Power at end of limit string when it shouldn’t be. 

• Control, vent damper, or damper harness is defective. With Error 56 present, and
no call for heat, unplug damper harness from control and check for 24VAC between termminal P6-5 on control (see Figure 9.2 for location) and ground. If voltage is present, replace control. If not, inspect the damper harness for shorts or miswired con- nections. If no harness defect is found, replace vent damper.