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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. What controls are used on air conditioning or refrigeration systems that incorporate an automatic pump-down system...
The oil pump pressure and the crankcase pressure
It would cause the low-side pressure to decrease
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
A sensing bulb improperly connected to the suction line

2. A liquid-charged TXV bulb will...
The system has been overcharged+The system has air trapped in the condenser
Always have some liquid present in the bulb and diaphragm
20 to 30
An open internal overload protector

3. What are common methods that are used for leak-testing a system...
3 psig
A vacuum test+oil traces around fittings+soap bubble solution
('Y' and 'C') and ('G' and 'C')
An undercharge and low ambient conditions

4. What type of problems can be caused by an oversized air conditioning system...
110-120
Technician B
Short cycling and insufficient dehumidification
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged

5. What problem or problems can cause low discharge and suction pressure...
Both technicians are incorrect
Lack of airflow
An undercharged system+insufficient airflow over the evaporator coil
Technician B

6. 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
Both technicians are incorrect
Always have some liquid present in the bulb and diaphragm
An uninsulated suction line and a restricted metering device
Technician B

7. What are two problems that can cause an air conditioning system to have an excessively high superheat...
Always have some liquid present in the bulb and diaphragm
An acid-core suction line drier
An uninsulated suction line and a restricted metering device
Whenever necessary

8. 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 defective circuit breaker
Technician B
Technician B

9. A system that is operating with a clear sight glass shows...
Technician B
An overcharged system
An increase of air leakage from ductwork
The sight glass is full of liquid+the sight glass is full of gas

10. A customer calls and complains that her high-efficiency air conditioning system is operating - but is not cooling properly. Further investigation shows that the system is using a TXV type of metering device. A subcooling check shows that the system a
The external equalizer could be plugged
A plugged filter drier
50-65
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay

11. What three things can prevent an air conditioning system from releasing heat at the proper rate...
A dirty condenser - recirculation of condenser air - and a defective condenser fan
Technician B
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
Contains a solenoid coil and one or more sets of contacts

12. 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...
Condenser fans operating during a low ambient condition and a low suction pressure
Short cycling and insufficient dehumidification
A bad thermostat
Technician B

13. What three things can prevent an air conditioning system from absorbing heat at the proper rate...
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil
A restricted metering device
Technician B
Technician B

14. Which of the following could be the cause for a system's discharge and suction pressure being low...
A restricted metering device
A dirty condenser - recirculation of condenser air - and a defective condenser fan
Partially frosted evaporator and high superheat
The sight glass is full of liquid+the sight glass is full of gas

15. What problem or problems can cause the discharge pressure to be low and the suction pressure to be high...
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
Technician B
Low voltage and a faulty start relay
Bad compressor valve

16. Which of the following is a possible cause for a compressor to overheat...
A low refrigerant charge
The discharge pressure increases and the amperage increases
A missing air filter+improper rotation of the indoor blower+blower too small
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil

17. What is the purpose of a CPR valve...
Technician B
Partially frosted evaporator and high superheat
It is used to control refrigerant pressure in the compressor crankcase
Low discharge pressure - high suction pressure - and low amp draw

18. The technician observes a pressure drop of 25 degrees across an air conditioning evaporator coil at start-up. This drop would indicate...
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
An overcharged system
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication
Lack of airflow

19. What causes the automatic expansion valve to close...
An increase in low-side pressure
A start capacitor and a solid-state relay
Partially frosted evaporator and high superheat
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay

20. A system that is operating with a clear sight glass shows...
The sensing bulb at a lower temperature than the valve body
('Y' and 'C') and ('G' and 'C')
An increase in suction pressure and an increase in discharge pressure
The sight glass is full of liquid+the sight glass is full of gas

21. 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
The external equalizer could be plugged
A plugged filter drier
Technician B
Both technicians are incorrect

22. A commercial customer calls on a 90
Technician B
An increase in suction pressure and an increase in discharge pressure
A dirty condenser - recirculation of condenser air - and a defective condenser fan
The system has been overcharged+The system has air trapped in the condenser

23. 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...
3 psig
Whenever necessary
Low voltage and a faulty start relay
Clean the condenser coil

24. A liquid-charged TXV bulb will...
Run with high head and high suction pressure
An undercharged system+insufficient airflow over the evaporator coil
Broken rings+broken valves+seized bearings
Always have some liquid present in the bulb and diaphragm

25. A hard-start kit consists of...
Technician B
The low-side pressure will decrease and the evaporator coil will be partially frosted
A start capacitor and a solid-state relay
Technician B

26. Which of the following can cause low superheat in a TXV system...
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil
Technician B
The low-side pressure will decrease and the evaporator coil will be partially frosted
An uninsulated TXV sensing bulb

27. 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 overcharged system
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
Technician B
3 psig

28. The internal overload of an air conditioning compressor senses winding temperature and...
Current in the compressor circuit
Technician B
Technician B
Low voltage and a faulty start relay

29. A technician arrives on the job and the customer complains that there is no cooling on his rooftop unit. Troubleshooting the system - the technician finds that the compressor is faulty. He notices that there is another faulty compressor laying next t
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
The low-side pressure will decrease and the evaporator coil will be partially frosted
A start relay
Broken rings+broken valves+seized bearings

30. What are the symptoms of an air conditioning system that has a bad compressor discharge valve...
A vacuum test+oil traces around fittings+soap bubble solution
An overcharged system
Both technicians are incorrect
Low discharge pressure - high suction pressure - and low amp draw

31. When an air conditioning system has an undercharge - what happens to the superheat and the subcooling of the system...
A start relay
A low refrigerant charge
The superheat increases and the subcooling decreases
Dirty condenser - bent condenser fins - and air recirculating over the condenser

32. On an are-22 air conditioning system - the suction-line filter drier should be changed when the pressure drop dictates...
Technician B
3 psig
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication
Low discharge pressure - high suction pressure - and low amp draw

33. Why is it unsafe to operate an air conditioning system with a low charge...
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication
The superheat will increase and the low-side pressure will decrease
Whenever necessary

34. What are two common symptoms of refrigerant leaks in an air conditioning system...
Clean the condenser coil
Both technicians are incorrect
Both technicians are incorrect
Partially frosted evaporator and high superheat

35. What are the symptoms of an air conditioning system that has a low charge...
High superheat and low discharge pressure
The system has been overcharged+The system has air trapped in the condenser
The low-side pressure will decrease and the evaporator coil will be partially frosted
Increases starting torque

36. What problem can cause an increase of discharge pressure and an increase of suction pressure...
A bad thermostat
An undercharged system+insufficient airflow over the evaporator coil
An overcharged system
Always have some liquid present in the bulb and diaphragm

37. 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
Current in the compressor circuit
It keeps a constant superheat in the evaporator
Clean the condenser coil
Both technicians are correct

38. What are two common symptoms of refrigerant leaks in an air conditioning system...
Condenser fans operating during a low ambient condition and a low suction pressure
Partially frosted evaporator and high superheat
('Y' and 'C') and ('G' and 'C')
The low-side pressure will decrease and the evaporator coil will be partially frosted

39. Which of the following is a common cause of an excessively low superheat on a TXV system...
'G' to 'C'
High superheat and low discharge pressure
A sensing bulb improperly connected to the suction line
A vacuum test+oil traces around fittings+soap bubble solution

40. 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
Both technicians are incorrect
Low superheat
An uninsulated TXV sensing bulb
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system

41. What is the common cause of a compressor burnout...
Technician A
Contains a solenoid coil and one or more sets of contacts
A sensing bulb improperly connected to the suction line
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser

42. 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
A missing air filter+improper rotation of the indoor blower+blower too small
The external equalizer could be plugged
Low voltage and a faulty start relay

43. Which of the following will cause excessive discharge pressures on an air conditioning system...
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
It would cause the low-side pressure to decrease
Technician B

44. A customer calls and complains that her high-efficiency air conditioning system is operating - but is not cooling properly. Further investigation shows that the system is using a TXV type of metering device. A subcooling check shows that the system a
Current in the compressor circuit
Rise more than normal
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

45. What problem or problems can cause the discharge pressure to be low and the suction pressure to be high...
An uninsulated suction line and a restricted metering device
Low voltage and a faulty start relay
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser
Bad compressor valve

46. The best description of a relay would be...
The low-side pressure will decrease and the evaporator coil will be partially frosted
Contains a solenoid coil and one or more sets of contacts
An overcharged system
An undercharged system+insufficient airflow over the evaporator coil

47. 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
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
20 to 30
110-120
Technician B

48. 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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49. What is the purpose of the TXV...
A start relay
It keeps a constant superheat in the evaporator
An undercharge and low ambient conditions
An overcharged system

50. What are the symptoms of a TXV air conditioning system if it has lost its charge...
An uninsulated suction line and a restricted metering device
The superheat will increase and the low-side pressure will decrease
The external equalizer could be plugged
Technician B