Dual Solenoid Gas Valve; Burner Head, Electrode & Valve Assembly - Atwood 79 Series Service Manual

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Dual Solenoid Gas Valve

Valve
Volt-ohm meter
coil
30 to 50 OHMS
Burner Head, Electrode and Valve Assembly
79-II, 85-IV
1522, 2334
enclosed
NO
DEFLECTOR
8531 & 35-III
85-III -16, 20, 25
OPEN
-12VDC
Power from
Ignition Control
Shut off power
before servicing
+12VDC
(red wire)
89-III
2540
OPEN
DOUBLE MESH,
NO DEFLECTOR
LARGER PORT HOLES
OPEN
We use a White Rodgers dual solenoid gas valve on all of our
furnaces. The valve requires a minimum of 10.5VDC in order to open
and when open, should draw no more than .48 amps.
Later model furnaces have an ON/OFF switch on the wire to the gas
valve. This replaces the manual shut-off that was used on earlier
model furnaces. You can now electrically shut off the gas to the valve
with this switch before servicing the furnace.
When these valves become inoperative, it is typically one or both of
the coils that fail. In order to determine which coil is at fault, you
need to conduct a continuity test on both leads of each coil. The
resistance on a good coil will be 30-50 ohms. If the resistance is not
in this range the coil is defective and must be replaced.
The coils on this valve are wired in parallel. Therefore, when
replacing the wires on these coils, it is important that they be
attached per the diagram. The red 12VDC supply wires must be
attached to terminals 1 and 4 and the ground wires must be
attached to terminal 2 and 3. If the coils are mistakenly wired in
series and there is a marginal supply voltage, there will be a voltage
drop from coil to coil and the valve will not open.
The burner head, electrode and gas valve on the late model 79 series
furnace are individually accessible. However, to service these same
components on the late model 85 and 89 series, remove the
complete assembly.
The different models and/or BTU ranges of furnaces use different
burner heads. These burners differ by the size of the top gas port
holes or the deflector that runs through the throat of the burner. If
the wrong one is used, it may cause an ignition, sooting or flame
sense problem.
When an electrode assembly is installed on a furnace, they will
already be in a fixed and predetermined position above the burner.
The only adjustment that you may need to do is on the sparking and
ground electrode points. This gap should be 1/8˝. However, when the
porcelain on an electrode assembly becomes cracked, it will not
function properly and will have to be replaced. When doing so, use
the proper electrode assembly for the model of furnace being
serviced.
There are only two versions of the solenoid valve available for the
models of furnaces noted above. These two valves are identical
except for the gas inlet porting on them (side or front). As stated
earlier in this manual though, the coils are what usually breakdown
but they are easily replaceable.
The different models and/or BTU ranges of furnaces use different
burner heads. These burners differ by the size of the top gas port
holes or the deflector that runs through the throat of the burner. If
the wrong one is used, it may cause an ignition, sooting or flame
sense problem.
Local Sense
Electrode
25
1/4"
1/8"
Remote Sense
Electrode

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