Dometic RM1350 cooling fan problem--need wiring/location help

[BobTheBuilder]

I've read all the threads, tech manuals, etc. My rear cooling fans (3) are not working and the fridge was still doing OK until yesterday and there is no significant change in condition, temps etc. Night temps in the low 70s and daytime highs close to 90. Fridge has been dropping to 34 every night and climbing 10-15 degrees by the afternoon. This morning it was 47 at 6 AM and by noon had risen to 51 (yes, the doors are sealed and were last night).
The owners manual diagram identifies the round object in my photo with two black wires as the thermostat. My wiring diagram shows two thermostats with a red wire coming to both of them. I am guessing the thermostat in the photo is not the one for the fans and that it may be more difficult to access but with the wire coloring misidentified, I really don't know. Any passed on knowledge is appreciated! I want to just hot wire the fans to test them and get the air moving but I am not sure which wires or where to make such a bypass of the correct thermostat.

 

[cookie]

The thermostat that you want is located on the cooling fins.
Do not use the one in the picture to hot wire the fans.

Peace
Dave

 

[boatto5er]

Wish I could help. Put fans inside and out of our 1350, installed a curved baffle at top of fridge, added insulation, checked seals and doors. Nothing helped. Ripped it out and installed a Samsung residential fridge.


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[cookie]

Ripped it out and installed a Samsung residential fridge.


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Gus that's exactly what I will do if mine ever fails.
I think I have the only one that works properly. Never had an issue.
Oops, I may have just jinxed myself.

Peace
Dave

 

[BobTheBuilder]

Dave,

will those be the fins at the very top?

 

[cookie]

Yes, and here is a pic of a baffle thatI installed.

Peace
Dave

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[BobTheBuilder]

I disconnected the thermostat and connected the wires--nothing. I found two fuses on the circuit board and both are OK. The fans are very dirty but spin OK. I would not think they would both be bad but tomorrow I'll get them out, clean and test them.

In the meantime fridge is up to 54 and every other day she has hit about 45-47 this time of day, with no fans working.

One other question: I had the sliding thermister on my SOB that attached to the fins. this one is a round probe that is attached to the overhead in the food compartment. Is this a design change from the early units?

 

[wdk450]

Yes, and here is a pic of a baffle thatI installed.

Peace
Dave

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My thought is that it might assure venting airflow across the condenser fins if the baffle sat against the rear of the fins and went up to the top edges of the fins.

2nd big thought that I have had for a long time is that if venting air flow across the cooling unit rear components is so critical, why don't the RV refrigerator manufacturers put a sheet metal pan over the entire back of the cooling unit heat exchange structures to minimize bypass air flow????

- - - Updated - - -

I disconnected the thermostat and connected the wires--nothing. I found two fuses on the circuit board and both are OK. The fans are very dirty but spin OK. I would not think they would both be bad but tomorrow I'll get them out, clean and test them.

In the meantime fridge is up to 54 and every other day she has hit about 45-47 this time of day, with no fans working.

One other question: I had the sliding thermister on my SOB that attached to the fins. this one is a round probe that is attached to the overhead in the food compartment. Is this a design change from the early units?

The fans are 12 volt DC fans. You could test them by directly applying 12 volt DC to the fan wires.

This page has some Dometic add-on cooling fan kits with thermal switches: http://rvcoolingunit.com/-Improve-your-Cooling-Performance-items-C320215.aspx?sid=298

 

[BobTheBuilder]

Re: Dometic RM1350 cooling fan problem----MYSTERY SOLVED, MAYBE, AUTOMATIC COOLING UNIT CYCLE RELATED?

I started this thread because my cooling fans were not operating. However, the fridge had been working OK for the past month (2011 Bighorn that is new to us) with no fans, modest straight baffle near the top and supplementary foam insulation sealing the sides. Outside temps were in the low 90s during the day, no frost build up inside the unit and careful monitoring of the door latches being secured. Morning temps for the fridge were 34 and mid 40s by late afternoon.

2 days ago we got up and temp read 47 at 6 AM and by noon it was 51 eventually climbing to 57! In addition to trying to get my fans working (as described above) I was rereading old forum entries AND the Owners Manual. Under operation I had previously read the section called AUTOMATIC COOLING UNIT CYCLING SYSTEM AND LOW AMBIENT CONTROL where they tell you to start the unit between 4 PM and 10 PM and how it will cycle every 48 hours to ensure trouble free operation in low ambient temperatures (below 50). Even though we had no frost or ice on the fins, I restarted it late Saturday afternoon.
No other condition has changed and the fans still are not working. Yesterday morning it was back down to 34 and by late yesterday afternoon it rose to 37 (outside near 90). This morning it is reading 32!

 

[Gary521]

Forget the stock fans and add some new ones. Get a new thermostat too. Wire the fans and thermostat to the incoming 12 v supply to the fridge and add a fuse to that line. These things are inexpensive.
Check out this web site (search thru it ) https://www.arprv.com I will tell you where to locate the thermostat if you can't get to the stock location. The controller from this site is expensive so just use the info. There are thermostats that clip on and screw on. Some have added switches but I would rather it run by itself. If your fridge is cooling at night, it is a heat thing.

 

[BobTheBuilder]

This post is to possibly help others as so many of you have been so helpful to me this past year in fixing the little things on my absolutely wonderful Bighorn.

If you read below you will see last summer I was getting refrig temps in the 50's on hot days. I made plans to redo the baffles and add more fans but it got cool by the time I gathered it all up so the project sat all winter and spring.

Well I got busy this week as weekend temps were predicted to hit triple digits. As I sit here now it is 98 outside and the frig has not gone above the high 30's. Therefore, I will call the mods a success and give a description to the photos.

First of all I finally found the problem with the factory fans. The fuse that is between the 12V terminal and the relay was bundled with a group of wires (such that it could not be seen without cutting the wire tie off). That bundle was sitting at the bottom of the frame and when my ice maker pin hole leaks had been spewing water, the fuse had shorted. I replaced it, unbundled the wires and got the fuse up higher. The factory fans then worked correctly triggered by the thermostat but made only a slight improvement.

Heartland had installed two thin wood baffles--one at the top of the bottom vent opening to divert incoming air in to the coils instead of it going straight up inside the outside wall. The second one was attached to the top of the top vent opening and extended over to the top of the frig. I replaced both of them with metal ones made from thin aluminum flashing material (both shown in photos). For the top one, I bent a 90 and 1.5 inch down for the top one and was able to slide it behind the fins at the top. I made the top in two pieces so I could slide them out once they were in place and go the full 39" width of the refrigerator cabinet. I taped the joints with foil tape.

I added two auxiliary fans of squirrel cage design. Heartland also installed a steel sheet metal piece that blocks 2/3 of the upper vent (I assume to hopefully force the air all the way up over the fins before it could exit). I mounted the additional fans to the inside to this piece of sheet metal using screws and rubber grommets. I debated about putting them on a thermostat but instead opted for a rocker switch (like used in the coach for 12V lights, etc.) and mounted in inside the cabinet next to the frig.

After they were in place I added an extension made from the aluminum flashing to extend part of the way up the fins and used a piece of SS wire as a tie wire through the steel sheet metal to hold it inward against the fins.

Hope this helps others and I'll respond to any questions.

 

[danemayer]

Bob,

Thanks for sharing and for the pictures.

One other thing you may want to consider is to improve air circulation inside the refrigerator. Here's a fan assembly that mounts to the fins inside. Power comes from the light on the left wall of the RM1350.

 

[John T Bettencourt]

I had that same problem with my old Cedar Creek because the frig was on a slide and was in the sun all day. Go to Wal Mart and get a small elec fan put it on the bottom and plug it in with the frig let it run 24/7 problem solved

 

[JohnDar]

Bob,

Thanks for sharing and for the pictures.

One other thing you may want to consider is to improve air circulation inside the refrigerator. Here's a fan assembly that mounts to the fins inside. Power comes from the light on the left wall of the RM1350.

Added one of those from the 2013 Goshen Rally, along with a 2-D cell fan at the bottom the fridge. Keeps it cold. One of the fans gave out on the fin unit and I replaced it with a similar one from an old desktop computer I was getting rid of.


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