A.O. Smith 120 trough 500 - Manual (Page 32)

BTR TANK TYPE HEATERS
SERVICE HANDBOOK
A.O. Smith Water Products Service Handbook
Irving, Texas ©2000 Training Department
31
TROUBLESHOOTING THE EFFIKAL STYLE DAMPER (continued)
Condition:
Thermostat closed, damper is open fully
STEP A3 TEST FOR 24VAC BETWEEN BLACK AND YELLOW
IF THEN
24VAC is present This is correct – continue to Step 11
24VAC is not present • See Step 9
• Check the harness plug connecting ----
• Check that cam on shaft rotates with
shaft
• Replace the damper board