37
Table 6 — Troubleshooting
LEGEND
PROBLEM
POSSIBLE CAUSE
POSSIBLE SOLUTION
Red Alarm LED Flashing at 1-Second
Intervals (Microprocessor Units Only)
Faulty float switch
See Condensate High Level section.
Fan trip
See Fans Will Not Run section.
Indoor coil sensor failure
(Connected to microprocessor termi-
nals ‘T3’)
After checking the above, use the unit wiring schematic to iso-
late the indoor coil sensor and measure the resistance. Sensor
is 50K at 72 F type. Check and replace if necessary.
Red Alarm LED Flashing at 5-Second
Intervals (Microprocessor Units Only)
Return air sensor failure
(Connected to microprocessor termi-
nals ‘T1’)
Use the unit wiring schematic to isolate the return air sensor
and measure the resistance. Sensor is 50K at 72 F type.
Check and replace if necessary.
Both Yellow Heat and Cool LEDs
Flashing (Microprocessor Units Only)
Control Board (PCB) battery failure
Check battery and replace if necessary. See the Microproces-
sor PCB Battery section.
Unit Will Not Operate
No power mains power
Check power supply to the unit. For microprocessor units,
check power to the microprocessor and check the on-board
microprocessor fuse.
No 24-v control circuit power
Check the 24-v feed from the control transformer. If not present,
check transformer windings and replace if necessary.
Control circuit disabled by unit
protection device
In some models, particularly electro-mechanical units, some
protection devices (such as freezestats, fan trips, etc.) are
wired in line with the 24-v control circuit feed to cause the unit
to shut down in an alarm condition. Use the unit’s wiring sche-
matic to identify these devices and investigate accordingly.
Infrared receiver failure
(microprocessor units only)
If audible bleep is heard on signal transmission from transmitter
and the green LED is lit or flashing, receiver is OK. If there are
no lit LEDs and the unit will not respond to the transmitter,
press the on/off button on the fascia display panel. If the unit
responds to the on/off button receiver is OK. Check transmitter.
Transmitter failure
(microprocessor units only)
Try new batteries first, if receiver bleeps on transmitting signal,
transmitter is OK. If no response press on/off button on unit fas-
cia. If the unit responds to the on/off button transmitter is faulty.
Microprocessor failure
(microprocessor units only)
The microprocessor is the least likely component to be at fault.
Investigate all other possibilities in every section of this trouble-
shooting guide first. Replace the microprocessor only after all
other avenues of investigation are exhausted.
Fans Will Not Run
Loose wire
Check all fan wire connections. Use unit’s electrical schematic
to verify that fan is wired correctly.
Faulty fan capacitor
Check fan capacitors and replace if necessary.
Faulty fan motor
Check fan motor protector for open circuit, and replace if
necessary.
Faulty PCB
On electro-mechanical units check for a signal at “G” terminal.
On microprocessor units check for steady green light on display
panel.
No Cooling
Incorrect MODE setting
(microprocessor units only)
Check that the transmitter MODE is set to Cooling or Auto
Mode.
Set point too high
Check the set point on the transmitter or wall-mounted thermo-
stat and adjust if necessary.
Compressor protection delay
(microprocessor units only)
Check that the green on/off LED is not flashing. If it is flashing,
wait for ten minutes then re-check if cooling is operating.
Dirty or blocked air filter
See Coil Freeze section.
High condensate level trip
Drain the condensate tray and investigate. See Condensate
High Level section.
Indoor coil temperature too low
Check refrigerant charge by measuring operating pressures.
Check filter condition. (See page 35 for filter removal and
cleaning instructions.)
Sensor failure
(microprocessor units only)
If any of the sensors are faulty, the microprocessor will disable
the cooling operation. (See the Self Diagnostics section.)
Faulty valve actuator
Check cooling signal present at actuator. Check actuator by
manually opening the valve. Replace actuator if necessary.
Condensate High Level
(Microprocessor Units: Red Alarm LED
Will Flash at One Second Intervals)
Maximum pump lift exceeded
Check that the condensate pump head is no greater than
30 in. (See page 19 of this manual for installation guide.)
Blocked/kinked condensate pipe
See Water Leaking from Unit section.
Condensate pump blocked or failed
See Water Leaking from Unit section.
Coil freeze up
A coil freeze condition may have caused excessive condensate
to collect in the drip tray. See Coil Freeze section.
Coil Freeze
Cooling coil freeze protection thermo-
stat tripped
(Auto-reset when freeze cleared)
Freeze thermostat is normally closed, opens during freeze.
Where fitted, the thermostat will disable the cooling action
(sometimes the entire system) during coil freeze conditions.
Use the unit’s wiring schematic to investigate.
Dirty or blocked air filter
Clean/replace filters as necessary. (See page 35 for filter
removal and cleaning instructions.)
LED —
Light-Emitting Diode
PCB —
Printed Circuit Board
