63
HEAT / COOL ONLY ROOM AIR CONDITIONERS: TROUBLESHOOTING TIPS
Possible Solution
Possible Solution
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Room temperature
uneven
(Heating cycle)
Check error codes. Replace as needed.
Bad indoor ambient thermistor
Set at higher fan speed.
Fan speed too low
Close doors, windows, etc.
Opened door, windows, etc.
Enable ATSF
ATSF (room air sampling feature) disabled
Possible Solution
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Unit will not defrost
(Heat pump
only models)
Replace thermistor.
Bad outdoor coil thermistor
• On heat pumps with electric heat: no action needed
• On model YSM10: do not operate below 32°F/ 0°C
• If outdoor air temp is higher than freezing, check
reversing valve, electric coil, outdoor thermistor,
refrigerant circuits, etc.
• For proper operation: correct as needed
Temperature below 32°F/ 0°C
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Does not heat
adequately
Exhaust or fresh air door open
Check if operating properly. Instruct customer on
proper use of control
Dirty fi
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Unit undersized
Check heat rise across coil. If unit operates
effi ciently, check if insulation can be added
to attic or walls. If insulation is adequate,
recommend additional unit or larger one
Outdoor coil thermistor or electronic control
board defective
Heater hi-limit control cycling on & off
Check for adequate fan air across heater. Check
for open hi-limit control.
Check alarms (error codes). Replace thermistor
or electronic control board.
Shorted or open supplementary heater
Do ohmmeter check.
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