
This not the most likely but it is also usually easy to take a look.

For the best info, if you can locate a model number of the frig, we can then do a search for troubleshooting info that really cuts the guessing!

Kind of like trying to start a car? It helps to know if it is a Ford or VW, so you can know where they put the engine?

[creativepart]

Richard... lots of different stuff on the OP's RV... he's in Austrailia and it's a model RV we've never heard of before.

On top of that... his AC is 240v not 110v.

So maybe we will and maybe we won't have any info on his Dometic fridge

[bigb]

Yes the thermostat (called a thermistor) should be regulating your temp on gas and 230. On 12 volts it does not , it's just on all the time as it is assumed you will be using 12 volts only while driving and the wattage of the 12 volt element is low and it is only intended for maintaining an already cold fridge. Like Creativepart mentioned, it is not intended to run on 12 volts when parked/camped.

If you supply your model number I have manuals for most of the Dometics.

Re read your post again, if it is not cutting out on AC power then check the thermistor position on the fin, it should be firmly attached. Sliding it up and down can also have quite a large effect. If the thermistor is bad look into a snip the tip replacement https://www.snip-the-tip.com/cgi-bin/articca.cgi

It's a bit confusing if you mean the thermistor is not cutting out on 12 volts, or 12 volts and 230 volts both. Do you mean you are running it on 12 volts while plugged into the mains? Or it's not cutting out when running the fridge on the mains?

[The Raptor]

Hi Guys,

I made an error, the 12V 18Amps & 240V Power draw is 1.4 Amps.

I tested the AC & DC Elements over the last few days & had the Temperature setting on 2.3 and the Freezer gets to -23ºC, the Fridge get to Temperature 4.3ºC & Stays there.
I have never seen the Amp meter on the DC Control Panels Switch OFF, it is harder to see if AC Thermostat Cuts out as it is drawing 1.4A & I have the TV & Computer on.
I am thinking AC & DC Use the same Heating Element, but Not sure.

I tested these on the Onboard 12/240V, 150W Inverter, operating off the ample Battery Energy, Not State Grid.

When I turn the Temperature knob on the Fridge down to 1 or less, on both AC & DC, I hear a relay clicking sound, but On DC, the Control Panel does Not reduce from 18A, it appears to remain ON, only when I change to AC or LPG, the DC Control Panel Draw drops to 1A, as I have LED lights on.

As for the Fridge Temperature Probe, I can see what looks like a tiny 3mm aluminium pipe coming through from the rear wall of the fridge & goes between the Fins in the Fridge, & has a U shaped Aluminium cover securing it to the rear of the Fin Plate with a Screw.

NB: Besides the onboard 2x 100Ah 12.8V LAB (2.56kWh), I actually have connected up 3x 12.8V LiFePO4 (3.84kWh) Batteries in Parallel, giving me a Total of 6.40kWh of Energy Storage.

So, 12V is on for 24hours (18A x 12V =216W per hour, x 24hours should only consume 5.18kWh of Energy, and that is not taking into account the one 500W Solar Panel & two 20 year old Amorphous Panels on the Roof are charging the Bank of Batteries there is ample Energy for operating the Fridge all Day.

The Fridge Model: RM4601

[Morich]

With the correct manual and correct step by step procedure for the right model, you can begin to isolate the problem.
We can only guess what different parts your frig may use due to the different voltages involved, so what you are getting are just random numbers which mean nothing until we can say what causes those numbers!

For the controls, we can guess there is some form of temperature sensing and likely what you have found inside on the fins. There are procedures like sticking the thermostat in cold water for testing the operation but we would need to know what is recommended for YOUR RV, not what we have used here.

Using an ohmmeter to look for it to open and close at the correct times/temperatures is fairly simple but it has to be done in the correct way for the model you have.

[bigb]

I'm not understanding what you are looking to fix, everything looks to be operating as designed. The AC element and the DC element are not shared, they use different elements.
As I mentioned in my first reply, when on DC there is no regulation, it runs all the time as it was never intended to be used unless you are driving and supplying a constant charge. The 12 volt mode will cut off and go to gas (If you have AES) if battery voltage drops below a certain threshold.

[bigb]

I didn't have your service manual but a quick Google search turned up an owners manual: https://www.dometicrvcentre.com.au/d...nager/item/130

Note page 4 where it states there is no thermostat function on 12 volts, and to only use 12 volts when the vehicle is running. It also repeats this under "Regulating the Temperature". If you want to run a 12 volt refrigerator for extended periods on your setup you would be far better served by a 12 volt compressor fridge with a Danfoss compressor, it will run on a fraction of what it takes to power a resistive heating element, and it will cycle on and off as needed.

[The Raptor]

Originally Posted by bigb

As I mentioned in my first reply, when on DC there is no regulation, it runs all the time as it was never intended to be used unless you are driving and supplying a constant charge. The 12 volt mode will cut off and go to gas (If you have AES) if battery voltage drops below a certain threshold.

Thanks Bryan,
Sorry, I must have misread, that clears my Mind, thanks for clarifying that.
It actually appears to Cut-out when using the 240V on-board Inverter when Operating on Batteries.

I assume AES is Automatic Energy Select ?

It is a learning curve getting to understand all the workings of the Beast, I fixed a Jet on the LPG water heater yesterday as the Flame was Flaming in the Tube, not inside the heater, discovered a Tar substance was partially blocking the main Jet.
Now I have to move onto fixing several Leaking Water pipes.

[bigb]

Originally Posted by The Raptor

Thanks Bryan,
Sorry, I must have misread, that clears my Mind, thanks for clarifying that.
It actually appears to Cut-out when using the 240V on-board Inverter when Operating on Batteries.

I assume AES is Automatic Energy Select ?

It is a learning curve getting to understand all the workings of the Beast, I fixed a Jet on the LPG water heater yesterday as the Flame was Flaming in the Tube, not inside the heater, discovered a Tar substance was partially blocking the main Jet.
Now I have to move onto fixing several Leaking Water pipes.

Yes, automatic energy selection. Which you can over-ride and force any one mode.
Your fridge will regulate when you run it on the inverter from the batteries since the fridge is now running on 230V and has no clue that the 230AC is originating from the batteries, however this is even less efficient than running on 12 volts as you are now losing efficiency through the inverter, although the cycling may make up for some of this. Think about your expensive batteries too, deep cycling even lithium batteries will reduce their life. Not a big deal for occasional camping as lithiums have so many more life cycles than lead anyway but if you are living in it 365 days/year your added cost of replacing batteries sooner might outweigh your savings over just running on AC or gas. It takes very little gas to run an absorption fridge.

[The Raptor]

Originally Posted by bigb

Think about your expensive batteries too, deep cycling even lithium batteries will reduce their life. Not a big deal for occasional camping as lithium's have so many more life cycles than lead anyway but if you are living in it 365 days/year your added cost of replacing batteries sooner might outweigh your savings over just running on AC or gas. It takes very little gas to run an absorption fridge.

I import Lithium-IRON LiFePO4 (LFP) Batteries, we do NOT use or recommend Lithium-ION Batteries, as the "ion" are a lot more Dangerous at Runaway (Catching on Fire) when being Charged.
TESLA Vehicles use Lithium-ion, we call them Cave-Man Lithium Technology !


It is a Myth that LFP are Expensive, unless someone is adding Big profits onto them.
We sell LFP for approx. AU$500kWh (US$300kWh), AU$400 if you order 30kWh.
LAB are approx. half that Cost, however Quality LFP Cells have 6'000 cycle life @80% DOD, Not to mention less that Half the Weight.

[bigb]

Originally Posted by The Raptor

I import Lithium-IRON LiFePO4 (LFP) Batteries, we do NOT use or recommend Lithium-ION Batteries, as the "ion" are a lot more Dangerous at Runaway (Catching on Fire) when being Charged.
TESLA Vehicles use Lithium-ion, we call them Cave-Man Lithium Technology !


It is a Myth that LFP are Expensive, unless someone is adding Big profits onto them.
We sell LFP for approx. AU$500kWh (US$300kWh), AU$400 if you order 30kWh.
LAB are approx. half that Cost, however Quality LFP Cells have 6'000 cycle life @80% DOD, Not to mention less that Half the Weight.

Yes I did mean LiFePO4 but I just get tired of typing it out every time.
So if you are well experienced in LiFePO4 you could be a lot of help here. Some of us, myself included, are making the plunge to LiFePO4 and I for one am overwhelmed with the huge number of available brands and wide price variations. Also not sure what to look for exactly in terms of the BMS and cold weather-hot weather protection.

[The Raptor]

Originally Posted by bigb

Yes I did mean LiFePO4 but I just get tired of typing it out every time.
So if you are well experienced in LiFePO4 you could be a lot of help here. Some of us, myself included, are making the plunge to LiFePO4 and I for one am overwhelmed with the huge number of available brands and wide price variations. Also not sure what to look for exactly in terms of the BMS and cold weather-hot weather protection.

95% of the Micro Power Grids we sell go to Rural people who are sick of getting Stitched-Up the the State Grid supply Charges, as the AU$30 Monthly charge, means Presumer's need to Gift 375kWh of Energy per Month (12.5kWh Day) to just eliminate that Cost if getting an 8c per kWh FIT !

However, for older RV's Inverter will commonly be 12V like my Beast, so will require 12.8V LIFePO4 Batteries connected in Parallel.

LiFePO4 Batteries need to be configured to Match the customers Hybrid Inverter, Voltage!
Commonly 12.8V, 25.6V or 51.2V, as with Modern Inverters an Extra Cell (3.2V) greatly assist with the Initial Hight Start Power Draw of most Equipment like French Oven (Microwave) & Coffee Machine etc.


I am yet to Replace the original on-board 1.5kW (1500W),12v/240 Hybrid inverter with a 5kW (5'000W) 48V LUX Hybrid inverter, and simply use a readily available 48V~12V Voltage Converter to feed into & operate the 12V RV System.
The image below is 12~24V & used to Power the DART unit's 24V Motors, so they Turn Quicker.