Carrier AirStream 42WKN08-36 Installation, Operation And Maintenance Instructions page 59

PROBLEM
Two LEDs Flashing
(Microprocessor Units Only)
Unit Will Not Operate
Fans Will Not Run
No Cooling
Condensate High Level
(Microprocessor Units: LEDs
Will Flash)
LEGEND
LED — Light-Emitting Diode
PCB — Printed Circuit Board
Table 7 — Troubleshooting
POSSIBLE CAUSE
Faulty float switch
(Connected to microprocessor terminals 'T4')
Fan thermal trip
(Connected to microprocessor terminals 'T4')
Freeze stat alarm
(Connected to microprocessor terminals 'T4')
Return air sensor failure
(Connected to microprocessor terminals 'T1')
No power mains power
No 24-v control circuit power
Control circuit disabled by unit protection device
Infrared receiver failure
(microprocessor units only)
Transmitter failure
(microprocessor units only)
Microprocessor failure
(microprocessor units only)
Loose wire
Faulty fan capacitor
Faulty fan motor
Fan thermal trip
Faulty PCB
Incorrect MODE setting
(microprocessor units only)
Set point too high
Dirty or blocked air filter
High condensate level trip
Sensor failure
(microprocessor units only)
Faulty valve actuator
(chilled water units only)
Maximum pump lift exceeded
Blocked/kinked condensate pipe
Condensate pump blocked or failed
Coil freeze up
See Condensate High Level section in this table.
See Fans Will Not Run section in this table.
—
After checking the above, 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.
Check power supply to the unit. For microprocessor units, check
power to the microprocessor and check the on-board
microprocessor fuse.
Check the 24-v feed from the control transformer. If not present,
check transformer windings and replace if necessary.
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 schematic to
identify these devices and investigate accordingly.
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.
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.
The microprocessor is the least likely component to be at fault.
Investigate all other possibilities in every section of this
troubleshooting guide first. Replace the microprocessor only after
all other avenues of investigation are exhausted.
Check all fan wire connections. Use unit's electrical schematic to
verify that fan is wired correctly.
Check fan capacitors and replace if necessary.
Check fan motor protector for open circuit, and replace if
necessary.
Motor temperature limits exceeded. Check fan motor protector
for open circuit, and replace if necessary.
On electro-mechanical units check for a signal at "G" terminal.
On microprocessor units check for steady green light on display
panel.
Check that the transmitter MODE is set to Cooling or Auto Mode.
Check the set point on the transmitter or wall-mounted
thermostat and adjust if necessary.
Check filter condition.
Drain the condensate tray and investigate. See Condensate High
Level section.
If any of the sensors are faulty, the microprocessor will disable
the cooling operation. (See the "Self Diagnostics" section on
page 10.)
Check cooling signal present at actuator. Check actuator by
manually opening the valve. Replace actuator if necessary.
Check that the condensate pump head is no greater than 30 in.
(See page 42 of this manual for installation guide.)
See Water Leaking from Unit section in this table.
See Water Leaking from Unit section in this table.
A coil freeze condition may have caused excessive condensate
to collect in the drip tray.
59
POSSIBLE SOLUTION