Service Manual

13
1190281 board for ECM motors
A150020
Fig. 8 – FAST # 1173636 / 1177927 / 1190281 Defrost Control
Troubleshooting (FAST # 1173636 / 1177927
/ 1190281 )
If outdoor unit will not run:
1. Does the Y input has 24 volts from thermostat? If not,
check thermostat or wire. If yes proceed to #2
2. The Y spade terminal on the circuit board should
have 24 volts if Y input is energized. This output goes
through the pressure switches and to the contactor. If
24 volts is present on the Y spade terminal, and the
contactor is not closed, check voltage on contactor
coil. If no voltage is present, check for opened
pressure switch.
3. If voltage is present and contactor is open, contactor
may be defective. Replace contactor if necessary.
4. If contactor is closed and unit will still not run, check
wiring, capacitor and compressor
Defrost Speedup (FAST # 1173636
/ 1177927 / 1190281)
To test the defrost function on these units, speed up pins
are provided on the circuit board. To force a defrost cycle,
the defrost thermostat must be closed, or the defrost
thermostat pins must be jumpered. Follow the steps below
to force a defrost cycle:
1. Jumper the DFT input
2. Short the speed up pins. This speeds up the defrost
timer by a factor of 256. The longer the defrost
interval setting, the longer the pins must be shorted to
speed through the timing. For example, if interval is
90 min, the speed up will take (90/256)min x
(60seconds /minute)= 21 seconds max. This could be
shorter depending on how much time has elapsed
since the defrost thermostat closed.
3. Remove the short immediately when the unit shifts
into defrost. Failure to remove the short immediately
will result in a very short forced defrost cycle (the 10
minute timer will be sped through in 2 seconds)
4. When defrost begins, it will continue until the defrost
thermostat opens or 10 minutes has elapsed.
NOTE: The T1 terminal on the defrost board powers the
defrost timing function. This terminal must be energized
before any defrost function will occur.
If defrost thermostat is stuck closed:
Whether the unit is in heating or cooling mode, it will run a
defrost cycle for 10 minutes each time the compressor has
been energized for the selected time interval. The board will
terminate automatically after 10 minutes of defrost time
regardless of defrost thermostat position.
If defrost thermostat is stuck open:
The unit will not defrost
NOTE: Unit will remain in defrost until defrost thermostat
reopens at approximately 65_F coil temperature at liquid line
or remainder of defrost cycle time.
5. Turn off power to outdoor unit and reconnect
fan- motor lead to OF2 on control board after above
forced- defrost cycle.
If unit will not defrost:
1. Perform the speedup function as described above to
test the defrost function of the circuit board.
2. If the unit does not go into defrost after performing the
speed up, check for 24 volts on the T1 terminal. This
terminal powers the defrost circuit, and must be
energized before any defrost function can occur. The
T1 should be energized once the Y terminal is
energized and the pressure switches are closed.
Ensure the T1 wire is connected at the contactor, and
that 24 volts is present on the T1 spade terminal.
3. If all voltages are present and unit will still not run
defrost, remove thermostat pigtail harness from board
and perform checks directly on input pins with jumper
wires. The pigtail may have a bad connection or be
mis- wired.