Damper Motor Replacement & Adjustment - Cambridge Engineering S Series Technical Manual

TROUBLESHOOTING INSTRUCTIONS
DAMPER MOTOR REPLACEMENT & ADJUSTMENT
1. Before reinstalling the damper motor into the heater
assembly, remove the black plastic weather cover
from the damper motor by removing the screw that
secures the cover to the damper assembly using
either a flat tip screw driver or a ¼" nut driver. It
may be necessary to twist the cover slightly to dis-
engage it from its mounting to the end of the motor
after the screw is removed.
2. Verify the damper motor is in the CLOSED posi-
tion (Drive tube is retracted with a minimum of
1/4" gap between the drive tube and the body of the
damper assembly).
3. Verify the inner cam has fully engaged the lower
limit switch plunger and the lower limit switch
(next to the body of the damper motor) shows con-
tinuity between the common (C) terminal and the
normally open (NO) terminal.
mCAUTION:
If the lower limit switch does not indicate con-
tinuity, the damper motor must be driven to the
fully CLOSED position BEFORE connecting the
damper linkage tube to drive tube of damper motor
assembly.
IMPORTANT
If the drive tube bottoms out against the damper
motor housing, damage to the PC board or trip-
ping of the onboard fuse may result. If the fuse trips,
place the blower service switch in the OFF position
for 15 seconds to allow fuse to reset. Proceed with
steps 4 through 10 PRIOR to connecting the damper
motor to the linkage tube.
4. Verify the cam location on the upper cam is set just
short of the four o'clock position with respect to
the switch plunger being the twelve o'clock refer-
ence position. If it is beyond the four o'clock posi-
tion, use a deep well 1/2" hex socket or nut driver
and manually rotate the cam counterclockwise a
few clicks, as required, to obtain the correct starting
position. (Refer to Figure 1.)
Cambridge Engineering, Inc.
5. Verify the heater disconnect switch is turned OFF
and the service switches are in the OFF position.
6. Connect the wires to the terminals as shown in
Figure 2 and reinstall the cover.
7. Remove the push-in plug (located in the weather
cover) to have access to the upper cam adjusting
nut.
8. Connect the motor pivot to the damper motor sup-
port bracket using the 3/8" diameter clevis pin.
Do not connect the damper linkage tube at this time.
9. Remove the wire from the "G" terminal of the ter-
minal block. (This is to avoid a "Call-for-Fan"
signal from the remote control station during the
next two steps).
54
Figure 1
Figure 2
IMPORTANT
S-Series Technical Manual