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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...
Whenever necessary
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
Technician A

2. 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
An open internal overload protector
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
The low-side pressure will decrease and the evaporator coil will be partially frosted

3. What problem can cause an increase of discharge pressure and an increase of suction pressure...
Bad compressor valve
An overcharged system
An increase in low-side pressure
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay

4. A rooftop package system keeps tripping out on the high-pressure switch. What are three possible causes for this problem...
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
High suction pressure and low superheat
Dirty condenser - bent condenser fins - and air recirculating over the condenser
A missing air filter+improper rotation of the indoor blower+blower too small

5. 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
A missing air filter+improper rotation of the indoor blower+blower too small
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
Technician B
Current in the compressor circuit

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
The external equalizer could be plugged
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
An overcharged system

7. What is a possible cause of a sweat or frost pattern downstream from a sight glass and filter dryer...
A bad thermostat
Dirty condenser - bent condenser fins - and air recirculating over the condenser
Low superheat
A plugged filter drier

8. A customer calls with an insufficient cooling complaint on a 90
The sensing bulb at a lower temperature than the valve body
Technician B
The oil pump pressure and the crankcase pressure
The external equalizer could be plugged

9. 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
It keeps a constant superheat in the evaporator
Technician A
The internal overload is opened
Both technicians are correct

10. Which of the following is a possible cause for a compressor to overheat...
A low refrigerant charge
Whenever necessary
The external equalizer could be plugged
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system

11. 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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12. 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 acid-core suction line drier
Both technicians are incorrect
Technician B
50-65

13. 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
Low discharge pressure - high suction pressure - and low amp draw
Technician B
Technician A is correct
It would cause the low-side pressure to decrease

14. 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
Clean the condenser coil
Bad compressor valve
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
Always have some liquid present in the bulb and diaphragm

15. 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
Technician B
An overcharged system
Clean the condenser coil
Both technicians are incorrect

16. What are common methods that are used for leak-testing a system...
A vacuum test+oil traces around fittings+soap bubble solution
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil
50-65
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure

17. A liquid-charged TXV bulb will...
Whenever necessary
Always have some liquid present in the bulb and diaphragm
It keeps a constant superheat in the evaporator
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system

18. What are two common problems that can cause a sight glass in an air conditioning to have bubbles...
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
An undercharge and low ambient conditions
110-120
It keeps a constant superheat in the evaporator

19. The temperature range of the suction line from an air conditioning system should be...
Technician B
50-65
The low-side pressure will decrease and the evaporator coil will be partially frosted
Technician A

20. What are the symptoms of a TXV air conditioning system if it has lost its charge...
High suction pressure and low superheat
The superheat will increase and the low-side pressure will decrease
Low discharge pressure - high suction pressure - and low amp draw
An overcharged system

21. 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
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
Current in the compressor circuit
The internal overload is opened
Both technicians are correct

22. A liquid-charged TXV bulb will...
Short cycling and insufficient dehumidification
An uninsulated TXV sensing bulb
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser
Always have some liquid present in the bulb and diaphragm

23. What are three methods for controlling a system's high-side pressure during low ambient conditions...
A low refrigerant charge
The oil pump pressure and the crankcase pressure
Flooding the condenser - cycling condenser fans - and dampering condenser air
An increase in suction pressure and an increase in discharge pressure

24. A customer calls with an insufficient cooling complaint on a 90
Both technicians are incorrect
Technician B
A defective circuit breaker
Increases starting torque

25. What are the operating pressures of an oil pressure safety switch...
The oil pump pressure and the crankcase pressure
An uninsulated TXV sensing bulb
A start capacitor and a solid-state relay
An uninsulated TXV sensing bulb

26. What controls are used on air conditioning or refrigeration systems that incorporate an automatic pump-down system...
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
Current in the compressor circuit
Bad compressor valve

27. 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...
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
An undercharged system+insufficient airflow over the evaporator coil
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil
Condenser fans operating during a low ambient condition and a low suction pressure

28. When a high-efficiency split air conditioning system has a plugged metering device - what symptoms might occur...
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser
A missing air filter+improper rotation of the indoor blower+blower too small
'G' to 'C'

29. 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
Run with high head and high suction pressure
50-65
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure

30. The best description of a relay would be...
Contains a solenoid coil and one or more sets of contacts
Technician B
Dirty condenser - bent condenser fins - and air recirculating over the condenser
High superheat and low discharge pressure

31. 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
Technician A is correct
Always have some liquid present in the bulb and diaphragm
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil

32. What causes the automatic expansion valve to close...
An overcharged system
An increase in low-side pressure
110-120
Low discharge pressure - high suction pressure - and low amp draw

33. What are two common symptoms of refrigerant leaks in an air conditioning system...
110-120
Technician B
It is used to control refrigerant pressure in the compressor crankcase
Partially frosted evaporator and high superheat

34. 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
The sensing bulb at a lower temperature than the valve body
Both technicians are incorrect
The oil pump pressure and the crankcase pressure
It is used to control refrigerant pressure in the compressor crankcase

35. What type of problems can be caused by an oversized air conditioning system...
An increase in suction pressure and an increase in discharge pressure
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
High superheat and low discharge pressure
Short cycling and insufficient dehumidification

36. 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
Run with high head and high suction pressure
Dirty condenser - bent condenser fins - and air recirculating over the condenser
Short cycling and insufficient dehumidification

37. Which of the following can cause low superheat in a TXV system...
Partially frosted evaporator and high superheat
50-65
An uninsulated TXV sensing bulb
The sensing bulb at a lower temperature than the valve body

38. An air conditioning unit has a suction line that is frosted up to the compressor. What faults could cause this to occur...
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
Technician A
A low refrigerant charge
It keeps a constant superheat in the evaporator

39. What causes the automatic expansion valve to close...
Technician B
Both technicians are incorrect
An increase in low-side pressure
It keeps a constant superheat in the evaporator

40. What is a common discharge temperature of an air-cooled air conditioning system that is used on a 90
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
Both technicians are correct
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser
110-120

41. 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 sensing bulb at a lower temperature than the valve body
A blown fuse
It is used to control refrigerant pressure in the compressor crankcase
The external equalizer could be plugged

42. What is a possible cause of a sweat or frost pattern downstream from a sight glass and filter dryer...
High suction pressure and low superheat
Contains a solenoid coil and one or more sets of contacts
A plugged filter drier
Low discharge pressure - high suction pressure - and low amp draw

43. 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 B
An overcharged system
3 psig
Technician A

44. 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
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
Broken rings+broken valves+seized bearings
Both technicians are incorrect
An uninsulated TXV sensing bulb

45. Which of the following will cause excessive discharge pressures on an air conditioning system...
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
Always have some liquid present in the bulb and diaphragm
Contains a solenoid coil and one or more sets of contacts
A bad thermostat

46. Superheat is found in an air conditioning system in the...
'G' to 'C'
The internal overload is opened
Evaporator and compressor
Technician B

47. 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...
Whenever necessary
An uninsulated TXV sensing bulb
The internal overload is opened
Low voltage and a faulty start relay

48. What problem or problems can cause the discharge pressure to be low and the suction pressure to be high...
Bad compressor valve
Low voltage and a faulty start relay
It keeps a constant superheat in the evaporator
('Y' and 'C') and ('G' and 'C')

49. 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 start relay
Technician B
A dirty condenser - recirculation of condenser air - and a defective condenser fan
A start capacitor and a solid-state relay

50. A commercial customer calls on a 90
Partially frosted evaporator and high superheat
A restricted metering device
The system has been overcharged+The system has air trapped in the condenser
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system