Technibel MCAV77R5VAA - Air Conditioner Operates, but Abnormalities Are Observed

8-4.Air conditioner operates, but abnormalities are observed.
8-4-1.Operation does not switch from HEAT to COOL (or COOL to HEAT).
•
Indoor PCB Ass'y is defective.
•
Check voltage between terminals
No. 1(+) and No. 3 at the terminal
plate. (DC 24V)
No voltage appears.
Outdoor PCB Ass'y is defective.
OK
•
Remote control unit may be defective.
•
Measure resistance of 4–way valve's
winding.
Receiver in lamp Ass'y may be
defective.
COOL ➞ HEAT
•
Check voltage between terminals
No. 1(+) and No. 3 at the terminal
plate. (0V)
HEAT ➞ COOL
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