Dometic RM1350 and GT378

[NWJeeper]

From day one I kinda figured that the Dometic RM1350 4-door fridge in our Georgetown 378 didn't work as well as other refrigerators we had in other rigs. When outside temperatures started to climb the refrigerator would have a hard time keeping below 40 degrees and would sometimes climb to around 44 before it could catch up and cool back down. I just figured it was size of the unit and the high outside temperatures. Now after 2 years it intermittently stopped cooling all together especially on propane. We ended up taking a scheduled 10 day trip using coolers and ice because we couldn't trust it. Once home we took it to a local Dometic authorized repair shop. They ran tests and talked with Dometic and were told to replace the thermistor. The shop called and said it was working and to pick up the rig. It cooled just fine over night on AC but the next morning I drove the rig into town to put gas in it and then parked it in the driveway while I washed it. The whole time the refrigerator was running on propane and once again it failed and started warming up. It was partially sunny out and the ambient air temperatures were around 74 degrees. Once again we took it back to the shop. They watched it for a whole week and it worked flawlessly on both AC and propane. Through inspection and talking with Dometic the repair technician identified a deficiency in venting which would cause the fridge to run poorly.

It would appear that Forest River has installed the vents on the roof too far forward. Maybe it's because there is a structural aluminum beam in the way of where the vent should go. Because of this the air rising from the gas flue ends up in a dead head area in the cabinet rather than exiting via the vent. The problem is made worse by the fact that FR did not block off the dead air space above the fridge which from what I can gather is a must for all RV refrigerator installs.

Dometic's suggestion to the repair tech was to install metal baffling so as to help the flow of hot air towards the vent. They also admitted they have had to run as many as 5 fans behind them to get them to work right (probably in RVs where the refrigerator is installed in a slide and doesn't have a roof vent).

Dometic was willing to pay for problems with the fridge but not the poor installation which is out of their control. I don't blame them. An email and 2 phone calls to FR were never returned so instead of waiting for my Dometic warranty to run out I decided to tackle the job of improving the venting myself. If I don't eliminate those issues then we can't move on to determine if there really is a problem with the fridge.

Modifications in Post #2

[NWJeeper]

We removed the fridge using a transmission jack and moved it out of the way. Using sheet metal I rolled two pieces to help transition the rising air towards the vent. Once installed it was smoothed out using aluminum speed tape.

Metal corner piece installed to the rear of the vent to move the flue gasses towards the vent:



Metal placed against outside wall and rolling towards the vent:



To help in moving air I purchased two axial fans from WW Grainger. The fans are rated at 107cfm and draw .51 amps per fan and measure a little over 4" square. Price was right around $41 each. Grainger has a large selection of fans available. The fans were zip tied to the underside of the wire mesh in the vent cover.



Because our rig has dark full body paint I also decided another layer of insulation to try and keep the area a little cooler might not hurt. I purchased a roll of sound/heat insulation similar to that used in generator compartments. I used spray on headliner glue (contact cement) to glue it to the wall.



More in the next post.

[NWJeeper]

The issue of the dead air space over the fridge was taken care of by bending a piece of metal to hang down about 1.5" from the ceiling and was installed at the inner edge of the vent running across the entire width of the cabinet. The metal was made to hang about 1/4" higher than the top of the fridge, to that I used aluminum tape to attach a strip of rubber to hang down another 1/2" or so. In this way when the fridge was re-installed the rubber would ride up over the top of the fridge and thereby close off the dead space above the fridge.



Wires for the upper fans were run down the outside wall & left hanging until the fridge was installed. To get them to run with the factory fans I tapped into the fan wires after the thermostat and ran that wire along with all the rest on the fridge behind the cooling unit to the bottom. Once the fridge was installed the positive wires from the fans were connected to the wire tapped into the fridge fans and the negative wire was paired up with the refrigerators negative supply lead.

We fired it back up on propane and will be watching it in our garage. Hopefully we will see some warmer temperatures and we can get a good idea of whether the fridge will cool correctly. If not it will be back down to the Dometic shop with pictures in hand of the modifications made so far.

From the research I have found though we (Forest River owners) aren't the only ones having troubles with these fridges. I have read where some are on their 2nd fridge and it too is acting up. It would appear that there may be more wrong with these units than Dometic is willing to fess up to at the moment.

Also, it was also related to our technician that because of poor cooling issues with these refrigerators, Dometic changed the installation and venting requirements sometime in 2010. So, even if installed to thier specifications when your rig was built they may still not honor the warranty if it isn't installed to 2010 standards, a circumstance I find to be totally crappy on Dometics part.

[red.jimbo]

Not only was your mod well done, but the post is magnificent. Bravo.

How much do you figure the additional cooling fans will impact your battery drain when dry camping? About how much do the fans run in a typical day? I'm tempted to add them.

What is the black wire coming through the roof vent? Video coax? Solar Power?

[NWJeeper]

The extra fans draw 1 amp together. About the same as the factory fans so all totaled 2 amps. Typically the fans will run more the hotter it is outside and the longer the flame has to run to keep the fridge cool. If running on AC then they usually do not run much. One tip though on the fans don't drop them! I dropped one during the install and it is making a bad noise. $41 down the drain. I will have to pull the vent on the roof to remove it as the only other way to get at them is to pull the fridge. I went with high CFM fans and perhaps one could do with less as they are a bit noisier than I had expected. I will just disable the bad one for now and see how it does with the one.

The other wire you mentioned is from my solar panels.

[NWJeeper]

A few other interesting things I have learned about the RM1350. The fridge will go into an automatic defrost mode 60 hours after power up and then will continue to do so every 48 hours. For this reason Dometic advises that the fridge be turned on between the hours of 4 and 10PM. If turned on at 4pm the fridge will be defrosting at 4am on the 3rd day and then at 4am every other day. The cycle can be reset by turning off the fridge and turning it back on again. Probably not a bad idea if you are dry camping to keep from using too much battery power is to turn the fridge off and back on every other day to reset the timer.

The water supply line for the ice maker and water dispenser has a heating tube on it that is thermostatically controlled to turn on and keep the line from freezing in cold temperatures. Another power draw when dry camping but how much I don't' know. Probably negligible.

[Willie]

Very nice and clean job Jeeper! Nothing like taking care of the problem yourself.

[bad1032]

The refrigerator should go through a defrost after it runs for 48 hours for 2 hours and then it should start cooling again. We recommend that it is turned on between 12:00 noon and 4 pm so that the defrost runs in the middle of the night (it cools for 36 hours before the initial defrost will occur). I do not recommend replacing the board for the issue you are describing. Has McGeorge's looked at it for you?

This was Dometics response to my questions about the issues

[NWJeeper]

Update:

After installing the fridge and starting it on propane it cooled from 56 degrees to 36 degrees in 4 hours and has held that through the night. Fans came on at least once during that first 4 hours, the airflow with the two 107 CFM fans is enough to pull a sheet of paper against the intake door vent. Going to disable one of the fans I put in due to excessive noise as I had dropped it while installing it which messed it up. I think FR should have figured out a way to use a Fantastic Fan for a vent rather than just the standard cap.

Still hoping for hotter outside air temperatures to really get an idea if the changes will help.

[NWJeeper]

Originally Posted by bad1032

The refrigerator should go through a defrost after it runs for 48 hours for 2 hours and then it should start cooling again. We recommend that it is turned on between 12:00 noon and 4 pm so that the defrost runs in the middle of the night (it cools for 36 hours before the initial defrost will occur). I do not recommend replacing the board for the issue you are describing. Has McGeorge's looked at it for you?

This was Dometics response to my questions about the issues

I was curious about this as the information I had came from another forum so I pulled out the manual for our RM1350 and this is what it says:

AUTOMATIC COOLING UNIT CYCLING SYSTEM AND LOW AMBIENT CONTROL

The refrigerator has been designed with an automatic cooling unit cycling system that helps reduce frost build up in the fresh food compartment. The first automatic frost reduction cooling unit cycle begins 60 hours after turning "on" the refrigerator (for best operational results the refrigerator should be turned on anytime between 4 and 10pm), and will last for approximately 120 minutes. Thereafter, the cycle will automatically repeat every 48 hours as long as the refrigerator continues to run. The automatic Low Ambient Control (LAC ensures trouble free operation in low ambient temperatures (e.g below 50 degrees F)

[bad1032]

Thats the email I got right from Dometic, Me I dont like the fridge getting above 40, I think its a P.O.S and they need to design something better. The other Hotor homes and %th wheels never had an issue. Oh well I hope the mod you did corrects the problem and if so I will be putting some extra fans on mine.

[NWJeeper]

So far 2 days running and the fridge is holding at 36 degrees on propane. I reduced the thermostat setting from 3 to 2 last night as it has been realatively cool for spring around here and the fridge is empty(high temps around 55 most of the time) and it rose to 37 degrees, no problem there. There is a chance of 70 degree weather this next week (I'll believe it when I see it) which means my garage could hit 75 to 80 inside and that will be a better test of how the modifications work. However I really would like to see some direct sunlight on that side of the rig and 80 degree weather to really see what happens. Keping my fingers crossed.

[red.jimbo]

Question:

You mentioned the fan noise. Which position do you think produces the most noise inside your coach? The fans attached to the rear metal panel on the refrigerator, or the ones you attached to the roof vent?

My guess is the ones attached to the back of the unit, but I would like to know your your first hand perspective.

[cfsoistman]

Originally Posted by NWJeeper

So far 2 days running and the fridge is holding at 36 degrees on propane. I reduced the thermostat setting from 3 to 2 last night as it has been realatively cool for spring around here and the fridge is empty(high temps around 55 most of the time) and it rose to 37 degrees, no problem there. There is a chance of 70 degree weather this next week (I'll believe it when I see it) which means my garage could hit 75 to 80 inside and that will be a better test of how the modifications work. However I really would like to see some direct sunlight on that side of the rig and 80 degree weather to really see what happens. Keping my fingers crossed.

I think you still have one problem with your fridge. After all the work you've done there's no cold beer in there. Add at least 12 beers, preferable cold already. Make that add 11 beers, open the other and enjoy. Allow the other beers a hour or two to get acquainted with the fridge then take out one, drink slowly and compare it with the first. This may require repeated testing just to be sure you have accurate information.

Sound like you've solved the problem. Hopefully the weather will cooperate so you can get the sun directly on that side. Charlie

[ronhanson]

I've installed a fan like you did and I think your fridge will run more efficiently with the modifications but you mentioned your fridge would just quit cooling at times. I would think even with poor venting you would still have some cooling and it wouldn't just stop unless there is some mechanism that tries to prevent overheating.

[NWJeeper]

Originally Posted by red.jimbo

Question:

You mentioned the fan noise. Which position do you think produces the most noise inside your coach? The fans attached to the rear metal panel on the refrigerator, or the ones you attached to the roof vent?

My guess is the ones attached to the back of the unit, but I would like to know your your first hand perspective.

Jim, The original fans on the back of the refrigerator don't make that much noise and are hardly noticeable from inside the rig. However in my estimation they are probably about 30CFM fans and are turning at a lower RPM.

The fans I installed on the roof vent are each 107CFM so I am guessing about 3 times more powerful than each factory fan. Add to that the fact I dropped one and made it off balance and it is really noticable inside the rig, louder than the water pump but not as loud as the furnace. I will be disabling the bad one and will see what the noise level is like on the remaining one and report back when I have tested it.

Originally Posted by cfsoistman

I think you still have one problem with your fridge. After all the work you've done there's no cold beer in there. Add at least 12 beers, preferable cold already. Make that add 11 beers, open the other and enjoy. Allow the other beers a hour or two to get acquainted with the fridge then take out one, drink slowly and compare it with the first. This may require repeated testing just to be sure you have accurate information.

Funny you should mention it Charlie as I just had the wife load the fridge up with beers this morning to test it under a "load"

Originally Posted by ronhanson

I've installed a fan like you did and I think your fridge will run more efficiently with the modifications but you mentioned your fridge would just quit cooling at times. I would think even with poor venting you would still have some cooling and it wouldn't just stop unless there is some mechanism that tries to prevent overheating.

Yeah Ron I know, doesn't make sense and I can't rule out an actual problem with the fridge still, like maybe the control board but Dometic was not willing to continue to search for other issues until the venting was taken care of. I still have until September until my 2 year parts & labor portion of the warranty runs out with Dometic so if there is something else wrong I hope it shows itself before then.

[mbtelguy]

According to the Dometic refrigerator manual (see quote below) the refrigerator
will stop for 15 minutes when you shut off your engine. I suspect this could
affect the cooling, especially if your doing a lot of stop/start sight seeing.

However my question is should your refrigerator start-up immediately when
you restart the engine ? anyone know (My MH is in storage)

“Temporary gas lockout:
The gas operation will automatically be locked out for a period
of 15 minutes when the engine is switched off. This will prevent
gas operation e.g. when stopping at a refueling station.”

Also there is a article on refrigerator venting on the following site
which explains some of the issues.

Venting

[NWJeeper]

Mbtelguy, You are correct, it does disable the gas flame when the ignition is turned off so that you don't forget at a gas station when refueling. It was my understanding though that if you force the fridge to run on LP (take it off of "auto" mode) that this will not happen. In really hot climates you might not want it turning off all the time if you are turning the ignition on and off a lot.

Thanks for the link, I will check it out. Their page seems to be having problems loading this morning for some reason. Will try later.

[bad1032]

Well I installed the fans today going to do the tape work later, turned it on so we will see if it fixes the problems, suppose to be near 100 the rest of the week, will let you know the results,

Ok went out today and finished the job, I went and got the pool noodles and aluminum tape and filled the void on top of the fridge, its 98 drgrees and the fridge is hold at 36, I hope this fixed the issue,Thanks jeeper for all your contributions, I know you have help me a few time on issues.

[bad1032]

Ok day 3 with the new fans, its been about 100 degrees here every day, yesterday it went into defrost mode and went to 40, this morning it was back at 35, so I for 1 am glad i added the new fans on top,