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The second generation Dometic electronic system is a completely revamped system that made some dramatic changes compared to the first generation system. The eyebrow circuit board is more than a set of glorified switches. It has its own micro processor and communicates with the lower circuit board. The thermostat is replaced with a thermistor. The lower circuit board (main) activates the appropriate heat sources and has a micro processor to communicate with the eyebrow board. There are also some important changes to the gas control system in the second generation system.
The graphic below represents a generic version of the second generation electronics system. You can find the specific model numbers of the refrigerators included in this generation below. Also, the wiring shown here is the later wiring. Later models came standard with this wiring, and many older models were updated to this wiring with a wire harness kit, usually installed with a new circuit board (after the original one failed). The older wiring can be seen here. The wiring difference is in the thermocouple and gas control parts.
The main circuit board requires 12 volt to it for the refrigerator to operate on any heat source. In general, operation is started by the user pushing the power button "On" at the eyebrow. Depending on the eyebrow and the settings, a signal is sent to the lower (main) board telling it what mode to operate in. If "Auto" is selected, for example, the lower board knows to use AC (120 volt), if available, to heat the cooling unit. If AC is not available, the lower board knows to try to light the gas flame for the heat source. On models with a temperature control on the eyebrow, the setting initially starts at three. The user can adjust the setting up or down from there. A thermistor mounted inside the refrigerator on the fins in the lower box communicates the temperature to the lower (main) board by its varying resistance.
Standby Mode The main circuit board has two ways of coping with the failure of other system components:
1. If the eyebrow board becomes non-functional, the main board will go to Auto mode and select the best available heat source, with AC and Gas having priority. The temperature of the unit will be kept in the middle position. This depends a little on why the eyebrow board is non-functional. If the eyebrow were disconnected, for example, the refrigerator would not work.
2. If the temperature sensing system fails, the board would cause the refrigerator to cool continuously in the mode selected by the eyebrow. In other words, the refrigerator will not shut down as long as power is available. Usually the thermistor needs to be changed when this happens.
Models included in the Dometic second generation electronics: S1521, S1531, S1621, S1631, S1821, S1831, RM2607, RM2611, RM2612, RM2620, RM2652, RM2807, RM2811, RM2812, RM2820, RM2852, RM3607, RM3662, RM3663, RM3807, RM3862, RM3863, RM4872, RM4873, RM7030, RM7130, RM7732, RM7832, and NDR1062.
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