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Old 06-18-2010, 10:44 PM   #1
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Dometic RM1350 and GT378

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
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Old 06-18-2010, 10:57 PM   #2
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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.
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Old 06-18-2010, 11:09 PM   #3
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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.
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Old 06-19-2010, 12:04 AM   #4
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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?
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Old 06-19-2010, 12:14 AM   #5
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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.
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Old 06-19-2010, 12:23 AM   #6
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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.
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Old 06-19-2010, 12:32 AM   #7
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Very nice and clean job Jeeper! Nothing like taking care of the problem yourself.
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Old 06-19-2010, 05:44 AM   #8
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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
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Old 06-19-2010, 11:41 AM   #9
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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.
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Nights camped in 2009: 53 | Nights camped in 2010: 55
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Old 06-19-2010, 09:05 PM   #10
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Quote:
Originally Posted by bad1032 View Post
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)
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Nights camped in 2009: 53 | Nights camped in 2010: 55
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