Why Fridge Defend Fan Controller is Superior for Dometic and Norcold RV Fridge

This page teaches why the advanced Fridge Defend + Fan Control along with the blower fan ventilator kit is a necessity on both Dometic and Norcold RV refrigerators.

Why would you need a Fridge Defend + Fan Control?

Common Questions: Can RV fridge fans prevent my boiler from overheating; do I really need the Fridge Defend by ARP Control?

Answers: No & Yes!

First the No: RV fridge fans have a very small effect on the boiler temperature your Dometic or Norcold fridge. This is because the boiler is insulated and has heaters within the insulation. Cooling unit fans do not change the boiler temperature, if they did, your fridge would not work properly.

Now the Yes! At minimum you need the Fridge Defend without Fan Control (v4.0), even better the Fridge Defend + Fan Control (v4.1) with 12V RV fridge fans which will help increase the efficiency of your fridge in addition to providing RV fridge defrosting if fans are mounted inside the refrigerator compartment as shown below.

RV Exhaust Fan

We will explain why you may want the Fridge Defend + Fan Control using the following two drawings, one side vent and the other a roof vent cutaway.

Roof Vent Cutaway Drawing

The best reason to use the Fridge Defend + Fan Control is to improve efficiency of your fridge by the following methods:

  • Circulation of Cooling within Fridge Increases Efficiency: Our fan controller only runs when it is needed, that is when refrigerant is being produced. A fan inside your fridge controlled by our controller takes the hot air off the top of your fridge and cools it on the cooling fins thereby increasing efficiency and helps shorten the time the cooling unit runs. Further, the fans turn off when they are not needed, if the fan inside the fridge runs all of the time, it results is losses within the fridge that requires the cooling unit to run too much.

    Click Here for Fridge Internal Blower Fan Details
  • The Fridge Defend + Fan Control keeps your Cooing Unit Efficient: by keeping a constant supply of cool air, and sucking out the hot air within your cooling unit compartment, your fridge runs much more efficient.

RV Fridge Side Vent Fans

Side Vent Cutaway Drawing

  • Factory Fans Fail: The factory installed fans can fail and you have to remove your fridge to replace them in most installs. The factory fan switch usually degrades in accuracy over time so that the fans either never run or run all of the time. The factory fans can re-circulate the hot air within the cooling unit compartment in conditions described below, thus they do not remove the hot air when the fridge needs it most.

  • Precision Fan Switch Fridge Defend + Fan Control has a precision 2% remote sensor that can be mounted in the best place on the cooling unit. In addition, the controller can control up to 5 Amps of fans thereby giving you the ability to use multiple fans.

  • Fully Adjustable ON/OFF Setting: The Fridge Defend + Fan Controller is fully adjustable for the temperature at which the fans turn on and off. This gives you full control, no more wasting precious electrical energy while having a warm fridge.

RV Fridge Cooling Fans

Why RV Fridge Cooling Fans -- Wind Cooling Stagnation

The front view of an RV with a side wind drawing shows the dynamics of air flow across your RV when the wind blows. If the wind is blowing from the opposite side of your RV from the location the fridge is installed, then you could be suffering cooling unit ventilation stagnation. In short, as the wind hits the RV from the right of the figure, the air has to compress to go over the top of the RV. On the downwind side of the RV, an eddy is formed by the wind currents. This can cause stagnation or re-circulation of the hot air within the cooling unit compartment. The Fridge Defend by ARP alone (without fan control) will protect the fridge in this situation. But, having the Fridge Defend + Fan Control will evacuate the hot air faster. The result, wind gusts that would result in the fridge boiler over heating can now be resolved faster, how? We cannot claim to be able to use a fan to overcome mother nature, but what we can do is turn off your fridge when the boiler starts to overheat and use fans to help get that hot air out of the cooling unit compartment by pulling in cool air and sucking out hot air.

Fan Air Recirculation

Fan Air Recirculation

Please note that the first figure on this page shows how the factory fans recirculate the air. The figure to the right shows a helicopter that has the phenomena called ‘Vortex Ring State’. This is when the helicopter blade sucks back into the blade the same air that was pushed out of the blade. Vortex Ring State prevents the fan blade from moving the air, which results in the crash of the helicopter, or for your fridge the air from not being moved out of the cooling unit. This is why we use blowers rather than fans, and we mount the blowers where they can be most effective.

RV Fridge Fan Sensor

Installation of Fan Sensor

This next drawing shows a typical RV cooling unit arrangement. Please note that the factory typically installs a snap-switch to control the fan just above the flue tube on the condenser. Not only is this a bad place to control the fan, it tends to overheat the snap-switch which results in failure. In addition, the factory fan is installed in the middle of the fridge; this location can recirculate the hot air which results in no cooling at all in hot weather.

Norcold 1200 Fan

Fan Sensor Location

We recommend attaching the Fridge Defend fan sensor to the absorber coil as seen in the image to the left. The absorber coil is easy to get to because it is seen from the lower cooling unit access door. In addition, the absorber coil only heats when the refrigerant is being produced by the boiler, thus the fans only run when needed rather than wasting energy by running a fan when it is not wanted or needed.

Depending on your fridge the sensor can be mounted on the bottom, or second from the bottom absorber coil. On some fridges the bottom absorber coil gets very hot, in this case the fan sensor can be mounted on the second from bottom absorber coil so the fans is easy fine tune combined with the adjustments listed below.

This is a summery for instillation, user must download and follow Fridge Defend instillation instructions PDF

Fan Setting ON Temperature °F OFF Temperature °F
000 Fan Is Off Fan Is Off
001 90 75
002 100 85
003 110 95
004 120 105
005 130 115
006 140 125

ARP Fan Adjustment v2.1 to v3.1

The table on the left is the fan setting chart found in the Troubleshooting Guide supplied with the purchase of the ARP Fan Control. Just put the ARP into the Setup mode (see PDF manuals or video) and change the setting, this gives you control over your fans :)

Fan Setting ON Temperature °F OFF Temperature °F
0 Fan Is Off Fan Is Off
1 110 95
2 115 100
3 120 105
4 125 110
5 130 115
6 135 120

ARP Fan Adjustment v4.1 to v5.1