A.O. Smith 120 trough 500 Service Handbook page 27

STEP 10
STEP 10. TEST DAMPER OUTPUT.
power through the yellow wire and power to the motor is interrupted.
clutch is disengaged and the damper opens. The damper proves it is open via an end
switch before power flows through the red wire from the PC board.
Place the red test probe on the solder joint of the red wire connection to the damper PC
board.
IF
The meter does not read 24 VAC and the
end switch is closed:
The meter reads 24 VAC
Note: The spring rotates the damper blade assembly to the open position. This closes an end
switch.
A.O. Smith Water Products
Irving, Texas ©2000
BTR TANK TYPE HEATERS
SERVICE HANDBOOK
TEST DAMPER OUTPUT
On a call for heat, the damper relays receives
THEN
• Replace the PC board
• Go to step 11.
26
Then, the motor
Service Handbook
Training Department