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NOTE: If applied to two-speed unit, do not select continuous fan
as high since LO speed cooling will also run at HIGH airflow and
insufficient dehumidification may result.
Step 13—Troubleshooting PCB
Use Fig. 25 and 26 and Tables 7 and 8 as guides in troubleshooting
PCB unless otherwise noted.
IF FAN WILL NOT TURN ON FROM THERMOSTAT:
If There Is No High Voltage To Motor:
1. Check connection of 12-pin plug from heaters to receptacle.
This supplies power to transformer and motor. Be sure plug is
connected properly.
2. Check power leads L1 and L2. If these are not receiving
power, system cannot function.
If Motor Has High Voltage Applied To It:
1. Check low-voltage transformer leads (red and brown). Be sure
they are wired to correct locations. (See Fig. 24 and 26.)
2. Check low-voltage fuse shown in Fig. 24. If fuse is blown,
replace it. The transformer cannot supply power to board with
fuse blown or loose. If fuse blows when unit has power
applied to it, the system most likely has 1 of the following
problems:
a. Check control circuit for a short or miswiring problem.
b. The maximum load on transformer is 40 VA. If load on
transformer is excessive, the low-voltage 5-amp fuse will
blow to protect transformer. If load exceeds VA rating of
transformer, a larger VA rated transformer needs to be
installed.
c. Check sequencers for excessive current draw.
d. Check wiring of heaters. If a heater is miswired, fuse may
blow. If a heater is miswired, correct miswiring.
3. Check yellow and black wire connections on primary side of
transformer. If they are not connected properly, low-voltage
transformer cannot supply 24-v signal to energize fan motor.
If transformer is receiving correct primary voltage but is not
putting out correct secondary voltage, transformer needs to be
replaced.
IF ELECTRIC HEAT STAGES WILL NOT TURN ON BUT
FAN WILL TURN ON:
1. Check wiring of sequencers. Pay particular attention to high-
and low-voltage wiring of sequencers.
2. Check plug wiring to make sure that it is wired correctly.
3. Check voltage to sequencer. Sequencer number 1 receives a
24-vac signal. If it is receiving correct voltage, check to see if
sequencer is closing. If sequencer is not closing but is
receiving correct voltage, replace sequencer. If sequencer is
closing, check high-voltage wiring as discussed in items 1 and
2.
If Traces Are Overheated on Back of PCB:
Usually whenever there is a trace blown on PCB, it means either
there has been a high-voltage short or high voltage has been
applied to low-voltage circuit. This can be prevented by making
sure PCB is wired correctly before fan coil has power applied to it.
IF PCB FUSE KEEPS BLOWING:
When low-voltage fuse blows, it means transformer would have
blown if fuse had not been in circuit to protect it. The fuse usually
blows when there is a high current drawn on transformer, high
voltage applied to low-voltage circuit, or a direct secondary short.
When there is a high current drawn on transformer, it is most likely
because transformer has been shorted or system is trying to draw
more va than transformer rating allows. When fuse blows because
of high voltage, the system has mixed high- and low-voltage
signals.
1. Check transformer and thermostat wiring. (See Fig. 24 and
26.) Be sure transformer is not shorting out because thermostat
wires are miswired.
2. Check wiring of sequencers. (See Fig. 24 and 26.) Be sure
low-voltage and high-voltage wiring are connected to proper
sequencers.
3. Check VA draw on transformer. If VA draw is more than VA
rating of transformer, fuse will blow. If this is the case, replace
transformer with one that has a higher VA rating.
Step 14—Troubleshooting ICM2 Fan Motor
IF MOTOR DOES NOT RUN:
1. With power turned off, check all plugs and receptacles on
circuit board and at motor for any deformation that may cause
a bad connection. Be sure all plugs are placed fully seated.
2. Verify that there is approximately 230v.
3. Verify that there is a low-voltage control signal to motor. The
motor receives its control signals through the 12-pin motor
plug PL1. The voltage output of each pin in plug will be
different for each mode of operation. Table 9 lists circuit
board screw terminals that have 24 vac present (powered by
thermostat) and lists voltage that is present at each pin of
12-pin plug for each operating mode. Tests should be taken
between points listed and common (C screw terminal). If all
values of any 1 of operating modes check OK and motor fails
to run, then motor is defective and should be replaced.
IF MOTOR DOES NOT RUN SMOOTHLY:
First verify that the cause is not an out-of-balance or damaged
blower wheel. If it is not blower wheel, motor is defective and
should be replaced.
IF MOTOR SHAFT DOES NOT ROTATE SMOOTHLY:
When manually turning shaft of ICM, the shaft does not rotate
smoothly. The shaft has steps during rotation referred to as motor
cogging. The cogging is caused by permanent magnets passing
each pole of motor. However, shaft should not require excessive
force to turn. If shaft is VERY difficult to turn, motor control or
bearings have failed and motor must be replaced.
IF MOTOR DOES NOT STOP RUNNING
1. Check for good ground between motor ground lead and
transformer common lead.
2. If motor continues to run, remove all thermostat wires. If
motor stops, check thermostat wiring to thermostat or outdoor
unit for shorts or miswire.
Step 15—Condensed Version of Troubleshooting FK4C,
FV4A, and 40FKA Motor and Controls
This section provides a quick summary of how to troubleshoot the
FK4C, FV4A, and 40FKA. If more information is needed, refer to
appropriate sections of this service manual.
+ MOTOR
- If motor is hard to turn manually, replace motor.
- If motor does not run, check the components listed below
according to their instructions.
- If motor runs in some operation modes and not in others,
check for a good ground connection between motor ground lead
and circuit board screw marked "ground screw" and check the
room thermostat and wiring harness according to instructions
listed below.
33
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Table of Contents
Troubleshooting
