Dc Voltage; Dc Voltage Requirements - Dometic RM1350 Diagnostic Service Manual

The resistance should be 4.0 Ohms +/- 10%. The resis-
tance can also be checked directly at the motor assembly.
This will require removal of the plate along the back wall
of the freezer just behind the ice bin.
SectIon 4 dc Voltage
Clean Direct Current (DC) power is mandatory for high-
tech circuits to operate as designed. A battery will provide
straight line DC power. The converter and alternator pro-
duce DC power by a series of diodes that rectify alternat-
ing current to DC. The Dometic control system will only
tolerate up to 6 AC volts on the DC line. AC ripple can be
measured by a digital voltmeter set on the AC and mea-
sure at the main DC terminal block connections. Six volts
AC or less is acceptable. If AC volts exceed 6 on the DC
incoming line, the power source should be cleaned up.
AC voltage in excess of 6 volts will affect the processor
and create erratic operation. When testing for AC ripple
on the DC line, always put a load on the converter. The
operational range of the unit is a minimum of 9.6 volt DC
to a maximum of 22 volts DC. The unit will automatically
shut down at 22 DC volts or greater, and come back on
when voltage has decreased to 18 volts DC. The refrig-
erator requires at least 9.6 volts DC for proper operation,
however the panel lights will continue to be illuminated
until voltage has dropped to 4 volts DC or below. Do not
use the body or chassis of the RV as a substitute for ei-
ther of the two conductors. The refrigerator must be con-
nected to the battery circuit with two wires of adequate
capacity to avoid voltage drop. Proper polarity is crucial
for refrigerator operation. No other electrical equipment
or lighting should be connected to the refrigerator circuit.
Just because you can read volts, does not mean you have
the amps to operate the control system. If relays buzz or
lights go dim or out during operation, this could indicate
there is a loose connection somewhere. As a last test, use
a battery and run wires directly to DC terminal block. If the
unit works ok on direct DC volts from a battery, the prob-
lem is in the coach not the refrigerator control system.
Main Terminal Block
12 V dc alternator (d+) connection
The refrigerator requires a continuous 12 V DC supply to
maintain operation of the control system. Furthermore, for
models equipped with the automatic door lock, it requires
the connection of a signal wire from the alternator (D+) to
maintain the automatic door travel latch and the tempo-
rary gas lockout function. The vehicle's alternator (D+) is
connected to D+ on the terminal block.
grounds
The operation of the Dometic refrigerator is also depen-
dent on good, clean ground connections. Loose or corrod-
ed ground terminals create an unknown resistance factor
that can effect the voltage detected by the Power Module.
A loose negative DC wire will create a negative millivolt
signal that the control board will pick up and create erratic
operation. Check the integrity of the grounds from the re-
frigerator all the way to the power source/battery. Clean or
tighten any suspicious looking connections.
note: The DC terminal block below the control boards
should be cleaned and tighten at all 6 wires.
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