Carrier 538FEQ009RBGA, Service Manual

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4. Diagnosis for anti--high temperature, overload protection (AP1 below is control board of the outdoor unit).
Main detection points:
S If the outdoor ambient temperature is in the normal range
S If the indoor and outdoor fan is running normal
S Are the units clear of dirt and debris?
Malfunction diagnosis process:
1. Check if fan terminal
OFAN is connected well
2. Test if resistance value
of any two terminals is less
than 1k with ohmic meter
Do the indoor and outdoor
fan work?
After the unit
de-energized for 20min
Replace
control board
AP1
Outdoor unit coils clean?
Clean coils
Replace
outdoor fan
Y
Replace fan
capacitor C1
High temperature,
overload protection
Above operating envelope
If the outdoor ambient temperature is
higher than 127 ºF?
No
No
Y
No
End
Yes
Yes
Yes
Fig. 40 – Troubleshooting