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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. When troubleshooting a split-system air conditioner - it is found that the compressor motor is humming but not starting. Technician A says that it could be an open internal overload protector. Technician B says that it could be a blown fuse. Which te
The external equalizer could be plugged
Low discharge pressure - high suction pressure - and low amp draw
An acid-core suction line drier
Both technicians are incorrect

2. Which of the following can cause excessive subcooling...
An overcharged system
An increase of air leakage from ductwork
A bad thermostat
A plugged filter drier

3. What types of symptoms will be present if the sensing bulb of a TXV is not properly connected...
A dirty condenser - recirculation of condenser air - and a defective condenser fan
Technician B
Low discharge pressure - high suction pressure - and low amp draw
High suction pressure and low superheat

4. The internal overload of an air conditioning compressor senses winding temperature and...
An overcharged system
The oil pump pressure and the crankcase pressure
110-120
Current in the compressor circuit

5. If a TXV sensing bulb had lost its charge - what effect would this have on the air conditioning system...
It would cause the low-side pressure to decrease
A low refrigerant charge
Technician B
A dirty condenser - recirculation of condenser air - and a defective condenser fan

6. What are common methods that are used for leak-testing a system...
The sensing bulb at a lower temperature than the valve body
A vacuum test+oil traces around fittings+soap bubble solution
'G' to 'C'
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system

7. What are two common problems that can cause a sight glass in an air conditioning to have bubbles...
Short cycling and insufficient dehumidification
An undercharge and low ambient conditions
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
The low-side pressure will decrease and the evaporator coil will be partially frosted

8. Which of the following is a common cause of an excessively low superheat on a TXV system...
A vacuum test+oil traces around fittings+soap bubble solution
A sensing bulb improperly connected to the suction line
The discharge pressure increases and the amperage increases
Run with high head and high suction pressure

9. Which of the following can cause excessive subcooling...
Short cycling and insufficient dehumidification
Lack of airflow
Partially frosted evaporator and high superheat
An overcharged system

10. 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
An increase in low-side pressure
Technician A is correct
Current in the compressor circuit
The superheat increases and the subcooling decreases

11. A customer who owns a split air conditioning system complains that his system has been running but his house doesn't seem to be cooling properly. When the service technician arrives on the job - he or she finds that the indoor blower is operating and
A vacuum test+oil traces around fittings+soap bubble solution
Low superheat
Both technicians are correct
Clean the condenser coil

12. Which of the following will cause excessive discharge pressures on an air conditioning system...
Both technicians are correct
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system

13. When a high-efficiency split air conditioning system has a plugged metering device - what symptoms might occur...
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
3 psig
Bad compressor valve

14. What are three methods for controlling a system's high-side pressure during low ambient conditions...
Flooding the condenser - cycling condenser fans - and dampering condenser air
110-120
Increases starting torque
Low discharge pressure - high suction pressure - and low amp draw

15. What causes the automatic expansion valve to close...
Short cycling and insufficient dehumidification
20 to 30
An increase in low-side pressure
The superheat increases and the subcooling decreases

16. What problem can cause an increase of discharge pressure and an increase of suction pressure...
Both technicians are incorrect
50-65
A sensing bulb improperly connected to the suction line
An overcharged system

17. Which of the following problems can cause a decrease in a system's pressures and possible icing of the evaporator coil...
An open internal overload protector
A sensing bulb improperly connected to the suction line
Lack of airflow
A missing air filter+improper rotation of the indoor blower+blower too small

18. When a high-efficiency split air conditioning system has a plugged metering device - what symptoms might occur...
A low refrigerant charge
Technician A
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
Technician B

19. A rooftop package system keeps tripping out on the high-pressure switch. What are three possible causes for this problem...
A vacuum test+oil traces around fittings+soap bubble solution
Dirty condenser - bent condenser fins - and air recirculating over the condenser
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil
A low refrigerant charge

20. A customer calls and says that her air conditioning system is not cooling properly. Upon arrival - a technician notices that the suction line and compressor have frost buildup. Technician A says that the problem is probably a low charge. Technician B
Technician B
110-120
An acid-core suction line drier
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil

21. 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...
An acid-core suction line drier
A blown fuse
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication
The external equalizer could be plugged

22. 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
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
Increases starting torque

23. The technician observes a pressure drop of 25 degrees across an air conditioning evaporator coil at start-up. This drop would indicate...
Lack of airflow
Both technicians are incorrect
Technician B
Both technicians are incorrect

24. What is the common cause of a compressor burnout...
Broken rings+broken valves+seized bearings
A start relay
The external equalizer could be plugged
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser

25. What are possible problems that can cause the discharge-line temperature on an air conditioning system to be cool to the touch...
An overcharged system
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
The superheat will increase and the low-side pressure will decrease
An uninsulated TXV sensing bulb

26. What are the symptoms of a TXV air conditioning system if it has lost its charge...
Technician B
The superheat will increase and the low-side pressure will decrease
A sensing bulb improperly connected to the suction line
Run with high head and high suction pressure

27. Superheat is found in an air conditioning system in the...
An increase in low-side pressure
Clean the condenser coil
Evaporator and compressor
The superheat will increase and the low-side pressure will decrease

28. What are two common symptoms of an overcharged air conditioning system that uses a capillary-tube-type metering device...
Technician B
('Y' and 'C') and ('G' and 'C')
An increase in suction pressure and an increase in discharge pressure
Rise more than normal

29. 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
Both technicians are correct
An undercharge and low ambient conditions
Technician B
Lack of airflow

30. When troubleshooting a split-system air conditioner - it is found that the compressor motor is humming but not starting. Technician A says that it could be an open internal overload protector. Technician B says that it could be a blown fuse. Which te
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
A dirty condenser - recirculation of condenser air - and a defective condenser fan
An acid-core suction line drier
Both technicians are incorrect

31. An air conditioning system using a fixed-orifice metering device and with noncondensables in the system will cause...
Run with high head and high suction pressure
20 to 30
Condenser fans operating during a low ambient condition and a low suction pressure
A sensing bulb improperly connected to the suction line

32. What are the symptoms of an air conditioning system that has a low charge...
An undercharge and low ambient conditions
The low-side pressure will decrease and the evaporator coil will be partially frosted
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil
An increase in low-side pressure

33. A system that is operating with a clear sight glass shows...
The sight glass is full of liquid+the sight glass is full of gas
A restricted metering device
Evaporator and compressor
An undercharge and low ambient conditions

34. 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
Condenser fans operating during a low ambient condition and a low suction pressure
A dirty condenser - recirculation of condenser air - and a defective condenser fan
Clean the condenser coil

35. What is a common temperature difference between the condensing temperature on an air-cooled condensing unit and the outdoor ambient temperature...
The system has been overcharged+The system has air trapped in the condenser
High suction pressure and low superheat
It is used to control refrigerant pressure in the compressor crankcase
20 to 30

36. Air filters should be replaced...
Rise more than normal
Whenever necessary
High superheat and low discharge pressure
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged

37. What is the purpose of a CPR valve...
Technician B
It is used to control refrigerant pressure in the compressor crankcase
3 psig
Both technicians are incorrect

38. What are two common symptoms of refrigerant leaks in an air conditioning system...
Partially frosted evaporator and high superheat
3 psig
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

39. A compressor having tight bearings would cause the current value to...
Rise more than normal
The external equalizer could be plugged
An uninsulated suction line and a restricted metering device
A plugged filter drier

40. What problem or problems can cause the discharge pressure to be low and the suction pressure to be high...
Bad compressor valve
Both technicians are incorrect
'G' to 'C'
Always have some liquid present in the bulb and diaphragm

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
Technician B
Run with high head and high suction pressure
The internal overload is opened
The sight glass is full of liquid+the sight glass is full of gas

42. A technician receives an air conditioning service call stating that the system is operating but isn't cooling properly. When the technician arrives - she notices that the compressor has recently been changed and it is an are-22 system. She checks the
The system has been overcharged+The system has air trapped in the condenser
Broken rings+broken valves+seized bearings
The oil pump pressure and the crankcase pressure
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged

43. When an air conditioning system has an undercharge - what happens to the superheat and the subcooling of the system...
Rise more than normal
The superheat increases and the subcooling decreases
20 to 30
'G' to 'C'

44. 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
3 psig
Bad compressor valve
Technician B
A bad thermostat

45. When an air conditioning system has an undercharge - what happens to the superheat and the subcooling of the system...
A low refrigerant charge
The superheat increases and the subcooling decreases
The discharge pressure increases and the amperage increases
Technician B

46. A party-store owner tried to adjust the water valve on his water-cooled condensing unit - then he called for assistance from an HVAC/are service technician. It was found that when servicing the unit - the outlet water temperature was too low. Technic
High superheat and low discharge pressure
Technician B
A dirty condenser - recirculation of condenser air - and a defective condenser fan
An increase in suction pressure and an increase in discharge pressure

47. A system that is operating with a clear sight glass shows...
Partially frosted evaporator and high superheat
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
The sight glass is full of liquid+the sight glass is full of gas
It would cause the low-side pressure to decrease

48. What three things can prevent an air conditioning system from absorbing heat at the proper rate...
The system has been overcharged+The system has air trapped in the condenser
Both technicians are incorrect
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil
High superheat and low discharge pressure

49. What problem or problems can cause low discharge and suction pressure...
An increase of air leakage from ductwork
Contains a solenoid coil and one or more sets of contacts
The superheat increases and the subcooling decreases
An undercharged system+insufficient airflow over the evaporator coil

50. Name two symptoms that are common to an over-charged air conditioning system and a system that has a dirty condenser.
An uninsulated suction line and a restricted metering device
Short cycling and insufficient dehumidification
Whenever necessary
The discharge pressure increases and the amperage increases

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NATE Air Conditioning Troubleshooting

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