Dometic Refrig is acting up - what are my options

slotsavegas wrote:
It has been quite a while since I originally posted my
Problem. Thanks to all who have offered help.
As it turns out, I turned the fridge off for about 1 minute
And then restarted it and it has been working properly on
both gas and electric. Guess it needed to be rebooted
much like a computer.

Good to know what your "fix" was.
Lots of good advice from others.There is always something to learn
from the forum.

It has been quite a while since I originally posted my
Problem. Thanks to all who have offered help.
As it turns out, I turned the fridge off for about 1 minute
And then restarted it and it has been working properly on
both gas and electric. Guess it needed to be rebooted
much like a computer.

bstark wrote:
The cooling vanes in the top of the food cabinet are responsible for simply convection cooling the air inside the fridge which will tend to drop into the bottom of the cabinet so the 'D' cell battery fans fans you are hearing about simply help to push that cooler air around the food items in the fridge to help equalize temps throughout the cabinet.

Air is the worst item to try and cool so an empty or only partially full fridge is going to work harder to stabilize itself at colder temps.

Some easy-peazy steps you can check before spending a lot of money.
If you are good with a volt/ohm meter, the thermistor clipped to the vanes should show a specific range of resistance measured in ohms and if you research that (I've forgotten so verify please but 8500 ohms rings a bell), you can check it by putting it into a tea-cup full of hot water to observe resistance readings changing with the meter.

The termsitor reacts to warmer air by changing it's resistance as it warms up to trigger an "on" so therefore the higher up on the vane into the warmer area at the top of your food cabinet, the more frequently it should cycle the heat source to your fridge boiler to come on.

If your fridge is installed in a slideout, the air circulation has to make two right angle turns as it enters the rear outside bottom grill, rises up past the cooling fins of the transfer unit at the top pf the fridge and then exits out the upper outside grill, this is less efficient than a fridge with a roof mounted exit vent so sometimes fans are installed in that space behind the fridge to accelerate convection air moving up the rear of the cabinet. The trigger for that/those fans will be a pot (about the size of a nickel) mounted to one of the transfer coil fins with sheet metal screws at the very top of the rear of the fridge inside that upper outside grill.

That pot will likely be marked with it's 'temperature on' rating and will likely be in the neighbourhood of 130-140F. This can also be checked using the same method with a cup of hot water and ohmmeter to see if you get continuity across the leads after you heat the pot up to it's rated temperature.

These evaporative brine solution fridges work well for a time but can very suddenly simply start to fail for a variety of reasons with very little control by you to prevent it.

Propane operation is the most efficient heating source for the boiler BUT the exhaust from the propane burner at the very bottom of the fridge goes up through a chimney tube in that same cavity behind the fridge so if parked with direct sunlight on that side of the RV you can only imagine what kind of temps the rear of the fridge is experiencing.

A 12v pancake fan, preferably two, mounted about halfway up that cavity aimed upwards will make a huge difference in the amount of cooler air drawn in the bottom grill and over that transfer coil at the top of the fridge along with helping to push out the exhaust heat from your propane burner heating the brine solution. Any DIY handy person can mount two of those on a circuit pulled from the fridge circuit board 12volt supply and protect the board with a 3 amp fuse with that aforementioned pot mounted to the fin at the top in series with the fans. That will make their operation automatic and also protect the board.

bstark did a tremendous job outlining the basics. Excellent! And I agree that if you get ohm resistance between 8,000-9,000 the thermistor is working properly.

Sometimes in hotter climates though, when you push the thermistor adjuster up to obtain more cooling you can risk the coils frosting/icing over. If that happens then all cooling is lost at that point and you have to shut the unit down to defrost it. The Fridge-Fix (see website URL I listed above) solves that by sending air over the coils to eliminate the risk of icing and as a result more efficient cooling inside the RV fridge. There so happens to be an article on this new product in the latest issue of Trailer Life.

Gene

The cooling vanes in the top of the food cabinet are responsible for simply convection cooling the air inside the fridge which will tend to drop into the bottom of the cabinet so the 'D' cell battery fans fans you are hearing about simply help to push that cooler air around the food items in the fridge to help equalize temps throughout the cabinet.

Air is the worst item to try and cool so an empty or only partially full fridge is going to work harder to stabilize itself at colder temps.

Some easy-peazy steps you can check before spending a lot of money.
If you are good with a volt/ohm meter, the thermistor clipped to the vanes should show a specific range of resistance measured in ohms and if you research that (I've forgotten so verify please but 8500 ohms rings a bell), you can check it by putting it into a tea-cup full of hot water to observe resistance readings changing with the meter.

The termsitor reacts to warmer air by changing it's resistance as it warms up to trigger an "on" so therefore the higher up on the vane into the warmer area at the top of your food cabinet, the more frequently it should cycle the heat source to your fridge boiler to come on.

If your fridge is installed in a slideout, the air circulation has to make two right angle turns as it enters the rear outside bottom grill, rises up past the cooling fins of the transfer unit at the top pf the fridge and then exits out the upper outside grill, this is less efficient than a fridge with a roof mounted exit vent so sometimes fans are installed in that space behind the fridge to accelerate convection air moving up the rear of the cabinet. The trigger for that/those fans will be a pot (about the size of a nickel) mounted to one of the transfer coil fins with sheet metal screws at the very top of the rear of the fridge inside that upper outside grill.

That pot will likely be marked with it's 'temperature on' rating and will likely be in the neighbourhood of 130-140F. This can also be checked using the same method with a cup of hot water and ohmmeter to see if you get continuity across the leads after you heat the pot up to it's rated temperature.

These evaporative brine solution fridges work well for a time but can very suddenly simply start to fail for a variety of reasons with very little control by you to prevent it.

Propane operation is the most efficient heating source for the boiler BUT the exhaust from the propane burner at the very bottom of the fridge goes up through a chimney tube in that same cavity behind the fridge so if parked with direct sunlight on that side of the RV you can only imagine what kind of temps the rear of the fridge is experiencing.

A 12v pancake fan, preferably two, mounted about halfway up that cavity aimed upwards will make a huge difference in the amount of cooler air drawn in the bottom grill and over that transfer coil at the top of the fridge along with helping to push out the exhaust heat from your propane burner heating the brine solution. Any DIY handy person can mount two of those on a circuit pulled from the fridge circuit board 12volt supply and protect the board with a 3 amp fuse with that aforementioned pot mounted to the fin at the top in series with the fans. That will make their operation automatic and also protect the board.

Depending on your model there is usually some method to adjust the temperature. If there is no knob, setting etc. then there will most likely be a temp sensor inside the fridge near the side towards the back attached to the vanes. It can be slid up or down to make the fridge warmer or colder.

I am in AZ and when temps are over 100 its difficult to get the fridge below 45. After sundown it will cool to normal 35-38.

If the fridge is filled with solid food items it stays cool through the day. If filled with liquids (beer, soda, milk etc) it will do considerably better.

Another option is the Smart RV Products Fridge-Fix. This is a unit that is installed close to the cooling fins and tied into the RV Fridge (Dometic or Norcold)power and does a fantastic job of circulating the inside air - much better than those small battery powered fans. I have one on my Dometic and it does a great job particularly in the Texas heat.

The web site is www.smartrvproducts.com

Gene

I had a similar problem last January with our Dometic fridge /freezer, it stopped getting cold as usually all of a sudden.After alot of research & troubleshooting I replaced the circuit board located in the panel behind the fridge and that fixed it.The board cost aprox $111.00 shipping incl.

The unit works/cools better than ever now.

2006 Dodge 3500 DRW 4x4 LB QC 48K miles
2007 Mountaineer XPS Ribs
2000 Lance 1130
2 Camping Collies (always ready to go)

If your refer is in a slide out there may be two fans that help vent it. If one fails you will have issues. If two fail you definitely will have issues.

Also check your drain tube. Very important that it is not cracked. If it is warm air can enter and cause similar issues. In some setups the tube should have water in it as a drip loop to keep air out and let condensation out as well.

A refer that chases the out-side temperature is improperly vented or has a weak cooling unit.

Seeing as how this fluctuation in food section temperature is a new issue.......sounds more and more like a blockage has occurred in cooling unit between low temp evaporator (freezer) and high temp evaporator (food section).
Provided there is no obstruction of air flow across cooling unit...insulation fallen down etc. But with OEM fan and and another fan blowing doesn't sound like air flow is the problem.

Remove thermistor from clip (on fin in food section) and let it hang down towards bottom of food section. This will force cool fridge and maybe get you thru your trip.

Swap to a household fridge and have cold freezer and fridge at all times.