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0920 IH-8771
TROUBLESHOOTING CONTINUED
OPERATING ISSUE
CAUSES
RECOMMENDATIONS
Unit displays AL and
audio alarm is sounding
during start up or while
operating.
Microprocessor board has detected
high pressure. The high pressure
switch is tripped.
High pressure is normally caused by
reduced condenser air flow.
Check for restriction in ducting.
Check for condenser air system
ventilation.
Check condenser motors and/or blowers
for proper operation.
High pressure is a manual reset type.
To reset, press the button labeled HP
reset located in the condenser make-up
air inlet on the back of A/C unit (it will
click when resetting).
System is on and
display is showing ON
but unit is not supplying
conditioned air.
System is in timeout (F or C is
flashing), control is set above room
temperature or control is adjusted
out of operating parameters or not
in the correct operational mode.
Wait two minutes, and recheck display.
Power is supplied but
control is blank.
Low voltage circuit is not engaged.
Check source power breaker and verify
incoming power to connector. Call Uline
Customer Service at 1-800-295-5510 for
assistance.
System trips breaker on
startup.
Incoming power is incorrect, breaker
is undersized or faulty, and/or power
cable is too long and/or undersized.
Verify the circuit and power cable is
within the system's specifications, consult
with a licensed electrician or call Uline
Customer Service at 1-800-295-5510
for assistance.
Display shows 32 and
unit will not turn on
cooling.
No connection of temperature
sensor to Microprocessor.
Temperature Sensor malfunction.
Call Uline Customer Service at
1-800-295-5510 for assistance.
Chatter or hum is heard
from the control box
while the system is
operating.
Incoming source power is poor or
low voltage component is faulty.
Check for proper incoming voltage;
remove excess or undersized power
cable. Call Uline Customer Service at
1-800-295-5510 for assistance.
Supply air flow is limited,
and/or water is dripping
from the front of the
system.
Supply or return air is blocked or
restricted, and/or the evaporator coil
is freezing.
Verify that supply and return air are not
blocked and duct work is installed to
specification, remove or add duct as
needed, check air filter for blockage.
