Freezer works, fridge does not.

[Scovndrel]

Hello!

I have a 2017 Travel Lite 625SL truck camper that I bought new.
The fridge/freezer unit which is a Dometic RM2354, mfg 2016, worked OK when I bought it, but never as well as the larger units in two other rigs I've owned. It got intermittent for a while, and now it is consistently bad.

I have a digital thermometer with an external probe that I jammed into the fridge through the thermistor hole, so I can check the temp without opening the door. It agrees within a few degrees with the analog one that is inside the fridge.

The problem is that while the freezer can freeze things and keep them frozen, the refrigerator portion does not get very cold, depending on the outside temp. For example, this morning we got a little frost on the roof of our house, and the RV fridge was at 35 degrees. On warmer days (65 to 75 degrees), the fridge gets to about 55 or 65 degrees, only a few degrees below the ambient air temp outside. But the ice packs in the freezer are still frozen solid. The cold just is not making its way into the fridge section well.

I am testing in my driveway. The fridge is perfectly level according to the bullseye level inside the fridge.

I have moved the thermistor clip to different areas on the fins, though my understanding is that this is a maximum of 5 degrees variance, not enough to cover what I am seeing.
The thermistor, when dunked in a glass of cold water with crushed ice, reads 9370 Ohms - right in "the zone". After reading a bit, I have now left the thermistor unplugged and we'll see what happens - it has been about an hour since I unplugged it.

There has never been an ammonia smell nor any yellow residue.

I have very little stuff in the fridge, so there is no air circulation blockage.

I have a little solar fan blowing on the condensor. It doesn't seem to make any difference. I have tried a battery powered fan inside the fridge. No difference.

It doesn't seem to matter whether it's on shore power or propane; in either case the chimney gets hot, the freezer stays frozen, and the fridge is tepid.

I have inspected the door seal. It is tight all the way around.

While I did not measure clearances exactly, I looked at the diagrams in the manual, and the fridge compartment looks pretty much the same as every RV fridge compartment I have looked at.

So, anyone have ideas what the heck is going on?
How, exactly, is the cold supposed to enter the main refrigerator compartment? Does it trickle down from the freezer, or is it a separate mechanism, attached to the cooling unit independently from the freezer?

[Scovndrel]

I never said anything about working on one type of energy but not another.
Why does your post contain a link to a review of full size home refrigerators?

[Annalee]

If your fridge works on gas but it does not work on 110v AC then there is something wrong with your electrical power supply. First, check that you are getting the energy to your refrigerator. Check your circuit breakers and fuses. If all seems well there then you will want to test the outlet your fridge is being plugged into. Using a multimeter is the best option, you are looking for a reading between 110 and 120 volts, but if a multimeter isn’t available then you can plug a fan, lamp, or another small device into the plug to test if the appliance is getting energy.
Refrigerators review

[Scovndrel]

As an IT guy who uses Google a lot for troubleshooting, I can't stand it when I find a thread that pretty much exactly matches my issue, and then it just... stops. With no resolution posted.

I learned a lot about RV refrigerators in the last few weeks.

BTW my fridge got down to 4.7 degrees last night. Crazy cold. I've just hooked up the control board again and switched it back to factory wiring.

[Hurricaner]

This was darn good tread, thanks to the op for hanging in there and posting the solution. A lot of the complaints on gas reefers are due to poor installs.

Sam

[Scovndrel]

You’re right of course. The builder, not the dealer. Will edit the post.

[dougrainer]

Don't blame the dealer but the OEM maker. I would blame the dealer if he had been asked to address a no cooling issue. Your problem and resolution goes to show a LOT of RV refer problems go to installation errors by the OEM's. Dometic and Norcold try to Audit installations by the OEM's, but catching things like your problem is not something they could catch. The installers on the production line do not know correct install and what to look for when installing. Doug

[Scovndrel]

P.S. Big shout out to David Force at RV Cooling Unit Warehouse (https://rvcoolingunit.com) for sticking with me on this. Before the sale, David talked me through a bunch of troubleshooting. After the sale, he answered questions I had regarding installing the new cooling unit into the fridge box. When it didn't work right, David answered multiple e-mails trying to solve this during business hours, in the evening, and even on the weekend. I could not have asked for better customer service. He could not have known that the dealer did not block the airspace correctly.

[Scovndrel]

Update and resolution:
While looking through the installation manual very carefully for any clues about why the fridge did not like my cabinet, I came across this text:

"When installing the refrigerator, the installer must block the space between the storage cabinet and the top of the refrigerator, otherwise heat will become trapped in this space, making the top of the refrigerator hot, thus reducing the efficiency of the unit."

My fridge is about 4" shorter than the cabinet it is in, and there is just open air above it. It has never been blocked off properly. There is a little 2" high cardboard barrier running across the top rear of the fridge that says "This is not packaging, do not remove this." but it doesn't say why. Now I know that it was supposed to help block the air space on the top of the fridge. But being only 2" high, it was NOT blocking that air space.

When I relayed this to David, he confirmed that this could very well be my issue, and also sent me a diagram showing that, if possible, I should try and block the airspace between the back of the fridge behind the condenser fins and the cabinet wall as well, leaving only about 1/2" of space so the air has to run up through the fins to escape out the top.

So I went to Home Depot and got some 3/4" thick styrofoam insulation and spray adhesive. I cut the styrofoam into correctly sized pieces and stacked them until the stack was JUST thick enough, stuck them together into one big block, wrapped it in aluminum foil for protection from heat, and attached it to the cabinet wall behind where the fins would go.

For the air space above the fridge, I removed the useless cardboard barrier, and cut a piece of cushion foam to the appropriate size. I stuffed that in from the front after sliding the fridge into the cabinet, and used a piece of PVC pipe to push the foam to the back. Then I climbed up a ladder, removed the roof vent cap, cut the wire mesh, reached down in there and adjusted the foam so it's completely blocking the air space on top of the fridge, but not touching the fins or tube. Then fixed the wire mesh and put the roof vent cap back on.

I then hooked the heater up to direct 120V again and reconnected my thermometer with remote probe that goes inside the fridge so I can check the temp without opening the door.

Just 4 hours after I put it back together, the fridge was at 15 degrees. I didn’t believe it at first, I figured my thermometer must be freaking out so I put the metal-spring-type fridge thermometer and a bottle of water in there. I went back out 15 minutes later and the second thermometer confirmed 15 degrees and the water bottle was already getting chilly. There is frost on the evap fins for the first time EVER in the life of this fridge, and there was a bit of ice on the drip trays.

The freezer thermometer is reading -20 degrees. That's as low as that thermometer goes. All of the mercury is down inside the bulb.

So I think we can call this fixed, and the problem was hot air being trapped in the dead space above the fridge. Kinda makes me wonder whether my original cooling unit was in fact blocked, but that’s water under the bridge at this point. Even if it wasn’t blocked, maybe it was a skinny ammonia charge, no way to know now.

So there you go. There's something to add to the troubleshooting questions: Is the open air space in the cabinet on top of the fridge properly blocked off, or is hot air pooling up there, working against the cooling unit? The builder (Travel Lite) never installed the fridge properly. It has never worked really well, even when it was brand new.

I look forward to some really freaking cold food and drinks now.

Next up: Returning the wiring to the default config, with thermistor connected and control board regulating the boiler, and making sure it STILL works right.

[Scovndrel]

Update: Ran one more test recommended by David at rvcoolingunit.com; I pulled the fridge out of the cabinet and set it on the floor of the camper.

20 hours later, the freezer is at zero, and the fridge is at 26 degrees.

So it seems that the fridge does not like the cabinet. The unit worked when it was new, and the only thing I’ve changed in that cabinet is running a pair of wires from the solar panels down through there, and adding an air deflector that David recommended to make sure that rising air goes through the condensor fins. Maybe that is restricting air flow too much? Even with two fans blowing air through there? I can’t leave the vent cap off.

[Dave_H_M]

What Doug said.

[Scovndrel]

Fridge still not holding below about 34 degrees during the day, and freezer went up to 15 during the day. Infrared thermometer says the pipe in the middle of the chimney is more than 230 degrees (it maxes out) so it's cooking the ammonia just fine.

David at rvcoolingunit.com, who I bought the repair through, said a 3/8" bead of thermal mastic should be plenty. He wanted me to work on the airflow through the condensor fins so I'm doing that tonight. But most likely I'll be calling Larry at Pines in the morning to go through it all.

[Scovndrel]

I put about 3/8" bead of thermal mastic all along the cooling tubes and kinda poked it against the tube so it would stick there a little better. I used about 40% of the mastic cylinder on about 3 feet of tubing. Knew I should have taken a photo of how much I used.

I suppose I could remove it from the cabinet again and reinstall with a fresh tube of the stuff and put two huge beads next to each other completely covering the tubes.

I used some of the can of Great Stuff Window & Door that they included, put about a 1/2" bead (which began expanding right away) of foam around the fridge cavity before setting the cooling unit in place and adding the metal tape around the edges.

I'll check again after it's been wired direct for 24 hours. That will be about 10am PST tomorrow.

[dougrainer]

The freezer if NOT below 10 degrees wired direct to 120 for 24 hours---------------------------BAD COOLING UNIT. Regardless of it being repaired. It was either not repaired correctly(Blockage tube removed and new one welded in place), or not charged correctly. There is no difference between the size of an RV refer and the capacity for cooling as long as operational items are correct. Doug

OR the cooling unit was not reinstalled correctly with adequate Thermal Mastic and the CU sealed to the box correctly. One item that will cause replacement problems in untrained hands is lack of enough Thermal Mastic. You CANNOT use too much Thermal Mastic when installing a cooling unit. Thermal Mastic is what promotes the removal of Heat.

[Scovndrel]

Update: Cooling unit was sent off to Pines and repaired. Have reinstalled.
The freezer got to 25 degrees in 3 hours, then kind of leveled off there for 24 hours. Fridge stayed a few degrees above ambient temp. But then after 36 hours, freezer got to 15 degrees and fridge got to 30. This was in the morning after a cold night. All this was with the thermistor still hooked up.

This morning after taking that reading, I turned off the control panel and hooked the 120V element directly to power source. Fridge is back up to 35 degrees right now, freezer still at about 15.

I have a thermometer with a probe that I've run through the thermistor wire hole, lets me check fridge temp without opening it. Still have to open it to check freezer.

I've heard it said that my smaller unit (RM2354 for compact truck camper) is not as good at cooling as larger units. Can anyone tell me with some certainty what temps my unit should be able to achieve with ambient temps around 45-50 degrees outside, and what it should be able to do in the summer with an assist from a solar fan in the back of the cabinet aimed at the condensor fins?

I'm not sure I'll ever trust this fridge with perishable food for more than a day or so again. It might be an expensive drink cooler now.