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4. Blower motor does not operate, drive motor runs.
A. 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 blow 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 or a bad impellor contactor.
B. If there is no voltage present at A1 and A2 of the contactor, check for voltage across the two BS3
terminals of the arc suppressor board.
If there is voltage present at the two BS3 terminals, problem is bad wire(s) or termination(s) between
the two BS3 terminals and the coil (A1 and A2) terminals.
If there is no voltage across the two BS3 terminals, check for voltage across the two AS3 terminals.
If there is voltage across the two AS3 terminals and there is no voltage between the two BS3 terminals,
replace the arc suppressor board.
C. If there is no voltage across the two AS3 terminals, problem is bad wire(s) or termination(s) between
the two AS3 terminals and the computer board 15 pin connector no. 5, or faulty computer.
5. "No Heat" drive & blower motors run, display reads normal (Gas Models).
A. Check for voltage across terminal block nos. 3 and 7.
If no voltage is present, problem is bad wire or broken terminal from terminal block no. 3 to MP
harness connector pin 4.
B. If voltage is present, check for voltage across terminal block nos. 4 and 7.
If no voltage is present, problem is bad wire or broken terminal from terminal block 3 to tumbler
hi-limit switch and back to terminal block no. 4, or faulty tumbler hi-limit switch.
C. If voltage is present, check for voltage across DSI module "TH" and "GND".
If no voltage is present, check voltage through the sail switch and burner hi-limit harness against
ground. Also check for voltage at the terminals of both components. If voltage is not passing
through any one of the two components, replace that component.
D. If voltage is present, refer to DSI technical manual (P/N 450119), or if equipped with ADC style DSI
module refer to technical manual (P/N 450142).