57
Table 5 — Troubleshooting
LEGEND
PROBLEM
POSSIBLE CAUSE
POSSIBLE SOLUTION
Two LEDs Flashing
(Microprocessor Units Only)
Faulty float switch
(Connected to microprocessor termi-
nals ‘T4
’
)
See Condensate High Level section in this table.
Fan thermal trip
(Connected to microprocessor termi-
nals ‘T4
’
)
See Fans Will Not Run section in this table.
Freeze stat alarm
(Connected to microprocessor termi-
nals ‘T4
’
)
See Coil Freeze section in this table.
Return air sensor failure
(Connected to microprocessor termi-
nals ‘T1
’
)
After checking the above, use the unit wiring schematic to iso-
late the return air sensor and measure the resistance. Sensor
is 50K at 72°F type. Check and replace if necessary.
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 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 no response, press on/off button on
unit fascia. 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.
Fan thermal trip
Motor temperature limits exceeded. 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
(electro-mechanical DX units only)
Wait for 10 minutes, then re-check to determine if cooling is
operating.
Dirty or blocked air filter
See Coil Freeze section in this table.
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 55 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 on
page 7.)
Faulty valve actuator
(chilled water units only)
Check cooling signal present at actuator. Check actuator by
manually opening the valve. Replace actuator if necessary.
Condensate High Level
(Microprocessor Units: LEDs Will
Flash)
Maximum pump lift exceeded
Check that the condensate pump head is no greater than 30-in.
(See page 39 of this manual for installation guide.)
Blocked/kinked condensate pipe
See Water Leaking from Unit section in this table.
Condensate pump blocked or failed
See Water Leaking from Unit section in this table.
Coil freeze up
A coil freeze condition may have caused excessive condensate
to collect in the drip tray. See Coil Freeze section in this table.
LED —
Light-Emitting Diode
PCB —
Printed Circuit Board
