First Co EVBQ (Variable Speed) - Manual (Page 15)

PROCEDURE 11 – TROUBLESHOOTING ECM MOTOR AND CONTROLS
CAUTION: High voltage is always present at the motor. Disconnect power to the unit before removing or
replacing connectors or servicing motor. Wait at least 5 minutes after disconnecting power before opening
motor. Failure to follow this CAUTION could result in personal injury or product and property damage.
The ECM motor contains two parts: the control module and motor winding section. Do not assume the motor or module is
defective if it will not start. Go through the steps described below before replacing control module, Select Control Board or
entire motor.
A. If motor turns slowly:
1. Replace panel. Motor may appear to run slowly if access panel is removed.
2. It is normal operation to run noticeably slower if G terminal is energized without a call for heat or cooling.
B. If motor does not run:
1. Check for 24VAC at terminal R and C1. If no voltage is present, check the transformer.
2. Check all plugs and receptacles for any deformation, which could cause loose connections. Be sure plugs are fully
seated.
3. Verify that approximately 120VAC is present at the motor.
C. Check control signals:
Verify low voltage control signals to motor. The motor receives its control signals through the 16-pin wiring harness.
The combination of pins energized will determine the motor speed. See table 2 for pin number on 16-pin plug which
should have voltage when Select Control Board screw terminals have 24VAC.
Thermostat
1. Remove all thermostat wires from Select Control board,
2. Jumper screw terminals on the select control board one at a time: R-G, R-Y1, and R-W1. (Note: R-W1 must be
jumpered for at least a minute to see if motor will run.) If motor runs in all cases, thermostat is miswired, config-
ured incorrectly or defective. If motor runs in some cases, but not others, continue to check wiring harness and
circuit board.
Wiring Harness
1. Shut off power to unit. Wait 5 minutes.
2. Remove 5-pin connector from motor.
3. Remove 16-pin connector from motor.
4. Replace 5- pin plug and turn power on.
5. Check for correct voltages on 16-pin connector with screw terminals jumpered. ( See table 2 for values.)
If signals check correctly and motor does not run, inspect wiring harness for loose pins or damaged plastic connec-
tors that could cause poor connections. If connections are good, either motor control module or motor is defective.
If proper signals are not present, check Select Control Board using procedure below:
16-pin Plug on Select Control Board
1. Unplug wiring harness from board.
2. Check for appropriate voltage on connector pins with Select Control Board terminals jumpered. See table
2 for values and example below.
If proper signals are not present, replace the Select Control Board. If signals are present at the board and not the
other end of the wiring harness, the wiring harness is defective.
TROUBLESHOOTING EXAMPLE:
Motor is not running on a call for cooling.
1. After performing checks in Thermostat section, follow steps 1 thru 5 in the Wiring Harness section. Then proceed
with the example.
2. With all thermostat wires removed from the Select Control board, place a jumper wire between R and Y2 low
voltage terminals on the Select Control board. If using a heat pump, then jumper R to O as well.
3. Check table 2 for pin number on the 16-pin connector associated with the Y signal. The correct pin is #14. The far
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