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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. 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
A start relay
It would cause the low-side pressure to decrease
An open internal overload protector
Flooding the condenser - cycling condenser fans - and dampering condenser air

2. What three things can prevent an air conditioning system from releasing heat at the proper rate...
Current in the compressor circuit
A dirty condenser - recirculation of condenser air - and a defective condenser fan
Broken rings+broken valves+seized bearings
Technician B

3. What are three methods for controlling a system's high-side pressure during low ambient conditions...
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication
An overcharged system
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser
Flooding the condenser - cycling condenser fans - and dampering condenser air

4. What are the symptoms of an air conditioning system that has a bad compressor discharge valve...
An increase of air leakage from ductwork
A start capacitor and a solid-state relay
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
Low discharge pressure - high suction pressure - and low amp draw

5. 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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6. When an air conditioning system has an undercharge - what happens to the superheat and the subcooling of the system...
20 to 30
The superheat increases and the subcooling decreases
Bad compressor valve
Technician A

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
Whenever necessary
Technician B
Low discharge pressure - high suction pressure - and low amp draw
Technician A

8. A hard-start kit consists of...
Always have some liquid present in the bulb and diaphragm
Technician B
A start capacitor and a solid-state relay
It is used to control refrigerant pressure in the compressor crankcase

9. A liquid-charged TXV bulb will...
An uninsulated TXV sensing bulb
High suction pressure and low superheat
Always have some liquid present in the bulb and diaphragm
High suction pressure and low superheat

10. What problem or problems can cause low discharge and suction pressure...
High superheat and low discharge pressure
It keeps a constant superheat in the evaporator
An undercharged system+insufficient airflow over the evaporator coil
An uninsulated TXV sensing bulb

11. What are common methods that are used for leak-testing a system...
Technician B
A low refrigerant charge
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
A vacuum test+oil traces around fittings+soap bubble solution

12. A rooftop package system keeps tripping out on the high-pressure switch. What are three possible causes for this problem...
Technician B
Dirty condenser - bent condenser fins - and air recirculating over the condenser
An uninsulated TXV sensing bulb
It would cause the low-side pressure to decrease

13. Which of the following is a possible cause for a compressor to overheat...
A low refrigerant charge
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication
An acid-core suction line drier
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged

14. 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
High superheat and low discharge pressure
High superheat and low discharge pressure
Technician A is correct
The superheat increases and the subcooling decreases

15. Air filters should be replaced...
The sight glass is full of liquid+the sight glass is full of gas
Whenever necessary
A low refrigerant charge
Both technicians are incorrect

16. 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
The sensing bulb at a lower temperature than the valve body
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
Technician B
Low superheat

17. What is a common temperature difference between the condensing temperature on an air-cooled condensing unit and the outdoor ambient temperature...
The sight glass is full of liquid+the sight glass is full of gas
20 to 30
The superheat increases and the subcooling decreases
A start relay

18. What problem can cause an increase of discharge pressure and an increase of suction pressure...
110-120
The internal overload is opened
An overcharged system
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system

19. What is the purpose of the TXV...
It keeps a constant superheat in the evaporator
Partially frosted evaporator and high superheat
The sensing bulb at a lower temperature than the valve body
Evaporator and compressor

20. Which of the following can cause excessive subcooling...
Technician B
High suction pressure and low superheat
An overcharged system
The system has been overcharged+The system has air trapped in the condenser

21. What is a possible cause of a sweat or frost pattern downstream from a sight glass and filter dryer...
A plugged filter drier
20 to 30
Clean the condenser coil
The superheat will increase and the low-side pressure will decrease

22. Which of the following is a common cause of an excessively low superheat on a TXV system...
It is used to control refrigerant pressure in the compressor crankcase
A sensing bulb improperly connected to the suction line
Both technicians are correct
It keeps a constant superheat in the evaporator

23. What problem or problems can cause the discharge pressure to be low and the suction pressure to be high...
Broken rings+broken valves+seized bearings
Technician A
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil
Bad compressor valve

24. What problem or problems can cause low discharge and suction pressure...
The superheat increases and the subcooling decreases
A start capacitor and a solid-state relay
An undercharged system+insufficient airflow over the evaporator coil
Technician B

25. 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...
Low superheat
Both technicians are incorrect
Condenser fans operating during a low ambient condition and a low suction pressure
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system

26. What is the purpose of an EPR valve...
An undercharge and low ambient conditions
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
A bad thermostat
('Y' and 'C') and ('G' and 'C')

27. What causes the automatic expansion valve to close...
Short cycling and insufficient dehumidification
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
An increase in low-side pressure
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system

28. Name two symptoms that are common to an over-charged air conditioning system and a system that has a dirty condenser.
It keeps a constant superheat in the evaporator
Technician B
Low discharge pressure - high suction pressure - and low amp draw
The discharge pressure increases and the amperage increases

29. 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
('Y' and 'C') and ('G' and 'C')
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
A start capacitor and a solid-state relay
A bad thermostat

30. 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
An uninsulated suction line and a restricted metering device
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
Technician B
A vacuum test+oil traces around fittings+soap bubble solution

31. A split-system air conditioner that uses a piston-type metering device is to be charged with are-22. Technician A says that the outdoor dry-bulb temperature is needed to determine the proper superheat. Technician B says that the indoor wet-bulb tempe
A low refrigerant charge
Technician B
A dirty condenser - recirculation of condenser air - and a defective condenser fan
Both technicians are correct

32. What are the operating pressures of an oil pressure safety switch...
An increase of air leakage from ductwork
An uninsulated TXV sensing bulb
The oil pump pressure and the crankcase pressure
High superheat and low discharge pressure

33. A commercial customer calls on a 90
Both technicians are incorrect
The system has been overcharged+The system has air trapped in the condenser
The external equalizer could be plugged
High suction pressure and low superheat

34. A system that is operating with a clear sight glass shows...
50-65
Technician B
The sight glass is full of liquid+the sight glass is full of gas
Low voltage and a faulty start relay

35. Which of the following could be the cause for a system's discharge and suction pressure being low...
An undercharged system+insufficient airflow over the evaporator coil
('Y' and 'C') and ('G' and 'C')
The system has been overcharged+The system has air trapped in the condenser
A restricted metering device

36. Which of the following is a common cause of an excessively low superheat on a TXV system...
A defective circuit breaker
Both technicians are correct
A sensing bulb improperly connected to the suction line
An open internal overload protector

37. Which of the following can cause low superheat in a TXV system...
Partially frosted evaporator and high superheat
The low-side pressure will decrease and the evaporator coil will be partially frosted
An overcharged system
An uninsulated TXV sensing bulb

38. What is a common discharge temperature of an air-cooled air conditioning system that is used on a 90
Low superheat
Technician B
A blown fuse
110-120

39. What type of problems can be caused by an oversized air conditioning system...
The superheat increases and the subcooling decreases
An increase in low-side pressure
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
Short cycling and insufficient dehumidification

40. When a high-efficiency split air conditioning system has a plugged metering device - what symptoms might occur...
3 psig
110-120
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
A dirty condenser - recirculation of condenser air - and a defective condenser fan

41. 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
Clean the condenser coil
Technician B
Both technicians are incorrect
Always have some liquid present in the bulb and diaphragm

42. 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
Flooding the condenser - cycling condenser fans - and dampering condenser air
Technician B
An overcharged system

43. A compressor motor starts and operates for a short period of time and cycles on the external overload protector. What are two possible problems that could cause this...
The superheat increases and the subcooling decreases
An overcharged system
Low voltage and a faulty start relay
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser

44. A customer calls with an insufficient cooling complaint on a 90
Technician B
50-65
Bad compressor valve
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure

45. Insufficient airflow can be caused by...
A plugged filter drier
A dirty condenser - recirculation of condenser air - and a defective condenser fan
It is used to control refrigerant pressure in the compressor crankcase
An increase of air leakage from ductwork

46. Technician A says ' When charging a system using the superheat method - adding refrigerant to the system will increase the superheat.' Technician B says 'When charging a system using the superheat method - adding refrigerant will decrease the superhe
Technician B
An uninsulated suction line and a restricted metering device
An increase in low-side pressure
A plugged filter drier

47. A compressor having tight bearings would cause the current value to...
Flooding the condenser - cycling condenser fans - and dampering condenser air
Low discharge pressure - high suction pressure - and low amp draw
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser
Rise more than normal

48. 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...
The internal overload is opened
A start relay
Run with high head and high suction pressure
An uninsulated suction line and a restricted metering device

49. What are two common symptoms of an overcharged air conditioning system that uses a capillary-tube-type metering device...
An increase in suction pressure and an increase in discharge pressure
Run with high head and high suction pressure
Both technicians are correct
Technician A

50. A system that uses a thermal electric expansion valve...
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
Rise more than normal
Low discharge pressure - high suction pressure - and low amp draw
It keeps a constant superheat in the evaporator