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NATE Air Conditioning Troubleshooting

Instructions:

Answer 50 questions in 15 minutes.
If you are not ready to take this test, you can study here.
Match each statement with the correct term.
Don't refresh. All questions and answers are randomly picked and ordered every time you load a test.

This is a study tool. The 3 wrong answers for each question are randomly chosen from answers to other questions. So, you might find at times the answers obvious, but you will see it re-enforces your understanding as you take the test each time.

1. An air conditioning unit has a suction line that is frosted up to the compressor. What faults could cause this to occur...
The system has been overcharged+The system has air trapped in the condenser
High superheat and low discharge pressure
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
The superheat will increase and the low-side pressure will decrease

2. What are two common symptoms of a rooftop air conditioning system that operates with a reverse-acting high-pressure control stuck in the closed position...
Technician B
A blown fuse
Both technicians are correct
Condenser fans operating during a low ambient condition and a low suction pressure

3. A commercial customer calls on a 90
Rise more than normal
Technician A is correct
The system has been overcharged+The system has air trapped in the condenser
Dirty condenser - bent condenser fins - and air recirculating over the condenser

4. Insufficient airflow can be caused by...
An increase of air leakage from ductwork
An increase in suction pressure and an increase in discharge pressure
A plugged filter drier
It keeps a constant superheat in the evaporator

5. What problem can cause an increase of discharge pressure and an increase of suction pressure...
Contains a solenoid coil and one or more sets of contacts
An acid-core suction line drier
An overcharged system
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay

6. A customer calls with an insufficient cooling complaint on a 90
Always have some liquid present in the bulb and diaphragm
The sight glass is full of liquid+the sight glass is full of gas
Clean the condenser coil
Technician B

7. A customer calls and complains that his air conditioning system is not operating properly. It is noticed that the compressor is not operating. A check on the run capacitor shows that there is 33 uf and the rating on the capacitor is 40 uf. Technician
An uninsulated TXV sensing bulb
Technician B
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
An increase in suction pressure and an increase in discharge pressure

8. The technician observes that the compressor is not operating. The compressor windings read 5 ohms start to run - run to common is opened - and start to common is opened. The technician concludes that...
A vacuum test+oil traces around fittings+soap bubble solution
Bad compressor valve
Technician B
The internal overload is opened

9. What problem or problems can cause low discharge and suction pressure...
An undercharged system+insufficient airflow over the evaporator coil
Rise more than normal
110-120
Clean the condenser coil

10. What are two common symptoms of refrigerant leaks in an air conditioning system...
Partially frosted evaporator and high superheat
Bad compressor valve
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil
Both technicians are correct

11. A liquid-charged TXV bulb will...
Clean the condenser coil
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
Always have some liquid present in the bulb and diaphragm
A dirty condenser - recirculation of condenser air - and a defective condenser fan

12. Technician A says that if you connect 208 volts to the primary side of a 240-volt/ 24-volt transformer - the transformer will burn out. Technician B says that if you connect 208 volts to the primary side of a 240-volt/24-volt transformer - the contro
An uninsulated TXV sensing bulb
The superheat increases and the subcooling decreases
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
Technician B

13. What is the purpose of a CPR valve...
Run with high head and high suction pressure
110-120
The oil pump pressure and the crankcase pressure
It is used to control refrigerant pressure in the compressor crankcase

14. What is a common discharge temperature of an air-cooled air conditioning system that is used on a 90
110-120
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
3 psig
An uninsulated suction line and a restricted metering device

15. Which of the following can cause excessive subcooling...
The sight glass is full of liquid+the sight glass is full of gas
50-65
An overcharged system
Evaporator and compressor

16. What type of problems can be caused by an oversized air conditioning system...
It would cause the low-side pressure to decrease
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
Both technicians are correct
Short cycling and insufficient dehumidification

17. A system that is being serviced has been evacuated down to 500 microns. When the gauges are closed and the vacuum pump is turned off - the pressure starts to increase and stops at 1000 microns. Technician A says that the system has a leak and needs t
It keeps a constant superheat in the evaporator
The internal overload is opened
Technician B
Clean the condenser coil

18. A commercial customer calls complaining that her rooftop air conditioning system is not operating. The technician arrives on the job and sets the thermostat to cooling - then notices that the indoor fan is not operating. The technician then sets the

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19. What problem or problems can cause low discharge and suction pressure...
An increase in low-side pressure
A missing air filter+improper rotation of the indoor blower+blower too small
An undercharged system+insufficient airflow over the evaporator coil
The superheat will increase and the low-side pressure will decrease

20. What are the symptoms of an air conditioning system that has a low charge...
Both technicians are correct
The low-side pressure will decrease and the evaporator coil will be partially frosted
Increases starting torque
An undercharged system+insufficient airflow over the evaporator coil

21. What are the symptoms of an air conditioning system that has a bad compressor discharge valve...
Technician B
Low discharge pressure - high suction pressure - and low amp draw
Dirty condenser - bent condenser fins - and air recirculating over the condenser
An increase in suction pressure and an increase in discharge pressure

22. What are two common symptoms of an overcharged air conditioning system that uses a capillary-tube-type metering device...
Technician B
An increase in suction pressure and an increase in discharge pressure
Both technicians are correct
A plugged filter drier

23. The internal overload of an air conditioning compressor senses winding temperature and...
A defective circuit breaker
An undercharge and low ambient conditions
Current in the compressor circuit
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor

24. A customer calls to complain that his central air conditioning system is not cooling properly. The technician arrives on the job. He or she notices that the indoor blower has adequate airflow and the outdoor condenser fan is operating - but the compr
An open internal overload protector
('Y' and 'C') and ('G' and 'C')
Lack of airflow
('Y' and 'C') and ('G' and 'C')

25. Which of the following will cause excessive discharge pressures on an air conditioning system...
Broken rings+broken valves+seized bearings
('Y' and 'C') and ('G' and 'C')
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
The discharge pressure increases and the amperage increases

26. The technician observes a pressure drop of 25 degrees across an air conditioning evaporator coil at start-up. This drop would indicate...
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
Lack of airflow
A sensing bulb improperly connected to the suction line
Always have some liquid present in the bulb and diaphragm

27. A customer calls with an insufficient cooling complaint. Upon arrival to the service call it is found that the system is using are-22 with the high-side pressure at 290 psig and the low-side pressure at 85 psig. The ambient temperature is 85
Technician A
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
Bad compressor valve
Technician B

28. Air filters should be replaced...
Whenever necessary
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
Increases starting torque
The system has been overcharged+The system has air trapped in the condenser

29. A restricted air filter in an air conditioning system can be identified by...
Both technicians are incorrect
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil
Technician B
Low superheat

30. What controls are used on air conditioning or refrigeration systems that incorporate an automatic pump-down system...
The sight glass is full of liquid+the sight glass is full of gas
High superheat and low discharge pressure
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
An increase of air leakage from ductwork

31. What are three methods for controlling a system's high-side pressure during low ambient conditions...
Bad compressor valve
Low discharge pressure - high suction pressure - and low amp draw
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
Flooding the condenser - cycling condenser fans - and dampering condenser air

32. What type of problems can be caused by an oversized air conditioning system...
Short cycling and insufficient dehumidification
Increases starting torque
A restricted metering device
Both technicians are correct

33. A compressor having tight bearings would cause the current value to...
The low-side pressure will decrease and the evaporator coil will be partially frosted
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
Low superheat
Rise more than normal

34. Which of the following is a common cause of an excessively low superheat on a TXV system...
Technician B
Technician B
A sensing bulb improperly connected to the suction line
The oil pump pressure and the crankcase pressure

35. If a rooftop air conditioning system does not have any means of low ambient protection - what will be two symptoms of the system when operating under a low ambient condition...
The low-side pressure will decrease and the evaporator coil will be partially frosted
110-120
High superheat and low discharge pressure
Partially frosted evaporator and high superheat

36. When using a vapor-charged TXV bulb - it is necessary to have...
Low discharge pressure - high suction pressure - and low amp draw
It keeps a constant superheat in the evaporator
The sensing bulb at a lower temperature than the valve body
An increase of air leakage from ductwork

37. What are two common problems that can cause a sight glass in an air conditioning to have bubbles...
An undercharge and low ambient conditions
A restricted metering device
It would cause the low-side pressure to decrease
Increases starting torque

38. An air conditioning system that uses a fan center has an inoperable indoor blower. When the thermostat is set for cooling and dialed below room temperature - a test with the voltmeter shows that there is 24 volts across terminals 'are' and 'G' at the
A plugged filter drier
A bad thermostat
Technician B
An increase in low-side pressure

39. What types of symptoms will be present if the sensing bulb of a TXV is not properly connected...
A bad thermostat
A vacuum test+oil traces around fittings+soap bubble solution
Both technicians are incorrect
High suction pressure and low superheat

40. Which of the following is a common cause of an excessively low superheat on a TXV system...
A sensing bulb improperly connected to the suction line
It would cause the low-side pressure to decrease
'G' to 'C'
Technician A

41. Name two symptoms that are common to an over-charged air conditioning system and a system that has a dirty condenser.
The discharge pressure increases and the amperage increases
Contains a solenoid coil and one or more sets of contacts
Technician A is correct
The sensing bulb at a lower temperature than the valve body

42. A 220-volt 30-amp motor circuit keeps tripping the breaker after the motor is started. The starting amperage is 60 amps. When measuring the amperage of the circuit - This is drawn for a brief moment. After startup - the amperage drops to 22 amps and
An undercharge and low ambient conditions
A defective circuit breaker
The sensing bulb at a lower temperature than the valve body
The low-side pressure will decrease and the evaporator coil will be partially frosted

43. What is the common cause of a compressor burnout...
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser
Contains a solenoid coil and one or more sets of contacts
Partially frosted evaporator and high superheat
('Y' and 'C') and ('G' and 'C')

44. Technician A says that to manually pump down an air conditioning system with a two-position service valve - the liquid line must be front-seated and the high- and low-side pressure will decrease to 0 psig when the pump-down is complete. Technician B
Technician A is correct
An uninsulated suction line and a restricted metering device
Evaporator and compressor
Technician A

45. A customer calls with an insufficient cooling complaint. Upon arrival to the service call it is found that the outdoor condensing unit is operating - but the indoor blower is not in operation. Technician A says that it is possible that it is a bad fu
Both technicians are incorrect
The oil pump pressure and the crankcase pressure
An increase in suction pressure and an increase in discharge pressure
A sensing bulb improperly connected to the suction line

46. If a TXV sensing bulb had lost its charge - what effect would this have on the air conditioning system...
An uninsulated suction line and a restricted metering device
An increase of air leakage from ductwork
It would cause the low-side pressure to decrease
A vacuum test+oil traces around fittings+soap bubble solution

47. A commercial customer calls complaining that her rooftop air conditioning system is not operating. The technician arrives on the job and sets the thermostat to cooling - then notices that the indoor fan is not operating. The technician then sets the

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48. If 24 volts are present to the contactor coil on an air conditioning system and the condenser fan or compressor is inoperative - which of the following could be at fault...
A blown fuse
Current in the compressor circuit
Both technicians are correct
The internal overload is opened

49. A hard-start kit for an air conditioning system...
A defective circuit breaker
3 psig
Increases starting torque
Bad compressor valve

50. When testing an indoor blower control circuit and the cooling circuit on a fan center - what terminals should read 24 volts if the air conditioning system is in operation...

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