AUX air conditioner service manual
182
Chapter 7 Failure Analysis and Inspection of Electrical Control System
Air conditioner can be controlled by both strong-current circuit control panel and weak-current
electronic circuit control panel, control philosophies of which are different, so fault analysis
procedures of the two types shall be described separately:
Electrical system is the device to control and protect refrigerating system and fan system. Apart from
faults on electrical circuit, faults also may be resulted by the malfunction of refrigerating system and
fan system but be reflected through electrical control system. Therefore, refrigerating system and fan
system must be taken into consideration to analyze faults of electrical control system.
1. Strong Current Control System
Strong current control system is powered by single phase 220V or 380V service voltage, and with
relative simply controls circuit, fault inspection of strong current control system is not very difficult.
(1)Compressor and fan fails to operate
When switched on, compressor and fan fail to operate, faults of electrical circuits may include:
① Power failure
② Receptacle wire breakage
③ Fuse burns out
④ Loose contact of socket or receptacle
⑤ Service voltage is too low to make the motor operate, and then heat protector trips and cuts
off electrical power;
⑥ Wire breakage in option switch
⑦ Wire Breakage in Electrical Control Circuit resulted by improper operation, poor quality or
faults of refrigerating system and fan system; for example, fuse burns out may be resulted by
faults of refrigerating system and fan system besides wire contact and short circuit.
(2)Fan runs but compressor fails to operate
① Improper position of temperature Control knob;
② Contact of overload protective system breaks because refrigerating overloads during
operation and cause trip of protective system, or protective system can’t work properly
itself ;
③ Failure of compressor operation capacity resulted from improper maintenance or moisture.
④ Compressor motor burns out.
(3) Compressor starts and stops too frequently after air conditioner switches on
① Temperature sensor of temperature control system is installed too close to evaporator so that it
is impacted by evaporation temperature;
② Service voltage is instable because of instable electrical power network;
③ Poor contact of bimetal of overload protective system
(4)Long term continuous operation of compressor
① Because of too many heating appliances in the room, heat load of air conditioner is excessive
heavy;
② Contacts of temperature control system adhere to each other and cannot be broken off.
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