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SM830063
Service Procedures
10. Malfunction due to Noise
Since communication control is performed by pulse signals, the unit is susceptible to external noise. The circuitry has
been designed in consideration of external noise and troubles should not occur in ordinary use. However, depending on
the installation conditions, there may be trouble caused by the noise.
High-frequency noise, etc. is superimposed on the signal wire and the signal pulses come abnormal, resulting in mal-
function.
Location easily subject to noise
Symptom
Remedy
1. Area with strong radio waves in the
1. Stops during operation.
Treat the signal wire so that it will
vicinity of a broadcasting station.
2. Liquid crystal display flickers.
not be influenced by noise.
2. In the vicinity of a radio station.
↓
3. Location near a high-frequency sewing
• Place the signal/wire away from
machine or an arc welding machine.
the generating source.
• Adopt the shielding wire.
11. Checking procedure for PCB (Printed Circuit Board)
The indoor PCB (Printed Circuit Board) have functions to check the signal transmission and reception of the serial circuit
and to check the microcomputer operation. (Self-diagnosis function)
●
Precautions required when checking
1. After turning off the power to the indoor unit, remove the inter-unit control wiring (U1-U2) and create a short-circuit
between U1 and U2.
2. Short the CHECK PIN on the PCB (Printed Circuit Board) of the indoor unit and turn on the power.
11-1. Checking the serial circuit
Indoor PCB (Printed Circuit Board) : A lighted LED indicates normal. A blinking LED indicates abnormal.
Outdoor PCB (Printed Circuit Board) : Blinking LEDs (D001 and D083) indicate normal. If one of the LEDs (D001 and
D083) goes off, it indicates abnormal.
11-2. Checking microcomputer operation
When the microcomputer works normally, the relays are switched in sequence as below.
Indoor PCB (Printed Circuit Board)
Output
ON time
Indoor fan Very high fan speed (HH)
0.5 seconds
Indoor fan High fan speed (H)
0.5 seconds
Indoor fan Low fan speed (L)
0.5 seconds
Indoor fan Very low fan speed (LL)
0.5 seconds
Drain pump
0.5 seconds
Operation order Operation signal
0.5 seconds
Alarm LED
0.5 seconds
Electronic expansion valve A
0.5 seconds
Electronic expansion valve B
0.5 seconds
Electronic expansion valve.A
0.5 seconds
Electronic expansion valve B
0.5 seconds