Adding Cooling Fans at the Top of the Refrig Chimney:
For safety: Before you begin working on your RV refrigerator unplug the 110 volts to your refrigerator. There's a plugin at the back of the refrigerator. Also remove the 12 volt fuse from your fuse box that runs to the refrigerator to keep from blowing the fuse. If you don't have spare 12 fuses now's a good time to order fuses and a fuse puller (listed below).
At the end of this write-up is a list of materials you may need/want to order before you get started.My refrigerator is installed at the back of the trailer (not in a slide out). So I have relatively easy access to parts of the back of the unit.
Here's a pretty good diagram and video about how your absorption refrigerator operates:
"How does Dometic or Norcold RV Fridge Work?* "
https://www.arprv.com/how-dometic-no...the%20fridge.*
Using your refrigerator model number (located on a label inside the refrigerator) find your refrigerator service manual.
Mine is a model N8X.
Google*search = "Norcold N8X Service Manual".
The service manual contains wiring diagrams, operating instructions and a troubleshooting guide.
All of these page references are from my N8X Service Manual. Your mileage may vary.
Page 12: Description of 12v condenser cooling fans, the cooling fan (if installed) turns on at 130 deg F / off at 115 deg F.
NOT contained in the service manual is this description: IF installed, the condenser cooling fan is enabled, via a thermostat, by 12 volts anytime the front panel power switch is turned on. The only thing that turns the condenser cooling fan on/off is the snap ring thermostat attached to the condenser that is set to turn on at 130 deg and off at 115 deg.
I was unable to locate a signal line on the refrigerator controller I could use to enable the cooling fan only when the refrigerator was in refrigeration mode (either gas or electric). (The refrigerator evaporator thermocouple could provide this signal but it's voltage is only 3.3 volts and I suspect any attempt to tap into that line would change the impedance enough to alter the way the thermocouple circuitry functioned.)
According to the "Wiring Schematic" on page 55; K1 is a relay that applies a 12 volt signal to pin 6 of the 16 pin connector anytime the refrigerator is turned on. Pin 6 is the 12v signal and Pin 1 is ground. This 12 volt signal is used by several "optional" devices that might be installed on your particular model unit. I had no wires connected to pin 6 or pin 1 therefore I had none of the optional devices (such as a cooling fan or cold weather heater or ice maker, etc). Each of those optional devices are separated from Pin 6 by either their own thermostat or an on/off switch.
Installing your own condenser cooling fan:
Disconnect the power to your refrigerator (120volt and 12 volt fuse). Remove the controller board. I soldered a 15 inch length of 22 gauge stranded red wire to pin 6 and a black wire to pin 1 (ground). I then hot melt glued these wires to the edge of the controller board to act as a strain relief. I reinstalled the controller board. (see photo)
Just below the controller board assembly I installed a Solid state relay and connected Pin 6 to lug #3 of the relay and Pin 1 to lug #4. I spliced into 12 volts and attached 12 volts to lug #2 and lug #1 I connected to the snap ring thermostat that feeds the fans. Reason for the solid state relay: I'm not certain the power capability of the K1 Relay and the 4 fans I installed consume a total of 1 amp of power. Rather than risk damaging the K1 Relay, I decided to have Pin 6 trigger a Solid State relay that only requires 30 milliamps to trigger. The relay then applies 12 volts to operate the fans anytime the refrigerator is turned on. I probably didn't need to do this since K1 is designed to feed several optional devices and none of them are installed on my unit. 12 volts on my trailer is white wire with a pink stripe and ground is a white wire.
Condenser Cooling Fan and Thermostat:
When factory installed, the thermostat is screwed to the fins of the condenser. I couldn't reach down far enough to attach it so I opted to install an adjustable snap ring thermostat and attach it to the 1/2" copper tubing that runs along the top of the condenser coil. I attached it using 14 gauge copper wire, it's very flexible. I set the adjustable thermostat to come on at 90 degrees. It will then turn off at 70 degrees. That was a mistake. I should have set it at probably 105 degrees. I live in Kansas and it's July, and it hasn't been below 75 degrees day or night for the past 2 months. So, my new fans run 24x7. If I ever take the chimney cover off again I'll reset that to 105 degrees (they will turn off at 85).
To gain access into the chimney, you will have to remove the cover on the top of your chimney by removing the 4 screws that hold the cover on. You'll have to dig off the caulk that covers the screw heads and later replace the caulk when you recover it. Below the cover is an aluminum insect screen. I couldn't get it off without destroying it so I had to make a new one (described below). BTW, when I opened the top there were two small wasp nests (not mud daubers) who greeted me when the top came off. They were gaining access through the three vents at the bottom access cover. I have now covered those three vents using the screen kit listed below.
I installed a total of 4 fans by drilling 4" diameter holes in 3/4" plywood. The fans really needed 5" diameter holes but the chimney opening is only about 5 1/4" so my fans aren't running at full capability because they are partially blocked. But with 4 fans there's a lot of air moving up through the back of the cabinet.
I then installed the adjustable snap ring thermostat (using copper wire) and the plywood/fan assembly into the chimney with screws and put the new screen and cover back on. I installed my new homemade mud dauber screen using the "Amerimax Lock-in Gutter Guard White" screen listed below. I set it over the chimney and screwed it into the plywood so it can be removed. I also installed the three new screens at the bottom access cover. Plugged the refrigerator into 120 volts and installed the 12 volt fuse, and turned on the refrigerator. The fans came on.
Over the next several days I ran temperature profiles. My refrigerator has 5 temperature settings indicated with a * (star) that is displayed. Five stars is the coldest and 1 star is the warmest. I set it at 2 stars. I slid the thermocouple located on the refrigerator cooling fins to near the top of the fins (closest to the freezer). I installed two remote temperature sensors, one in the refrig and one in the freezer. They transmit the temp to a station sitting on the counter in the trailer. I also have an infrared laser thermometer and measured the actual temperature of the thermocouple to compare to the temp of the temperature sensors. I also measured the resistance of the thermocouple to see how it varied from day to day. The refrig had been running for 24 hours before I started this process.
See the photo of the results of the refrigerator profile test.
According to the service manual the refrigerator evaporator coil thermocouple should show these readings at various temperatures. My particular thermocouple appears to have consistently high resistance readings but it does change with temperature so I'm just going to leave it alone.
IN SUMMARY - DO YOU REALLY NEED TO DO THIS!
All in all it was an interesting project and I think I'll leave the Acurite temp probes in the trailer whenever I'm traveling just to keep track of how things are working. One of these days I may unplug the cooling fans and repeat the temperature profile for comparison. I can do this by simply removing the wire connected to Lug #1 of the solid state relay and the fans will be disabled, but the air flow will be reduced because the fans are restricting air flow somewhat.
I originally started this project just trying to add screens to block mud daubers from gaining access. However, in that process I created a couple of other problems that resulted in my refrigerator not working as well. So, after reading posts of many other users on the forum I decided to add not only insect screen but install some cooling fans.
To determine if you really need to do this you might start by purchasing the "AcuRite 02082M Home Temperature & Humidity Station with 3 Indoor / Outdoor Sensors" (listed below) and conduct your own temperature study. Then set a fan blowing air into the air inlet of your refrigerator and repeat the thermal profile study. If there's considerable improvement it might be worth your effort to install these fans.
Best of luck, thanks to many of you who helped by posting ideas and comments when I was first trying to figure out what was going on. Here's a link to the original post that led to this "exercise".
https://www.crossroadsowners.com/for...hot-15428.html
(now all I have to do is figure out how to attach all the pictures)
Happy Camping!
Dustin
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THINGS YOU'LL NEED BEFORE YOU GET STARTED:
Strong Quiet 12025 Fan 120x120x25mm 12cm 120mm Computer Case Fan DC 12V Cooling Fan for Computer case 2Pin 2 Wire 1600RPM 2-Pack
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
FIRMERST 16/2 Low Voltage Landscape Lighting Cable 100 Feet UL Listed
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
TWTADE SSR-25 DD 25A DC 3-32V to DC 5-60V SSR Solid State Relay
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
The wiring diagram shown in the Amazon description for the solid state relay is wrong; Pin 2 should be your + 12 volt input; Pin 1 is the Load (that goes to your snap ring thermostat and fans). Pin 3 is the input positive (goes to Pin 6 of your controller) and Pin 4 is the input negative (goes to pin 1 of your controller (ground)).
Adjustable snap ring thermostat; 20 degree hysteresis; 90 to 130 deg F
Emerson 3F05-1 Adjustable Snap Disc Fan Control
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
Set the Adjustable snap ring thermostat to 105 degrees. It should shut off at 85 degrees.
Here is the Norcold Fan thermostat that turns on at 130 deg F / off at 115 deg F: Norcold 618093 DC Fan Thermostat - Fits All Models with Fans
https://www.amazon.com/Norcold-61809...s%2C290&sr=8-5
Alpha 1021 Self Leveling Sealant (for flat surfaces) (same as Dicor lap sealant):RecPro 1021 Self-Leveling RV Sealant 11 oz. (1 Pack)
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
LotFancy 22AWG Stranded Wire, 6 Colors (30 Feet Each) Electrical Wire, Tinned Copper Hookup Wire Kit 22 Gauge 300V for DIY, Flexible, PVC insulated, UL Approved
https://www.amazon.com/LotFancy-Stra...xpY2s9dHJ1ZQ==
I soldered all the connections and covered them with shrink tubing. If you solder, I suggest you use flux on the wires prior to solder. This will make soldering much easier.
Dual Wall Adhesive Heat ShrinkTubing Kit:
https://www.amazon.com/270-pcs-Adhes...aWNrPXRydWU=**
RV Furnaces Bug Screen, Heavy Stainless Steel Mesh Flying Insect Screen with Installation Tool,
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
I attached these with electric fence wire rather than the included spring clips that came with the kit.
Electric Fence wire:
I attached all the Steel Mesh screens using Electric Fence wire (rather than the included spring clips). Most farm and ranch stores, Ace Hardware. High tensile strength, galvanized.
Amerimax*Lock-in Gutter Guard White Item #1930567Model #6363* * $3.00
https://www.lowes.com/pd/Amerimax-Lo...ite/1001838926
I found this at Lowe's. It's in the rain gutter department. As purchased it's about 5" wide and 36" long. Unfold the bent edge and use a rubber mallet to flatten the expanded metal until it's about 7" wide. Now you can reshape it to fold down over the refrigerator chimney. Using tin snips cut the corners to allow the edges to fold down over the*chimney. You can cut the metal with tin snips or a cutting blade on an angle grinder. You could also cut and bend this same screen (sold in white or black) to block mud daubers from entering various areas of your trailer. Attach it with electric fence wire (galvanized so it won't rust).
25 Pack 15 AMP ATC/ATO Standard Regular Fuse Blade 15A Car Truck Boat Marine RV
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
Also a fuse puller:Walmeck Blade Glass Fuse Puller Insertion Tool Standard ATS Car Feses Box FUP2
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
AcuRite 02082M Home Temperature & Humidity Station with 3 Indoor / Outdoor Sensors,
https://www.amazon.com/AcuRite-02082...-garden&sr=1-8
Laser Infrared Thermometer Temperature Gun
https://www.amazon.com/Etekcity-Lase...088748&sr=8-10
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Linear Mode
