Dometic RM1350 not cooling, tried just about everything

[BigDaveZJ]

Last summer the RM1350 in our 2019 260RD stopped cooling on LP while we were boondocking. Would cool on AC just fine but that has mostly stopped. Ran through a litany of diagnostics and checking different parts. Fans come on, AC heating elements work, LP pressure is tested and within spec, igniter works, thermocouple works, no errors on the display or when running the test mode from the upper board, all fuses checked, reset button on the thermocoupler thingie at the bottom of the flue has been checked, gone over everything with a multimeter, cleaned the flue, new LP burner, swapped lower boards for the heck of it, burped the cooling unit, no major changes. After burping the cooling unit, it cooled again on AC. But since all we really do is boondock, LP operation is more important so I switched it to LP and lost cooling in both modes. I admittedly did not burp it as most people I've seen online suggest, I just flipped it upside down, rocked it back and forth a couple times before flipping it back over and put it back in. I definitely heard the chemicals sloshing around, and there are zero signs of any chemical leaks from the cooling unit. I have noticed that the back wall of the freezer and the cooling fins are occasionally 15-20* over ambient on AC and LP so I believe it is heating the cooling unit as it should. The fans still kick on as well.

At this point, the only thing I can figure is the chemicals in the cooling unit have crystalized somewhere and are preventing everything from flowing as it should. I'm leaning towards the burping "trick" again, but leave it upside down overnight to give the chemicals a chance to do their thing. I'd really rather not throw a new cooling unit at it if I can avoid it, especially since the one in there has worked on occasion.

Anything anyone can think of that I'm missing?

 

[Second Chance]

I originally posted this a couple of years back after problems with our Norcold 1210. A very good tech taught be about the absorption refrigerator "reboot." Perhaps there's something in here of use:

Our absorption fridge quit cooling last winter (had been in one site without moving for a couple of months). I called our trusted RV tech for advice... I posted the following after that experience:

RV techs call it a "refrigerator reboot."

When your absorption fridge quits cooling (cooling unit less than two years old) and an experienced RV technician tells you to do a "fridge reboot," listen to him/her. Late last week and over the weekend our Norcold 1210 fridge started not maintaining proper temperatures. I tracked it with a fridge/freezer thermometer and my infrared thermometer and got an ever-tightening knot in my gut. First thing Monday morning I contacted our favorite technician here in Las Cruces, NM, Richard's RV Service, fearing the worst. He asked the following questions:
Is it the same on AC and propane? Answer: Yes.
Did the problem come on suddenly - like flipping a switch? Answer: No.
Did you smell ammonia? Answer: No.
Do you see any yellow residue around the boiler, coils, or any of the other tubing on the cooling unit? Answer: No.
Do you hear the cooling fans in the back cycling on and off? Answer: I haven't noticed them like I usually do - but the weather has been cooler.

Richard's instructions: Turn the fridge off for at least five hours and let everything get down to ambient temperature in the back. Using a rubber mallet, periodically tap on all the pipes, tubes, and other refrigerant conduits I can reach, both while it's cooling down and after it's completely cooled. This process took until about 2:00 Monday afternoon. I then turned the fridge back on and continued to do the "rubber mallet frappage" periodically while the fridge was warming up/cooling down. I turned the fridge back on mid-afternoon and by the time we went to bed Monday evening, both the fridge and the freezer were getting back down in normal ranges and the infrared readings on the fridge fins and the back walls of the freezer compartments were very good.

I kept a log and updated Richard a couple of times on Tuesday and he dropped by yesterday (Wednesday) to check. His diagnosis... an air bubble or chemical membrane in the refrigerant system. He said, "Congratulations!" and pronounced the fridge healthy. We both think the issue occurred because our RV hasn't been moved since we pulled onto this site on 10 November and the jostling an absorption refrigerator gets bouncing down the road helps keep the refrigerant stirred up and moving.

Rob

 

[BigDaveZJ]

Good info. Mine gets plenty of jostling (8.5 miles of dirt roads after 75+ miles of curvy dirt roads to get to our boondock spot), but at this point I don't think the cooling unit has actually failed, it just needs a reboot as you put it. I'll the tapping technique to my burping procedure and hope for the best!

 

[BigDaveZJ]

So yesterday I pulled the new lower board out and put the old back in so I can return the board. Did nothing other than swap boards, and the fridge is at 34* this morning.

 

[Second Chance]

So yesterday I pulled the new lower board out and put the old back in so I can return the board. Did nothing other than swap boards, and the fridge is at 34* this morning.

Perhaps a cleaner/better connection than previously?

Rob

 

[BigDaveZJ]

At this point I think I'm going to use this thread as a journal of sorts to track what's been going on.

Holding temp on AC. Today we had some blips in power from Xcel, and somehow a GFCI tripped on the shop where the camper is plugged in to. It switched to LP around 1:15 based on when my Nest camera went offline. At 5:15 the freezer was at 28* and the fridge at 56* with an ambient around 60*. Got it back on AC now, so we'll see where it's at tomorrow I guess.

 

[Second Chance]

At this point I think I'm going to use this thread as a journal of sorts to track what's been going on.

Holding temp on AC. Today we had some blips in power from Xcel, and somehow a GFCI tripped on the shop where the camper is plugged in to. It switched to LP around 1:15 based on when my Nest camera went offline. At 5:15 the freezer was at 28* and the fridge at 56* with an ambient around 60*. Got it back on AC now, so we'll see where it's at tomorrow I guess.

Absorption fridges usually perform better on LP than on AC, so this still doesn't sound right (assuming that it still had good 12VDC power for the control board and gas valve).

Rob

 

[BigDaveZJ]

Yup, 12V is good, and LP pressure has been tested within spec. I'm stumped. In the service manual there is mention of the flue becoming detached from the cooling unit in rare instances with "rough riding coaches." We've checked this as well, and it appears to be intact.

 

[AmeliaKD]

I started having the same issue yesterday with my Norcold (now Norwarm) in 2021 260RD. We can't get the fridge to cool down. Outdoor temp is 70 degrees.

We move every 4 or 5 days. Yesterday morning as we hit the road to our next location, I noticed temp in the fridge rising slowly. I have a SensorPush remote thermometer in it and it alerted me to the rise in temp. We have a set of lithium batteries (and solar) so we can keep the fridge running while driving. We checked and the fridge was running on AC from the batteries. The temp continued to rise slowly all day.

We got to our next location on 50 amp, still not cooling. Cut over to LP, not cooling. Turned off for 5 minutes, back on, nada. I noticed some water in the bottom and side of the interior fridge which made me check the drip tray (probably splashed out while driving some windy back roads). It had a lot of water in it (and oddly, an ice cube but not one made from the freezer ice tray, but similar in size). I checked the outdoor panel and saw no water in the catch tray. I unplugged the white tube and lots of water came flowing out. I did find a piece of something/trash inside in the condensation drip tray that may have been plugging the outflow. Checked this morning and the condensation tray is empty, so that part is fixed, I hope. And humidity has dropped from 90% to 50%.

It has been working great on a temp setting of 4 until now. We tried increasing it to 7 then to 9, no colder.

Read in the manual that if the temperature sensor should fail, it will cut over to a backup operation system to cool it. We unplug the sensor, but that didn't help.

Checked this morning and it is hovering at 48 degrees since midnight (lots of cold beer in the fridge might be helping). Freezers seem ok, frozen bananas are soft but everything else is frozen.

I'm going to run through the suggested steps of turning off the fridge as @secondchance suggested, if we can get some ice to put in the fridge to keep it cold for the 5 hours.

Any other ideas?

Karen

 

[AmeliaKD]

We called our dealership in MD and they suggested that something was clogged/frozen/not-moving in the pipes, and, as Rob [MENTION=870]Second Chance[/MENTION] posted, to do the rubber mallet tapping on the black horizontal cylinder thingy inside the lower panel (I forget what he called it - recovery tank?). He didn't say to do the 5 hour wait period (it had already been off for an hour though), just tap the tank and the pipes going in and out of it. We did that but it didn't fix it - the pipes got very hot so that piece was working, but the fans weren't coming on.

He thought maybe the thermal sensor disk that turns the fans on and off wasn't working. He had us remove the wires connecting to the sensor (attached to the right side of the fins behind the upper panel) and connect them using a 10 or 15 amp fuse. We had a 10 amp handy, so used that. The fans turned on and the fridge and freezer started cooling, slowly. The fans are running continuously now and the fridge and freezer are holding good temps (it took over 24 hours for it to get into reasonable temps). The fridge is staying within the 32-38 degree range. The freezer seems to hold between 5 and 9 degrees - not getting down to 0 to -10, but ok.

Hoping it will work for the remaining 8 days of our trip, then we'll get it into the shop to be looked at.

 

[BigDaveZJ]

The switch for the fans is a common failure point, also one that's generally easy to test and bypass. The fans on mine are for sure working.

After switching mine back to AC the other day, it cooled back down just fine and held for a few days. Switched to LP and nothing. Back to AC . . . . nothing.

 

[BigDaveZJ]

Works fine on AC now, freezer holding temp on LP, but the fridge is at ambient.

 

[BigDaveZJ]

Works fine on AC now, freezer holding temp on LP, but the fridge is at ambient.

After roughly 10+ nights of camping so far this season, it's still consistently working on AC and LP is keeping the freezer around 10*F with very little cooling the fridge. Only real further testing I've done is to disconnect the fridge from the camper LP system and hook it straight to a different LP tank, no change in performance. Also cleaned the orifice again, no change. So at this point it's pretty much narrowed down to either the LP valve on the fridge, or the flue has begun to separate from the cooling unit and causing subpar cooling. There's some tests I can run on the lower board too I guess, but I swapped that and nothing changed so I'm assuming it's fine.

 

[napsterg]

I admittedly did not burp it as most people I've seen online suggest, I just flipped it upside down, rocked it back and forth a couple times before flipping it back over and put it back in.
I'm leaning towards the burping "trick" again, but leave it upside down overnight to give the chemicals a chance to do their thing.

Did you ever solve your fridge problem? I have a lot of the same issues. Everything seems to be working but no cooling of fridge or freezer. No error messages, no yellow residue, AC heating element heats up, LP fires up, ziggy tubing above flue/heater going up the side gets very hot, above 100 Celcius at the top, with temperature dropping into 20s Celcius in the cooling fin at top, cooling fans start and shutoff after a few minutes (with propane anyway).

I haven't checked the control board per say but fuses are good and like I said everything electric seems to be working. I tried the rubber mallet reboot of Second Chance with no change. I have not done the "burping" as you described above or thought of doing (24 hours upside down) but how did you manage this? The fridge is supposedly over 200 pounds? I guess with your handle of "BigDave" you could manage this but this weight is out of my 66 year old league and the confines of my trailer won't help. Maybe with the help of my spry 61 year old rving neighbour?

 

[Mrdieseldoctr]

If you are seeing a drop that significant in the upper tubes, you have a blockage up there. I just fought this same issue and it finally dawned on me when we picked our rig up,the kind folks had it plugged in and fridge on in a very sloped driveway….. it burnt our cooling unit up and I replaced it. Fire it up and start feeling your way down the tubes, you will be able to pinpoint the blockage, or if you can find a flir gun you can see it.

 

[napsterg]

If you are seeing a drop that significant in the upper tubes, you have a blockage up there. I just fought this same issue and it finally dawned on me when we picked our rig up,the kind folks had it plugged in and fridge on in a very sloped driveway….. it burnt our cooling unit up and I replaced it. Fire it up and start feeling your way down the tubes, you will be able to pinpoint the blockage, or if you can find a flir gun you can see it.

Ended up "burping" it, as a blockage, as you identify, seemed like the likely culprit and really my last resort. I had to pull the trailer out of my tight, beside the house, storage spot onto the lawn so I could extend both fridge and dinette slides so we could pull the fridge out, wriggling it by the island, pull it forward and flip it on it's side between the dinette and island and then on it's head in the living room area. A little bit of gurgling but when we flipped it back over, after 24 hours, it sounded like Niagara falls with all the liquid running through the pipes. I levelled it out where it sat in the middle of trailer, let it sit overnight and plugged it in the next day. Nothing worked until I figured out I had to connect the 12V to run the "brain" of the fridge. Anyway, first the freezer cooled down and then slowly the fridge compartment. On the coldest fridge setting I was getting freezer wall readings of -22 C and the fridge fins of -2C. Fridge LED reading was down to 34 F so I turned it down to my usual setting of 2 out of 5 and it levelled out to 37F.
Shut it off, letting it settle to ambient temp and wrangled it back into it's spot in the slide with the help of a couple of guys. Buttoned up the electrical and propane connections moved the trailer back into it's level parking spot. Let it sit overnight, started it on AC again and watched it slowly cool down to 37F. Shut it off for a bit then started it on propane and it cooled down nicely. Talked about relief. I hope it lasts but from others experience sometimes it goes bad again.

As you point out, what I think caused the problem, was on our last camping trip I pull the trailer out of it's spot onto the sloped yard and did some loading while waiting for my wife, who was a bit late coming from an errand. All the time running the fridge on propane. This hour at the slope it was likely caused the blockage. I'm definitely going to be more cognizant of slope in the future as I don't want to have to pay $5000 for a new fridge or maybe less for some of the alternatives but still a pain in the butt never mind supply and delivery issues.

 

[Hoopy Frood]

From what I've read, not personal experience, the blockage can be incremental. It may not happened all at one time but gradually developed a block. All those times of sitting and running while out of level could have contributed to the issue over time. Like I said, this is not personal experience, just what I've read.

 

[Mrdieseldoctr]

From what I've read, not personal experience, the blockage can be incremental. It may not happened all at one time but gradually developed a block. All those times of sitting and running while out of level could have contributed to the issue over time. Like I said, this is not personal experience, just what I've read.

That’s true, once the water in the unit boils it crystallizes the rust inhibitor and that causes the blockage. Once those crystals form they never dissipate, that’s why burping sometimes works and sometimes it doesn’t. If I can dig it out of the scrap bin I will post pics of ours, I cut it apart and it was shocking how plugged it was.

 

[BigDaveZJ]

Never fully figured my issue out. Camper has been plugged in to AC since the summer and fridge is working just fine. Haven't gotten around to trying it on LP for quite a while.

I could probably burp the fridge myself if needed (as the handle implies lol) but my wife was there to help, mainly to make sure I didn't hurt the fridge, camper, or myself!