Thermocouple; Burner; Flue Baffle; Flue Cap - Dometic RM2351 Diagnostic Service Manual

7.3 thermocouple

The Thermocouple is a component that extends over
the burner assembly so its tip is in the path of the flame.
During normal gas operation, the thermocouple should
produce 25 to 35 millivolts when connected to the lower
circuit board. Any reading below 18 millivolts could cause
erratic gas operation. note: A reading of 18 or less could
be caused by low gas pressure, carbon build up or im-
proper thermocouple location. The thermocouple should
be centered over the burner and extend over 3 slots. The
control board reads negative millivolts from the thermo-
couple and the positive lead goes to the ground terminal
on the control board or ground strip.
note: A rapid on/off of the switch or a brief interruption of
DC power source does not allow the thermocouple time
to cool. When the power is restored, the thermocouple
has not cooled completely and the check light may come
on. Turning the refrigerator OFF–ON while operating in
the gas mode may cause a check light. The new lower
control has built-in delay when the unit is first turned on.
If the lower control reads millivolts in excess of 6 MVDC
the control will go into a 30 second gas delay before at-
tempting to light on gas. To test the thermocouple set the
meter to DC millivolts. Put the black lead from the meter
to terminal J3 ( original board ) or J4 ( current board ) and
the red lead from the meter to J10 or other lead from ther-
mocouple. Start the unit on gas and measure the DC mil-
livolts produced by the thermocouple. The thermocouple
should produce 22 to 36 millivolts within 45 seconds. If
the millivolts are 20 or below erratic operation will occur.
Anything below 10 to 13 the control board will not keep
the gas valve energized and turn on the check light after
the 45 second trial-for-ignition.

7.4 Burner

The slots in the burner should be directly below the flue
tube. The burner should be cleaned periodically, at least
once a year. Soak the burner in an alcohol based solvent
and allow to air dry. If the burner does not have a good
ground it can cause erratic gas operation. The electrode
sparks to the burner tube and a erratic ground will cause
erratic gas operation.

7.5 Flue Baffle

The flue baffle ( spiral baffle ) is a twisted piece of metal
that hangs in the flue tube to slow the heat from the flame
to the proper location on the cooling unit. If the flue baffle
is too high or low the heat will not be transferred to the
cooling unit properly.
Baffle
MODEL ABOVE
BURNER
RM2351-4 1-15/32
RM2451-4 1-15/32
RM2551-4 1-15/32
RM2652 1-7/8
RM2662-3 1-7/8
RM2852 1-7/8
RM2862 1-7/8
Lack of heat transfer to the cooling unit will cause low cool-
ing performance in the gas mode. It should be cleaned
periodically, at least once a year. The proper position of
the baffle above the burner should be as shown in the
chart : always refer to parts list on the model/product
number unit you are currently working on.

7.6 flue cap

The flue cap is located at the top of the flue tube and is
attached with a screw or pushed down over tube. Not all
units will come with a flue cap. The design of the baffle
wire in the flue tube will slow down a down draft.

7.7 flue tube

Carbon build up will not allow the heat transfer to the cool-
ing unit and cause lack of cooling on gas. The flue tube is
welded to the boiler of the cooling unit. In a rough riding
coach there have been rare cases where the weld will
crack and create lack of cooling. The flue tube must be
cleaned periodically, at least once a year. Clean by using
a flue brush, Dometic Part No. 0151404001.
20
SIZE
3-15/16X25/32
3-15/16X25/32
3-15/16X25/32
5-1/8X13/16
5-1/8X13/16
5-1/8X13/16
5-1/8X13/16