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Problem Possible Cause Action
Room
temperature
uneven
(Heating cycle)
Heat anticipator (resistor) shorted
(on applicable models)
Disconnect power to unit. Remove resistor
from t-stat bulb block. Plus in unit & allow to
operate. Feel resistor for heat. If not heat,
replace resistor
Wide differential - partial loss of
t-stat bulb charge
Replace t-stat & check
Incorrect wiring
Refer to appropriate wiring diagram. Resistor
is energized during “ON” cycle of compressor
or fan.
Defective thermistor or control board Replace thermistor or electronic control board
Problem Possible Cause Action
Unit will not
defrost
Incorrect wiring Refer to appropriate wiring diagram
Defrost control out of calibration
(applicable models)
If outside coil temperature is 25°F or below,
& preselected time limit has elapsed, replace
defrost control
Defrost control contacts stuck
If contacts remain closed between terminals
“2” & “3” of the defrost control after
preselected time interval has passed, replace
control
Defrost control bulb removed from
or not making good coil contact
Reinstall & be assured that good bulb to coil
contact is made
Outdoor coil thermistor Replace thermistor or electronic control board
Problem Possible Cause Action
Does not heat
adequately
Dirty lter Clean as recommended in Owner’s Manual
Unit undersized
Check heat rise across coil. If unit operates
ef ciently, check if insulation can be added
to attic or walls. If insulation is adequate,
recommend additional unit or larger one
Outdoor t-stat open (applicable
models)
T-stat should close at 38°F. Check continuity
of control. If temperature is below 38°F,
replace control
Heater hi-limit control cycling on &
off
Check for adequate fan air across heater.
Check control for open at 160°F & close at
150°F
Shorted supplementary heater Ohmmeter check, approx. 32-35 ohms
Incorrect wiring Check applicable wiring diagram
Defective thermistor or electronic
control board
Replace thermistor or electronic control board
HEAT PUMP TROUBLESHOOTING