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A. No display condition...
1. Check main fuses or circuit breaker.
2. Check blower motor overload, if tripped, reset.
3. Check fuse 1 or fuse 2 and if either are blown, replace.
4. Across terminal block nos. 6 and 8 you should be getting your 208V or 240V.
If no voltage is present at 6 and 8, double check steps 1 and 2 and also check wires and terminations at
these points.
5. Take voltage reading across the microprocessor 15-pin connector nos. 7 and 13.
If there is voltage, replace the computer.
If there is no voltage, there is a bad wire(s) or termination(s) between terminal block nos. 6 and 8 and
microprocessor 15-pin connector nos. 7 and 13.
NOTE: In this next section ALL voltage checks must be done in the operating mode with the
appropriate microprocessor dot on!! Also appropriate light emitting diode (L.E.D.) output
light on!!
NOTE: In this next section when checking for voltage you are looking for 24 VAC unless otherwise
specified.
B. Drive motor reverses but does not go forward, blower motor runs...
1. If computer dot (first dot on the left) does not come on, replace the computer.
2. Check for voltage across the coil markings A1 and A2 of the forward contactor located in the rear panel
box. The contactor according to your diagram is marked CR2.
If voltage is present, there is a bad wire(s) or termination(s) between BS2 and contactor coil (CR2).
3. If there is no voltage between the two (2) BS2 terminals and no voltage across the two (2) BS2 terminals,
replace the arc suppressor (A.S.) board.
If there is voltage across the two (2) AS2 terminals and no voltage across the two (2) BS2 terminals,
replace the arc suppressor (A.S.) board.
If there is no voltage across the two (2) AS2 terminals on the arc suppressor (A.S.) board, the problem is
bad wire(s) or termination(s) between the AS2 board and the 15-pin computer connector no. 3, or faulty
computer.