The Great Refrigerator Fan Modification Project

The original refrigerator fan in our 2011 Casita Spirit Deluxe started making dreadful groaning noises, and would run for hours, with no appreciable effect. We discovered that the brackets holding the fan to the side of the Casita had become loose, allowing vibration and enhancing noise. For what appears to be a computer fan, it is extremely heavy, with only two brackets on only one side of the fan providing minimal support. We believe the weight of the fan on brackets, combined with vibration loosened the mounting.

The noise was maddening, and non-stop. The fan sucked power and our 90 watt solar panel was just barely keeping battery voltage over 12.4. We decided to get rid of the old fan and replace it with a new one. The problem, though, was two-fold.

Nowhere in the official Dometic Operation and Installation Manual is there any mention of the cooling fan. Despite the fact that the fans are marketed with the name and stock number by Dometic, there is no reference to the fan whatsoever.

Casita offers the fan as an option.  Despite this, there is no mention whatsoever about the fan in the Casita Owner’s Manual. When we went through Casita’s briefing, we were told nothing about the fan other than ‘here is the switch to turn it on and off.”  So we are flying blind, essentially.

The original fan was set about 9 inches below the cooling fins of the Dometic fridge (RM2454). When running you could not feel much air flow over the fins. Removing the plenum (the cover) made little difference.
We found a replacement fan kit on eBay. Provided by a small private company, RV Cooling Unit Warehouse in Memphis, TN, it featured a custom steel bracket; a piece of sheet metal about a foot long and 1.5” wide; and two smaller fans. The fans are wired for Casitas and the thermostat is built into the wiring harness. There were no mounting instructions, and only bolts to mount the fans to the bracket were included.

Casita Travel Trailer Fan ModificationAt first we planned on using the supplied bracket but we realized that it was no better than the original brackets in providing stabilization or support of fans. In addition, we had to bend the new bracket wide enough to accept the fans. We are convinced the motion of the camper while being towed allowed the fan to wobble up and down at the unsupported end, and the new bracket would not have prevented this.

So we decided to install TWO brackets, one in front attached to the molding for the upper refrigerator vent cover, and the second in the rear, for additional support.

We decided to create a diagonal brace to be the main support for the two brackets. The diagonal brace attaches to the camper wall using one of the same holes drilled through the fiberglass to support the original fan. Measuring that distance is a bit inexact as the wall is curved and the belly band is between the opening to the fins and the holes.

Casita Travel Trailer Fan ModificationBefore I go any further, I want to remind you that every Casita is a little different. I’m betting my lunch that there NO measuring was done when Casita installed the fan in ours. It was undoubtedly a situation where the guy with a drill and a fan merely drilled a pair of holes just any old place between the upper and lower compartments. In our case it was 9 inches below the fins-much too far to make any real difference in heat diffusion/cooling.
So please take this into account and, remember:    YMMV… Your Measurements May Vary.

Because each Casita is a little bit different in the placement of the original fan, AND the side of the Casita has a slight curvature to it, one must make a precise measurement from the mounting holes and the molding where the bracket is mounted.

We measured from the outside. Don’t forget to take the belly band into account, because it sticks out 1 – 1/16th of an inch (measure yours!) and may throw your measurements off. The lower bend in and length of the brace will account for this slop.

Uncap the rivets holding the original fan in place.  The rivets will be replaced with a 10-24, 1 – ½” stainless steel machine screw. The rivets will need to be drilled out. They are held in place by acorn nuts. Prevent the acorn nuts from turning by holding them in place with a 7/16th wrench or socket.

Retain the caps and plastic washers because the washers protect the gel coat from being crushed. When you screw them back in, be careful not to over torque them for the same reason.

Remove the original fan by drilling out the original rivets from the holes underneath the upper compartment. Cut the wires as close to the fan as possible. Install connectors at the ends of these wires for the new fans. Blue is ground, red is hot. By tying into the original wiring for the fan on/off switch (inside the cabin), the wiring is incorporated into the new system.

The wiring from the thermostat to the fan and the refrigerator/gas assembly in the lower compartment runs inside the right vertical edge of the lower compartment. Be very careful when cutting the zip ties holding the wiring in place. You will want to zip tie them back where they were at the end of the installation.

The wiring harness for the new fans has connectors for hooking to the refrigerator DC power, but, as noted above, it was easier to remove them and connect them to the cut wires going to the old fan. We used plugs to make it removable but splices or twist nuts will work just as well. We also spliced in extensions to make sure there was enough slack.

Image Gallery
(click image to see larger version)

 

 

Fan Brackets:
Making the support brackets was relatively easy. The fans have pre-drilled holes in the plastic frames, and in this case, were 3 – ¼ inches on a side between holes (total length of fan is 3 – ½”). Make sure the rear bracket opens downward in order to clear the diagonal tube that descends from the fins. File off any burrs from drilling the holes.

Place the fans about two inches apart, and make sure the wiring is in the gap between the two. The molding holes will automatically determine where the bracket will be mounted to the camper. Use 10-24 – 1 – ½” machine screws to attach the fans to the brackets. We put the screws with the heads on the top side so that, in case a locknut falls off, the fan still stays connected to the bracket. Secure with locknuts.

Choose one of the two existing holes for the lower brace attachment. We chose the left (aft) hole because the right hole would have required a longer rear bracket and would have been quite a bit off center. Drill the hole in the rear bracket for the upper brace attachment directly above the hole you chose for the lower attachment.

Measure from the holes below the upper compartment to the molding. This will be your basic measurement for the brace.

Manufacture the brace from the 1” aluminum stock. Two 45 ̊  bends in the aluminum will form your attachment points. The upper 1” arm attaches to the rear bracket, the lower 3” (or more, it’s your choice) arm attaches to the interior wall of the camper. This lower bend is the most important, because you must take into account the curvature of the wall. In our case, the brace bends were approximately 45 ̊ (degrees) and were bent in a bench vise and modified a bit to fit properly.

Install the brace (the 1” end) to the rear bracket. Properly manufactured, the diagonal portion of the brace will run towards ~190 degrees, or towards 7 o’clock. The middle length of our brace was approximately 7 – 3/16”, or a hypotenuse of 7.34.

Temporarily install the assembly (brackets with fans attached) to the molding. You need to find exactly where the brace needs to be at the lower attachment point (the holes in the side).

The easiest way to find where to drill the hole on the lower, 3” end is to stick an extra fine tipped Sharpie in through the hole from the outside, while your assistant holds the brace against the hole on the inside, in order to make a mark on the aluminum. A punch serves to make an indentation on the aluminum to prevent the drill bit from skipping on the metal. File off the burrs to make a nice smooth finish.

Remove the assembly from the camper in order to drill the hole in the 3” long section.

Once you have the lower hole drilled in the brace, install the completed assembly.
Connect the wires.

The wiring that came with the fan includes a thermostat. Keep the thermostat in the vicinity of the fans. We put it so that it hangs in between the two fans but it could also be placed directly on the fins.

Test the fans by using a hair dryer to blow hot air on the thermostats. They should start up relatively soon.

Use locknuts to firmly attach the brace to the wall and the bracket assembly to the molding. Do not forget to replace the plastic washer on the exterior of the Casita. Be careful not to crush the gel-coat, but still screw the locknut firmly to prevent movement.

Install a 10-24 – ¾” screw and the plastic washer in the unused hole. Replace the caps and, if you are so inclined, dab them with a little silicone.

Replace the plenum (cover) and you are done.

Postscript:
After installing the new fans, we spent a week camping in extremely hot weather (low 90’s). We towed the camper over some washboard roads and upon checking found that the fans and bracket assembly had not moved. The new fans ran much more quietly but we didn’t see much decrease in the length of time they ran.

Fan Mounting Assembly Schematic:
fan-mounting-assembly

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List of Materials

Fan kit from RV Cooling unit warehouse:
2 – 12v PC fans with wiring harness and thermostats

1” aluminum angle stock for fabricating:
Front bracket: 12” long
Rear bracket: 10” long
Diagonal brace: 3/4” aluminum flat stock
1/8” thick
12” long
Hardware:
8 stainless steel machine screws, #10-24 1 ½”-attach fans to brackets
5 stainless steel machine screws, #10-24 ¾” connect brackets and brace to wall
and molding.
13 locknuts for above

Wiring:
2 sets connectors for 22 gauge wire
small diameter zip ties

Tools required:
One shop minion (assistant)
7/32nd drill for bracket holes
3/16ths drill for removing rivets
7/16th socket or wrench to hold acorn nuts
3/8” ratchet socket (for locknuts)
Cross tip screwdriver (for machine screws)
Flat tip screwdriver (to remove cover to fins)
Small wire cutter
Hammer and center punch (for locating holes on brackets/brace)
Square/tape measure
Electricians tape
Extra fine tip Sharpie
Fine toothed file for removing burrs