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 in this section

are model specific.)

Models 151 - 286

Locate the throttle adjustment screw on the side of the

venturi valve (FIG. 3-2). Using a screwdriver, turn the screw

a 1/4 turn clockwise to decrease CO

levels or a 1/4 turn

counterclockwise to increase CO

levels. After performing

one adjustment on the valve, follow the Combustion

Analysis Procedure on page 36 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 3H on page 36 or replace the gas

valve.

Figure 3-2 Gas Valve Adjustment: Models 151 - 286

Model 400

Locate the throttle adjustment screw on the top of the gas

valve, see FIG. 3-3. Using a screwdriver, turn the screw 1/8

turn counterclockwise to increase CO

levels or 1/8 turn

clockwise to decrease CO

levels. After one adjustment on

the valve, follow the Combustion Analysis Procedure on page

36 of this manual to measure the combustion.