Dometic Fridge not getting cold

[owlandfox]

UPDATE: July 13, 2018.

Camper at oldest son's house on a level driveway. Slides out. I've been working on putting one or two additional fans near the top of the fridge (heat exchanger fins).

The additional piece of wood that covers 2/3 of the top vent hole confuses me. I know its there to baffle the airflow of the existing single fan. It must at some level work, but with that wood covering 2/3 of the hole, there is only one set of vents that actually vent out the hot air. And the area up there is only partially covered in insulation. I'm going to fill the area in with 2" thick foam to take up the air volume.

So now, my thought is to put 2 120 MM computer fans (1500 rpm) and mount them at an angle. I'd attach them to the wood that partially covers the vent hole; pointing them to blow on the heat exchanger fins; hopefully forcing the hot air to escape out the set of upper vents. There is just 1/4" of space between the fins and the "partial wood covering".

Pictures tomorrow. I just amassed the tools and equipment I need to try this out.

Any ideas on the "partial wood covering" would be greatly helpful.

remember, Roo 23IKSS, fridge in the slide.

Fair Winds to all!

[rockfordroo]

There are ventilation and vent area requirements in the attached document.

UPDATE: Just checked and saw you had a DM702. You should have gotten a similar document with your rig.

[5picker]

Do not mount the fans to blow on the fins unless you somehow mount them UNDER the fins. Blowing from the upper vent back towards the fins will defeat the natural flow of heat rising. Maybe I misunderstood your thoughts?

I left the wood baffle in place and cut a hole in it, the size of my added computer fan, to blow air OUT the upper vent. I mounted the fan directly to the wooden baffle.

I placed my fan off to one side of the baffle with the thought of adding a second fan (on the baffle) but found one fan to be enough. I also added a smaller computer fan on the bottom (horizontally) blowing up over the back of the fridge.

Remember... you don't need gale force winds back there... just enough movement to exchange the air in the compartment.

[snatch]

I cut out a portion of that wood baffle about as tall as those 120 computer fans and mounted them to the remaining wood via the two bottom screw holes in the fan housing. I placed those pulling air from inside blowing it out.
I also put 2 fans inside the bottom vent blowing upward and my fridge is doing much better.

[george6robles]

First check your level. Needs to be level to work properly. Then check access compartment for something blocking cooling fins like a bird nest. Some RV fridge are mounted in slide out and don't have a proper roof vent. These types of setups need more air flow. Some are not built in right. Talk to RV manufacturer there. Usually vents are not boxed in right or heat is not directed correctly in a "convection functional way". Some mount fans to help airflow over cooling fins (backside of fridge near top of cooling unit).
If same issues on propane as the AC electricity and get same issue, then likely not the electrical heat element.
Thermostat/thermistor is what tells cooling unit controller to turn on.
And is likely why you had issues in first place.
You said you fixed the clip, closer to top is colder, and warmer to the bottom. It should be attached via a clip to the first fin in refrigerator section.
Fridge takes 24,hours to cool itself to proper temp. I add cold food and a small fridge fan that runs on 2"D" batteries. I don't like the blue one that much, and prefer the one that has a squirrel cage fan and order absorbing packet. Costs about $5 more then other, but is much easier to put in batteries then the blue one. Get a good thermometer, as a lot of the times it's actually the thermometer that's reading the temp wrong. Use more then one to confirm your temps.

I tend to pack/overfill RV fridge on my family camping trips.
I use a mini fridge for drinks in my outside kitchen, and food stays in the RV fridge. Which can't the constant opening and closing for drinks all day. My guess is you're trying to compare a house fridge to an RV fridge. House fridge uses a motor, compressor, and refrigerant to cool. Makes a lot of noise and can be damaged/life span shortened by road vibrations. RV fridge, designed for the road, made from steel, takes heat and some elements, from periodic table of elements, to cool/freeze your food silently with no moving parts. Sometimes this is how you know if you have a fancy hotel room. You don't hear the fridge running.
Silent operation is critical for some people's sleep. In the RV, you can hear everything.

Some may add a solar powered fridge vent/fan to RV fridge to improve performance along with fridge fan for inside unit.

Can start with warm drinks and end up with cold ones, but takes much longer then a compressor powered fridge. This unit works on convection to circulate temperature. Add a fridge fan from a RV parts store and will see a big difference in temp uniformity and speed of cooling.

Absolutely the worst case scenario I can think of at time, is your cooling unit may have a high-pressure leak in cooling unit. If running, do you smell ammonia? See yellow deposits on cooling unit? May need to remove access covers. If your not comfortable with troubleshooting, then go to RV shop and if new, warranty should have you covered. Or if you have a warranty plan for your used RV.

Want to know more?
See Ford's RV refrigeration. Have many videos on YouTube. Will find me on there too. Hope it helps.

God bless.

Regards,
George.

[owlandfox]

Originally Posted by 5picker

Do not mount the fans to blow on the fins unless you somehow mount them UNDER the fins. Blowing from the upper vent back towards the fins will defeat the natural flow of heat rising. Maybe I misunderstood your thoughts?

I left the wood baffle in place and cut a hole in it, the size of my added computer fan, to blow air OUT the upper vent. I mounted the fan directly to the wooden baffle.

I placed my fan off to one side of the baffle with the thought of adding a second fan (on the baffle) but found one fan to be enough. I also added a smaller computer fan on the bottom (horizontally) blowing up over the back of the fridge.

Remember... you don't need gale force winds back there... just enough movement to exchange the air in the compartment.

Update: 7/14 @ 1500.

Funny how things change in life.

So, yes, my original thought was to put two 120 MM fans below the fins and blow onto them and somehow force the hot air out of the vent.

Once I started measuring and drawing it out, I didn't have the space between the back of the fridge and the baffle to mount the fans / less than horizontal. I could mount them directly to the baffle. That is an ingenious idea! Thanks!

What I did.

1. I changed the thermistor. It was that odd one that only just came into the fridge, made a 90 degree and stopped. I ordered a new Thermistor Kit from Dometic (McGeorge's in Richmond) and imagine my surprise when the the new thermistor came with a plastic slide piece for the fins! New one is in place now.
2. In pulling the fridge I had gouged, not bad, but had gouged the aluminum foil wrapper on the bottom of the fridge. Just added some IBM aluminum tape and it looks like it was straight from the factory!
3. With my fridge in the slide, I added some foam in the upper part of the fridge area to better drive the hot air flow. I added aluminum tape to all foam and took up a decent volume of space. I am sure that was allowing heat to gather and stagnate.
4. I pushed fridge back into place, hooked everything up.
5. Now I'm testing. 85 degrees to start, 1500 for time. 89 degrees outside.

I did try to call Dometic. I was 22 in the queue, so I'll call much earlier in the day next time.

We've checked the usual things. level, no hot stuff in fridge, let it cool for more than 24 hours, don't over stock the fridge, etc.

Thanks for the info on the fans though. I bought 2 120MM computer fans. 1500 rpm. I did fighters in the Navy, those fans didn't even get to flight idle! But if I don't need a wind tunnel in that area, then I'm good.

Next report at 2000.

Fair Winds to all and thank you all for information.

[owlandfox]

2000 Report:

1. After 2.5 hours, the fridge had not cooled at all
2. The freezer did get cold
3. I got mad, pulled the thermistor from the fins to the 3rd tray and I just laid it on the shelf
4. 2030: I now have 62 in the fridge and falling

Not sure what this all means, but I'm letting the fridge run 24 hours and just monitoring every couple of hours.

More Sunday morning!

[george6robles]

Thermistor position.
So sounds like all good now except for the thermostat/thermistor position. I would stick with original. And then just rotate in position if possible. Like pointing down or up or to the side. Or bad control board.

In my mind would think that setup is a new one not meant for fins but it's new position in middle. Resistance is what I would check at different temps. If both the same, then you may have a controller issue.

See how to bypass control board on YouTube. Look for Ford's RV refrigeration on YouTube. Have video showing how to check your fridge. If near hespria CA, I can help in person.

In 24hours you should get freezing temps in fridge.
Please see those videos on YouTube. They do rent some now for pro and diy. But this test will tell you bad cooling unit or not.
The position of the sensor could be correct for a new design that I have not had the experience yet with that particular model.
Should have received a manual in your packet of stuff when purchased.
You will find info there about options for fridge temp.

Update:
Just went looking for the manual I believe you should have.
Temp is adjusted via the control panel. Press temp button repeatedly till desired temp number. 1warmer while 5 is the coldest. This will show on the small digital display on the top right corner of the unit. Your picture of label is very hard to read model number. Not clear to me, had to click it to see it better. So you have a dmr702, here's a link that may help you along:
https://www.arprv.com/rm3762-dmr702.php
Hope it helps. Good luck. If need any help in hespria, just let me know.

[george6robles]

https://www.arprv.com/rm3762-dmr702.php
Link hopefully helps.

Change of temp is done via buttons.

Set to higher number for colder temps.
If it's over 100°F should still be able to get freezing temperatures in the refrigerator compartment.

Changed thermostat/thermistor will not change anything then likely to decrease performance. If the sensor is set to a temp, and that temp is what says turn on or off. If temp is reading fin when designed for the middle of fridge, you moving it to the fin, it will never turn on unit long enough to cool down the fridge compartment. I bet if you placed your "new" sensor you have in bottom of fridge, would likely get same result.
This case , I would return to original position and sensor.

Then change temp setting. Then check again.

New designs don't always work out. Sometimes. Just wanted to say that. Fan may decrease performance. This unit relys on warmest temp to rise and activate temp sensor. Convection. A fan may or may not change the way it performs.

[rockfordroo]

Originally Posted by rockfordroo

There are ventilation and vent area requirements in the attached document.

UPDATE: Just checked and saw you had a DM702. You should have gotten a similar document with your rig.

I found the DMR702 owners manual, if you don't have it.

[owlandfox]

7/23: 1900.

I have added in some items in hope that the fridge at least gets to 40 degrees.

1. Added aluminized foam in fridge area to soak up air space (less space for hot air to hide)
2. Added aluminized baffle to top of back fridge area to divert hot air out to the vent (remember baffle is still in place)
3. Added two 120 MM computer fans (picture forthcoming). I cut retangular holes in the baffle, mounted them under the fin area and have them blowing up through the fins. These are on constantly. I do not have them switched (I will later on this week) and I'll also put in a 1 amp fuse.
4. Changed thermistor. I have the thermistor on the highest part of the fin and have the buttom to coldest
5. It's on electricity in the driveway.

I started all this at about 6 pm today, temp to start was 69 and at 7:12 pm it is 66. So something seems to be working.

[chaps2018]

My dometic (setting #5) cooled to 34deg overnight and was upper 30's in the evening (by display and 2nd thermometer at bottom of fridge) this past weekend when temps were over 100deg. Although I won't claim success until the cooling is consistent each day and my unit is facing the evening sun.

My thermistor clip is set at midway Top/bottom of internal fin as per my Dometic 3962 instructions.

On the backside of the fridge, I used Reflectix to make a smooth surface for the air to travel from the bottom of the cavity up past the back of the fridge cooling fins and out the vent. I used Metalized tape (duct section at HD or Lowes) to attach the reflectix to the back of fridge, side walls and upper ceiling where the vent is mounted. My objective was to eliminate any dead space for the air to stall and keep the hot air from going into the attic space over the fridge.

I have this squirrel cage fan that will mount to the upper vent cover with the fan exit blowing directly out the upper vent. My objective here is to get the hot air out of the upper cavity behind the fridge. I also purchased the computer-type fans to help exhaust the hot air but they seem to much more inefficient since a large part of the air flow is blocked by the external fridge vent panel. The squirrel cage fan blows 100% out the existing vent.

Finally, i use this temperature controller to control fan operation. I run the power wires down the back of the fridge to the 12v connection behind the bottom vent.

I have dry mounted the fan (will screw into the vent cover) and wired the controller, fuse, etc but have not installed it yet. (DW had other plans those two mornings...).

These ideas are from all the other posts I have read on this subject so thanks to all of you who have furthered this discussion.

I will report back after installation and operational details.

(Side note: Previous rig had a roof vented Norcold and it was rock solid at setting 3 nearly all year long (owned for 7 yrs camped 4 seasons). Only occasionally did I have to set it to 4....of course I was using an analog thermometer not a digital readout like the Dometic...ignorance is bliss? LOL)

[chaps2018]

Originally Posted by owlandfox

...
3. Added two 120 MM computer fans (picture forthcoming). I cut retangular holes in the baffle, mounted them under the fin area and have them blowing up through the fins....

Brilliant mounting scheme. Can't wait to hear your outcome.

[fugawi_tribe]

So I was having issues with my fridge getting cold also. I didn’t know what the thermister was until I called my dealer and he explained to me what I should check. After figuring out what it was I realized it had never been attached to the temperature control slider or whatever it’s called. It was merely leaning against the side wall of the fridge about halfway down or less. I pulled the wire slack so it would reach the top of the fins, attached it to the slider that it should have been attached to in the first place, slid it up as high as it would go and turned it on. This was yesterday afternoon. I checked it this morning and the fridge was at a crisp 28 degrees. Now it might get too cold lol. If anyone needs help let me know, it was really really easy. Once you know what to look for.

[rockfordroo]

There's a pic of the thermistor in Post #12.

[fugawi_tribe]

Originally Posted by rockfordroo

There's a pic of the thermistor in Post #12.

Yes that’s the slider thing I was referring to but the wire that attaches to it is not in the picture. That is the part I needed to see in order to resolve my issue. I had no idea the two were supposed to be connected.

[rockfordroo]

Originally Posted by fugawi_tribe

Yes that’s the slider thing I was referring to but the wire that attaches to it is not in the picture. That is the part I needed to see in order to resolve my issue. I had no idea the two were supposed to be connected.

The thermistor is up inside the plastic slider. You can see the wire for it under the bottom of the fins.

[KBR1948]

Hello, this is my first post to this forum. I have a few questions for those that seem to know a whole lot more about my Dometic fridge than I do. I usually start the fridge up a couple of days before loading it for a trip. The fridge and freezer both get cold while running on my house current. Just before leaving, I hook the Roo up to my vehicle, unplug the trailer, and bring in the slides. Although the fridge was working fine, I get an error message which, according to my manual, means that the DC voltage is out of range which is 8 to 18 volts. The controls indicate that there are three modes, AU, LP and DC. I was expecting the fridge to run on DC while traveling but that does not seem to be the case. The Dometic manual lists only two modes, AU & LP. When I connect the Roo to my truck, I can here the igniter clicking so I know its looking for LP. My first question is, does the Dometic DMR702 run on DC current? I notice that one contributor runs the fridge on LP while traveling. My second question is - Is that a safe thing to do? This is my third trailer and I've always turned off the LP for travel. Once we get set up at a site, I can re-start the fridge using the electrical hoop-up. Any comments will be welcome and useful. Thanks.

[bikendan]

KBR, I don't know of any Roo with a 3-way fridge. They all have 2-way fridges, LP and 110vAC.
The majority of RVers run their 2-way fridges on LP while traveling, including me.

[jking46]

It's perfectly safe to run your fridge on propane while traveling.
For me, it's all about the length of the trip. Less than 2 hours I don't turn it on. Everything will still be plenty cold when you arrive. Over 2 hours, I use propane.