50
C.
Drive motor works in forward mode but does
not reverse, blower motor runs...
1. If computer dot (second one [1] from left) does not come on, check program to see if set for reverse.
2. If set for reverse, replace computer.
3. Check for voltage across the coil of the reversing contactor located in the rear panel box. The contactor
according to your diagram is CR3, also the markings on the coil are A1 and A2.
If there is voltage, replace the coil or the complete contactor.
If there is no voltage, check for voltage across the two (2) BS1 terminals on the arc suppressor (A.S.)
board.
If there is voltage across the two (2) BS1 terminals and no voltage across the coil of the reversing contactor
(A1 and A2), the problem is bad wire(s) or termination(s) between BS1 and the contactor coil.
4. If there is no voltage between the two (2) BS1 terminals on the arc suppressor (A.S.) board, check for
voltage across the two (2) AS1 terminals on the board.
If there is no voltage across the two (2) AS1 terminals and no voltage across the two (2) BS1 terminals,
replace the arc suppressor (A.S.) board.
If there is no voltage across the two (2) AS1 terminals, the problem is bad wire(s) or termination(s)
between the arc suppressor (A.S.) board and the computer 15-pin connector no. 8, or a faulty computer.
D. Blower motor does not operate, drive motor runs...
1. Check for voltage across terminals A1 and A2 of the impellor contactor. This is the single contactor in the
rear control box.
If voltage is present check for voltage across the blower motor. If there is voltage at the blower motor
replace the motor.
If there is no voltage at the blower motor, problem is bad wire(s) or termination(s) between the contactor
and the motor.
2. If there is no voltage present at A1 and A2 of the contactor, check for voltage across the two (2) BS3
terminals of the arc suppressor (A.S.) board.
If there is voltage present at the two (2) BS3 terminals, problem is bad wire(s) or termination(s) between
the two (2) BS3 terminals and the coil (A1 and A2) terminals.
If there is no voltage across the two (2) BS3 terminals, check for voltage across the two (2) AS3 terminals.
If there is voltage across the two (2) AS3 terminals and there is no voltage between the two (2) BS3
terminals, replace the arc suppressor (A.S.) board.
3. If there is no voltage across the two (2) AS3 terminals, problem is bad wire(s) or termination(s) between
the two (2) AS3 terminals and the computer board 15-pin connector no. 5, or faulty computer.
Summary of Contents for AD-758
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