M2 MC2125PALS Service Manual - page 48

49

Diagnostics

10-3) If defrost function

Is F, R defrosting sensor by 

self-diagnosis normal?

Start

Exchange and troubleshoot the

corresponding sensor.

See Ref. 3: ‘Check load’ in the manual.

Make decision on the basis of ref. 4 and

6 in the manual.

See test function in the manual.

Recheck the corresponding sensor for 

an error if it fails in return.

See ‘Load Drive Circuit section’ and

Ref. 2: How to check failure of relay.

Is F, R Room defrosting heater normal?

Check temp. fuse, 

breaking of heater wire, contact of 

wire and so on.

Is temp. of the defrosting 

sensor below 23

℉

?

Run forced operation for a 

specified period.

Repair the connection terminal.

Perform forced defrosting for F and 

R room at a time.

Normal

Check temp. fuse, breaking of heater wire,

contact of wire, and so on.

Exchange or troubleshoot the failure relay or

exchange PCB ass’y.

Is power applied to the 

respective defrosting heaters?

Does the system 

return to cooling operation after heating 

for a specified period of time?

Recheck the connection 

terminal in Main PCB

NO

NO

YES

YES

NO

YES

NO

NO

NO

YES

YES

YES

If temp. of F, R defrosting sensor by the

working of heater are over 10

℃, 

17

℃

Reference