Checking and resetting cams

1. Remove the top cover so that you can gain access to the tops of the cams (Figure 2).

2. Make sure the shaft of the mod motor is rotated to its position for a fully closed damper.

3. Check positions of the target lobes of the cams. The cams have click stops that hold them in position. Repositioning a cam does not turn the drive shaft of the mod motor.

4. You may be able to rotate the cams with your fingers. Otherwise insert the blade of a screwdriver in the slots of the cam (Figure 9) and rotate them.

   
   Figure 9. Using screwdriver to position cams.

5. In order to make sure the cams are positioned properly you may need to rotate them until you can see their target lobes (indicated by yellow dots in Figure 10) and then reset them to their proper positions. NOTE: The yellow dots are only shown in Figure 10. There are no dots on the actual lobes.

6. You can also use the blade of a small screwdriver to press on the actuating arms of the switches to determine whether they are actuated. All switches except the blue low-fire switch should not be actuated while the damper is closed. Thus you should hear a distinct click if you press on their actuating arms.

7. Because the blue low-fire switch should be actuated or held closed by the cam when the damper is closed, you should not be able to move its actuating arm. Note that it is shown with its arm in the actuated position in Figure 10.

8. Make sure the target lobes of the two cams are rotated to the positions shown relative to the actuating arms of the two switches as shown in Figure 10. The U-shaped ends of the switch arms should rest on the cams as shown in Figure 10.

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