1. Service Section
Technical Training

2. Air Conditioning Troubleshooting

3. Air Conditioning System
An air conditioning system can be divided into 2 main functioning groups
Electrical circuit
Refrigerant circuit
Electrical - power supply, controls
Refrigerant - close circuit, components

4. Air Conditioning System
To troubleshoot a system, one must have to adopt “divide and conquer” technique
Divide the “Big” problem into multiple smaller problems
Solve each of the problem individually
Put electrical problem in first priority
A main point to take note is that if a system do not start, the faulty must be from electrical fault
Use software programming as an example

5. Troubleshooting electrical faults
Always ask a lot of questions and do not make assumption before we check
Is the power supply being switch on / being connected ?
Is the wiring being done properly?
Is the wire loose ?
Is there any signal coming from controller or thermostat ?
Must make sure that the power supply is

6. Troubleshooting electrical faults
1) Unit will not start
Main power supply fail ? Voltage fluctuation ?
Blown fuse or varistor ?
Faulty transformer ?
Loose connections ?
Shorted or broken wires ?
Safety device opens ?
No signal from thermostat/controller ?
Faulty thermostat ?
Must make sure that the power supply is

7. Troubleshooting electrical faults
2) Some components do not start
Loose connections ?
Shorted or broken wires ?
No signal from thermostat/controller ?
Faulty magnetic contactor ?
Must make sure that the power supply is

8. Troubleshooting electrical faults
3) Controller/thermostat
A clear understanding of the functional specification of the controller/thermostat is crucial.
Setting of the controller/thermostat must be obtained.
Operating temperatures must be obtained (exp: room, return air, ambient, water, etc.)
Must make sure that the power supply is

9. Troubleshooting refrigerant faults
Some of the major problems found in a air conditioning system
The air conditioner runs but shortly stops
The air conditioner short cycles with insufficient cooling
The air conditioner runs continuously with insufficient cooling
Must make sure that the power supply is

10. Troubleshooting refrigerant faults
Three main conditions in the air conditioners that are operating but not cooling satisfactorily are
High discharge pressure
Low suction pressure
High suction pressure
Must make sure that the power supply is

11. Troubleshooting refrigerant faults
1) High discharge pressure
Dirty or partially blocked condenser
Air or other non-condensable gases in refrigeration cycle
Overcharge of refrigerant
Insufficient condensing medium
High temperature condensing medium
Short cycling of condensing air
Must make sure that the power supply is

12. Troubleshooting refrigerant faults
2) Low suction pressure
Insufficient air or heat load on evaporator coil
Resistance against refrigerant flow
Shortage of refrigerant
Faulty capillary tube or expansion valve
Must make sure that the power supply is

13. Troubleshooting refrigerant faults
3) High suction pressure
Heavy load conditions
Unit undersized for application
Low superheat adjustment
Improper expansion valve adjustment
Poor installation of feeler bulb
inefficient compressor
Must make sure that the power supply is

14. Troubleshooting refrigerant faults
Some of the problems of refrigerant system can be diagnose through the use of pressure gauge and also an ammeter
Must make sure that the power supply is

15. Troubleshooting electrical faults
H.P
L.P
AMP
Pressure and running current reading
Both high and low pressure are very high
Running current increase extremely
Main causes of troubles
Refrigerant overcharged >> Wet operation
* In case refrigerant overcharged excessively, high pressure switch or overcurrent relay functions
Must make sure that the power supply is

16. Troubleshooting electrical faults
H.P
L.P
AMP
Pressure and running current reading
Discharge pressure is very high
Suction pressure is a little higher than normal
Running current increases
Main causes of troubles
Insufficient condensing medium
* Dirty condenser
* Partially blocked condenser
* Malfunction of condenser fan or fan motor
* Reverse revolution of condenser fan
* Short cycling of condensing air
* High temperature condensing air
Must make sure that the power supply is

17. Troubleshooting electrical faults
H.P
L.P
AMP
Pressure and running current reading
Discharge pressure is a little higher than normal
Suction pressure is very high
Running current increases
Main causes of troubles
Unit undersized for application
Heavy load condition
* High suction air temperature >> superheated operation
Excessive air flow rate
Excessively opened expansion valve >> wet operation
Must make sure that the power supply is
* Poor installation of feeler bulb
* Low superheat adjustment

18. Troubleshooting electrical faults
H.P
L.P
AMP
Pressure and running current reading
Discharge pressure is a little lower than normal
Suction pressure is very low
Running current decreases
* Frost grows on evaporator coil
Main causes of troubles
Shortage of refrigerant
Restricted refrigerant flow
>> superheated operation
* Expansion valve or capillary tube obstructed
* Dryer or filter clogged with dirt
* Valve in liquid line partially closed
* Obstruction in liquid line
* Leaking power element on expansion valve
Must make sure that the power supply is

19. Troubleshooting electrical faults
H.P
L.P
AMP
Pressure and running current reading
Discharge pressure is a little lower than normal
Suction pressure is very low
Running current decreases
* Frost grows on evaporator coil
Main causes of troubles (continue)
Insufficient heating medium >> wet operation
* Poor evaporating air flow rate
- Dirty air filter
- Slippage of fan belt
- Reverse revolution of evaporator fan
- Short cycling of cooling air
* Light load condition
- Low suction air temperature
Must make sure that the power supply is

20. Troubleshooting electrical faults
H.P
L.P
AMP
Pressure and running current reading
Discharge pressure is a little lower than normal
Suction pressure is very high
Running current decreases
Main causes of troubles
Malfunction of compressor >> super heated operation
Must make sure that the power supply is

21. Troubleshooting electrical faults
H.P
L.P
AMP
Pressure and running current reading
Both high and low pressures are very low
Running current decreases extremely
Main causes of troubles
Extreme refrigerant shortage >> super heated operation
Must make sure that the power supply is

22. Wet operation Liquid refrigerant comes back to the compressor
Liquid compression
Insufficient lubrication
(washed out)
Refrigerant is dissolved in oil
Motor coil insulation is being eroded
Oil foaming
Vane or valve failure
Motor coil failure
Bearing failure

23. Super heated operation
Suction and discharge gas temperature is higher than the normal
Oil temperature becomes higher
Carbonization of oil
Oil viscosity drops
Insufficient cooling for motor coil
Incomplete seat action
Insufficient lubrication
Motor coil failure
Bearing failure

24. Thank you