Dometic RM7732 - Manual (Page 13)

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DOMETIC® RM7030/RM7732
Refrigerators
DIAGNOSTIC SERVICE MANUAL
5.2 THERMISTOR
RM7030 (Prod. No. 921890401) and RM7732
To determine if the temperature sensor is functioning
properly, perform the following test.
Remove the cover from the lower circuit board. Discon-
nect the thermistor harness from the P2, 2-pin terminal
on the lower circuit board. Place thermistor in a glass of
ice water. Wait 2 to 3 minutes. Using an ohm meter,
place a probe on each terminal point. You should get a
reading of approximately 7,000 to 10,000 ohms. Normal
failure for this type of device is to have a very high
resistance. A defective thermistor could cause an over-
cooling condition on all modes.
5.3 THERMISTOR ADJUSTER
RM7030 (Product No. 921890401) and RM7732
The thermistor adjuster is a resistor-type component
that attaches between the thermistor and the lower
board. Its function is to allow the refrigerator to reach
temperatures below the normal 46° to 35°F. range
(setting 1 through 5 on upper circuit board).
To determine if the thermistor adjuster is operating
properly, do an ohms resistance check across the
terminals. Proper ohms reading is approximately 23,200
ohms ± 10%.
5.4 SOLENOID VALVE
A. RM7030 (Product No. 921890201 & 921890301)
The solenoid valve assembly is a safety valve as well as
a gas flow valve. When the AES selects LP gas opera-
tion, DC volts are sent to the solenoid coil which opens
the internal valve.
Check the solenoid coil with a properly
calibrated ohm meter. Remove the
connector from the solenoid
and measure the resis-
tance across the upper
and lower terminals. The
proper reading would be
20 ohms with a toler-
ance range of ten
percent. Once flame is
lit, the thermocouple
produces the voltage to keep
the valve open. If for any reason the thermocouple does
not provide enough current to the valve, it will close,
stopping the flow of gas. To check this portion of the
solenoid valve assembly, verify the thermocouple is
good (see Sec. 7.3A), the tip is clean and the receptacle
in the solenoid valve assembly is clean. If the thermo-
couple checks good, then replace the solenoid valve
assembly.
NOTE: If the solenoid ohms check shows an open coil,
the refrigerator will not operate on any mode.
P2
THERMISTOR
ADJUSTER
TO THERMISTOR
NOTE: Dometic refrigerators do not come equipped with a
thermistor adjuster. This is an add-on component.
THERMISTOR
ADJUSTER
TO THERMISTOR
B. RM7030 (Product No. 921890401) and RM7732
When the refrigerator selects LP gas operation, DC
volts are sent to the solenoid coil which opens the
internal valve.
Check the solenoid coil with a properly calibrated ohm
meter. Remove the connector from the solenoid and
measure the resistance across the terminals. The
proper reading would be 49 ohms with a tolerance
range of ten percent.
P1
P2
P3
Thermistor
unplugged
from PC
Board