Friday, September 7, 2012

Upgrading Dometic Fridge External Cooling Fans with Bypass Switch Installed

The 3-way fridge upper exhaust vent on Agile's and RS's is mounted lower than the top of condenser coil, making it not very effective in venting heat, an external fan(s) is really needed to assist with cooling. Our Dometic Fridge came with 2 (92-mm) external cooling fans forcing air to the condenser cooling fins, it runs rather noisy and draws too much power at around 0.36 amps each. The fans are controlled by a thermostat switch mounted to the condenser coil. The fans automatically turns on when it reaches a preset temp in the condenser coil , then turns itself off when condenser coil cools down.

I replaced both fans with a bigger (120-mm) and more efficient fans. I found one at our local Fry's Electronic store, it's made by Silenx (Amazon link: Silenx Effizio 120mm) . Current draw is only listed as 0.09 amp, very quiet at  12 dBA, and moves a decent amount of air at 44 CFM airflow (more specs. pictured below). I also added a bypass switch wired in parallel with the thermostat switch, this way I can run both fans continuously if I wanted.

Before starting, make sure to disconnect the fridge from 120-volt and 12-volt power supply. Measure if a bigger fan(s) will fit the back of your fridge, the 120mm fan is a perfect fit on mine. Remove the stock fans. Install a bypass switch and a 12-volt inline fuse (optional). Install the new fans using L-brackets (see pictures of install below).

2 Silenx Effizio 120mm fan


Fan specs.

Fabricated 4 brackets to join 2 fans side by side

To hold both fans firmly together, 2 brackets were used to both sides of the fan (see picture below).

Fans were mounted to back of fridge using L-brackets and parts from an "Erector" set. A metal strip and  L-bracket can be used as substitute.


Both fans perfectly working, you can't hardly hear them running.
LED illuminated bypass switch installed to front panel of fridge.

Picture of thermostat switch placement.

I also installed a heat deflector shield on top of the condenser coil. Notice the mini blade inline fuse holder (with red wire) to the left side of photo.

The heat stack exhaust was also fitted with a heat deflector to direct heat away from the condenser fins.

The only concern for me now is how  long the fans will last since it's rated for 8-12 volts and RV coach batteries can go over 14 volts when charging...will see. 
 
*UPDATE (2/4/14):
The fans have been working flawlessly for more than a year now. I only turn them on continuously during hot summer months, most of the time it runs intermittently in “auto mode”.

14 comments:

  1. To get the most from your cooling fans, you need to maintain them in order to prolong their lifespan. This means using them appropriately and minimally if possible.

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  2. Thanks for your very clear pictures & instructions here! I need to modify my fridge as it's not cooling as well as it should. The condenser coils are higher than the vent, so I think my best option is to install fans like you have. Can I screw the L-brackets directly to the back of the fridge without incurring damage?

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    1. I apologize for the late response. The original fans that came with the fridge has brackets that were screwed directly to the back of the fridge. I used short sheet metal screws for attaching the brackets or you could use short self tapping screws. The fridge metal skin/case is thin and that is where the screw will grab into, beyond that is just spray foam insulation. Avoid pre-drilling past the sheet metal skin just to be safe.

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    2. Ok, thanks! I'm realizing I need a new cooling unit now, though, because the fridge isn't cooling at all. After I have the new unit installed, I'll do the fan mod. You do great work, by the way - I've looked at some of your other mods!

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    3. Thank you. Sorry to hear that your fridge does not work, replacing the cooling unit is not cheap. Is the unit unfixable? You probably have tried this, try if it works on different modes...propane, shore power, or 12 volt (12 volt=needs engine running or plugged in to shore power to prevent depleting the battery). Does the boiler and condenser gets hot when fridge is on? Do you see any signs of ammonia leaks, ammonia odor, etc?
      You could try asking RV net forum members to help you diagnose what the problem is, some members are really knowledgeable on RV systems. Good luck.

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  3. I have tried that - also troubleshot thermistor, lower circuit board, upper circuit board, heat element, power going to all terminals on the boards, etc. The boiler, heat stack, condenser, and evaporator lines (the ones external to the unit that I can reach) all get hot. I may give RV net a try, though. Thanks!

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  4. Hello, great pics and instructions, I just purchased two of the same fans and they came with a three wire plug alone the a 2 wire jumper plug. I assume I will be cutting the three wire and 2 wire jumper plug off and wiring direct to a hot and ground source in the back of the refer. My question is, there are three wires and they are all black. How do I know which one to use for hot and ground and which one (the left over one) do I need to omit. Thanks in advance, Ed

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    1. Sorry for the late reply, I just got back from Yosemite NP and got no internet connection there. Anyways, if you look at the 2 wire molex jumper connector, the outermost wire is the positive and ground is the next wire towards the middle. I did not cut the fan wiring as the molex connector plugs right in into the existing fridge wiring. Image link to a molex wiring pinouts:http://wiki.robotz.com/images/4/48/Four_Pin_Molex_Connector01.png
      Hope that helps.

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  5. My 2007 SS Agile doesn't have a fan connection. Can you tell me where the +12v is coming from. I don't see a connection in the read of fridge. I haven't pulled the fridge out maybe there is a connection on the front panel. Thanks for any help.

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    1. Hi, it really depends on your fridge model. My Dometic RM8505 has a multi bus connector (with 12 volt power)on top of the fridge and can be accessed by removing the upper eyebrow panel.

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  6. Thank you for the fantastic, detailed photos. I'm using several EFX-12-12 SilenX fans to cool down my fridge and it's been working beautifully so far and is extremely quiet as well. It's been a lifesaver in this heat, appreciate your post on this!

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    1. You're welcome. My SilenX fans has been running for almost 4 years now, and yes they run extremely quiet and efficient.

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  7. Nice mod. Does the eyebrow panel in the fridge just pop out, or is removal more complicated than that? Thanks!

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    1. It is held by 2 screws located on the underside of the eyebrow panel, then the whole panel easily slides out.

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