Escapees March/April 2016

the À ame is lit, the temperature sensor controls the process by making the À ame hot enough to drive the cooling unit process. When refrigeration is no longer called for, the temperature sen- sor puts the burner into a low- À ame mode that results in no refrigeration. Also, the manual control is a safety device that monitors the LP À ame and turns off the LP gas to the burner if the À ame is not lit. The second type is the automatic control. This type of control is easy to recognize because the operator uses an on/off switch to turn on the refrig- erator. The control takes over once the power is turned on. The automatic control is used on a majority of RV refrigerators due to convenience and the cost of manufacturing. Unlike the manual control, the automatic type of control requires a 12-volt power source. The following portion focuses on the automatic control. Refrigerator Temperature Sensor The refrigerator cabinet temperature sensor is generally a thermistor-type sensor. A thermistor-type sensor changes resistance based upon the physical temperature of the sensor. This type of sensor requires only two wires for proper operation. The refrigeration controller uses the resis- tance of the refrigerator temperature sensor to know when to turn on or off the cooling unit heat source. As a result, if the thermistor fails or is not located in the proper location within the refrigerator, the controller will not work properly. In some models, the thermistor is attached to one of the refrigerator compartment cooling ¿ ns. If the thermistor is not making good contact with the ¿ n, it can lead to the refrigerator cooling too much and freezing the contents. If your refriger- ator runs too cold, no matter what the setting is, check to see that the therm- istor is attached to the ¿ ns. A failed thermistor can cause the refrigerator to run too cold. If your refrigerator has a refrigerated cabinet temperature readout on the control panel, then it

“There are a number of tasks that the main controller performs in addition to monitor- ing the temperature sensor. Similar to the manual control, the automatic control must perform the safety task of knowing if the LP flame is lit or not.”

cooling unit compartment. Automat- ic-type controls require 12VDC power from your RV house battery to operate. There should be a fuse between the RV battery and the refrigerator controller. In addition, there is usually a fuse or two under the cover of the controller. If your controller is not working and you have tested for 12VDC power and ground to the controller, remove the controller cover and check the fuses on the circuit board. Warning: Before working on any electrical device, disconnect all power sources, including the shore power, until it is safe to perform tests. Consult a qualified RV tech if you are in doubt. There are a number of tasks that the main controller performs in addition to monitoring the temperature sensor. Continued ›››

is using the controller thermistor to determine the cabinet temperature. Using the refrigerator temperature readout is the simplest way to deter- mine if the thermistor is working or not. If your refrigerator does not have a cabinet temperature readout, trou- bleshooting the thermistor requires a table of resistance values versus temperature. If you know the physical temperature of the thermistor, you can measure the thermistor ohms with an ohm meter and compare the reading to the table of values. The thermistor values are supposed to be in the refrig- erator service manual. (My wife, Mao, and I post tables on the trouble-shoot- ing section of our Website.) The Black Box The main controller for the refrigerator is usually a black box mounted in the

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