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45
Service Manual
3 Troubleshooting (continued)
Gas valve adjustment procedure
If adjustment of the gas valve is deemed necessary, use the
following procedures: (Note: The procedures below are
model specific.)
Figure 3-3 Gas Valve Adjustment: Model 501
Model 501
Locate the throttle adjustment screw on top of the gas valve,
see FIG. 3-3. Using a screwdriver, turn the screw a 1/4 turn
counterclockwise to increase CO
2
levels or a 1/4 turn
clockwise to decrease CO
2
levels. After one adjustment on
the valve, follow the Combustion Analysis Procedure on
page 44 of this manual to measure the combustion.
If combustion is still not within the specified range, repeat
the procedure. This procedure SHOULD NOT be
performed more than four (4) times. If after four (4)
adjustments and the combustion is still not within the
specified range, revisit the possible causes in Table 3-5 on
page 44 or replace the gas valve.
CAUTION
Under normal operating conditions this
valve should not need adjusting.
Model 400
Models 601 - 801
Locate the throttle adjustment screw on top of the gas valve,
see FIG. 3-4. Using an Allen wrench, turn the screw a 1/4 turn
counterclockwise to increase CO
2
levels or a 1/4 turn
clockwise to decrease CO
2
levels. After one adjustment on
the valve, follow the Combustion Analysis Procedure on page
44 of this manual to measure the combustion.
If combustion is still not within the specified range, repeat the
procedure. This procedure SHOULD NOT be performed
more than four (4) times. If after four (4) adjustments and
the combustion is still not within the specified range, revisit
the possible causes in Table 3-5 on page 44 or replace the gas
valve.
THROTTLE
ADJUSTMENT
SCREW
(REMOVE BLUE CAP)
Figure 3-4 Gas Valve Adjustment: Models 601 - 801
Locate the throttle adjustment screw on the top of the gas
valve, see FIG. 3-2. Using a screwdriver, turn the screw 1/8
turn counterclockwise to increase CO
2
levels or 1/8 turn
clockwise to decrease CO
2
levels. After one adjustment on
the valve, follow the Combustion Analysis Procedure on
page 44 of this manual to measure the combustion.
If combustion is still not within the specified range, repeat
the procedure. This procedure SHOULD NOT be
performed more than four (4) times. If after four (4)
adjustments and the combustion is still not within the
specified range, revisit the possible causes in Table 3-5 on
page 44 or replace the gas valve.
THROTTLE ADJUSTMENT
SCREW
Figure 3-2 Gas Valve Adjustment: Model 400