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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
Run with high head and high suction pressure
An open internal overload protector
Technician B
It is used to control refrigerant pressure in the compressor crankcase

2. What causes the automatic expansion valve to close...
Technician B
A low refrigerant charge
An open internal overload protector
An increase in low-side pressure

3. The best description of a relay would be...
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser
A defective circuit breaker
Contains a solenoid coil and one or more sets of contacts
Low superheat

4. When using a vapor-charged TXV bulb - it is necessary to have...
A start relay
The sensing bulb at a lower temperature than the valve body
High superheat and low discharge pressure
Technician B

5. A system that uses a thermal electric expansion valve...
A vacuum test+oil traces around fittings+soap bubble solution
The oil pump pressure and the crankcase pressure
An undercharge and low ambient conditions
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system

6. An air conditioning unit has a suction line that is frosted up to the compressor. What faults could cause this to occur...
Technician B
Bad compressor valve
An undercharge and low ambient conditions
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay

7. What problem or problems can cause the discharge pressure to be low and the suction pressure to be high...
The superheat increases and the subcooling decreases
Flooding the condenser - cycling condenser fans - and dampering condenser air
Bad compressor valve
The external equalizer could be plugged

8. What are the symptoms of an air conditioning system that has a low charge...
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
Technician B
The low-side pressure will decrease and the evaporator coil will be partially frosted
Low discharge pressure - high suction pressure - and low amp draw

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
Both technicians are correct
Partially frosted evaporator and high superheat
A start capacitor and a solid-state relay
A sensing bulb improperly connected to the suction line

10. 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
Technician B
A bad thermostat
An increase of air leakage from ductwork
Technician B

11. 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 system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
It is used to control refrigerant pressure in the compressor crankcase
The superheat increases and the subcooling decreases
Low voltage and a faulty start relay

12. 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
Technician B
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system

13. What component is most often the cause of a start capacitor failure...
Evaporator and compressor
A vacuum test+oil traces around fittings+soap bubble solution
Both technicians are correct
A start relay

14. What are the operating pressures of an oil pressure safety switch...
An overcharged system
The sensing bulb at a lower temperature than the valve body
The oil pump pressure and the crankcase pressure
Short cycling and insufficient dehumidification

15. What problem can cause an increase of discharge pressure and an increase of suction pressure...
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
An overcharged system
Technician B
Rise more than normal

16. 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 increase of air leakage from ductwork
An overcharged system
A blown fuse
Technician B

17. What are the symptoms of a TXV air conditioning system if it has lost its charge...
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
Technician B
High superheat and low discharge pressure
The superheat will increase and the low-side pressure will decrease

18. What is a common temperature difference between the condensing temperature on an air-cooled condensing unit and the outdoor ambient temperature...
The internal overload is opened
20 to 30
A defective circuit breaker
Technician B

19. What are common methods that are used for leak-testing a system...
A vacuum test+oil traces around fittings+soap bubble solution
Clean the condenser coil
Technician B
3 psig

20. An air conditioning unit has a suction line that is frosted up to the compressor. What faults could cause this to occur...
A vacuum test+oil traces around fittings+soap bubble solution
A restricted metering device
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system

21. 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
A dirty condenser - recirculation of condenser air - and a defective condenser fan
High superheat and low discharge pressure
Evaporator and compressor

22. 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 was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
Evaporator and compressor
Technician A
It would cause the low-side pressure to decrease

23. 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
Technician B
The sight glass is full of liquid+the sight glass is full of gas
It is used to control refrigerant pressure in the compressor crankcase
An increase in suction pressure and an increase in discharge pressure

24. What is a common discharge temperature of an air-cooled air conditioning system that is used on a 90
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
An undercharged system+insufficient airflow over the evaporator coil
110-120
Both technicians are incorrect

25. After a compressor motor has been severely burnt - What accessory must be added as an aid to rid the air conditioning system of acid...
The system has been overcharged+The system has air trapped in the condenser
The discharge pressure increases and the amperage increases
An acid-core suction line drier
High suction pressure and low superheat

26. 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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27. What are two common problems that can cause a sight glass in an air conditioning to have bubbles...
Both technicians are incorrect
An undercharge and low ambient conditions
The low-side pressure will decrease and the evaporator coil will be partially frosted
An uninsulated suction line and a restricted metering device

28. After a compressor motor has been severely burnt - What accessory must be added as an aid to rid the air conditioning system of acid...
The internal overload is opened
It is used to control refrigerant pressure in the compressor crankcase
An acid-core suction line drier
Always have some liquid present in the bulb and diaphragm

29. 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
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
An increase of air leakage from ductwork
110-120

30. A restricted air filter in an air conditioning system can be identified by...
An uninsulated TXV sensing bulb
A restricted metering device
Low superheat
3 psig

31. 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
An increase of air leakage from ductwork
Technician A
Both technicians are correct
The oil pump pressure and the crankcase pressure

32. 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
The low-side pressure will decrease and the evaporator coil will be partially frosted
Partially frosted evaporator and high superheat
Technician B
Technician A

33. The technician observes a pressure drop of 25 degrees across an air conditioning evaporator coil at start-up. This drop would indicate...
A bad thermostat
Current in the compressor circuit
Lack of airflow
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure

34. On an are-22 air conditioning system - the suction-line filter drier should be changed when the pressure drop dictates...
Technician B
Short cycling and insufficient dehumidification
3 psig
An increase in low-side pressure

35. The internal overload of an air conditioning compressor senses winding temperature and...
Current in the compressor circuit
The superheat will increase and the low-side pressure will decrease
A low refrigerant charge
Rise more than normal

36. 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
An uninsulated TXV sensing bulb
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
Technician B
It is used to control refrigerant pressure in the compressor crankcase

37. 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
An acid-core suction line drier
A dirty condenser - recirculation of condenser air - and a defective condenser fan
Low discharge pressure - high suction pressure - and low amp draw

38. Which of the following can cause low superheat in a TXV system...
An uninsulated TXV sensing bulb
An overcharged system
The system has been overcharged+The system has air trapped in the condenser
The superheat will increase and the low-side pressure will decrease

39. Air filters should be replaced...
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
A dirty condenser - recirculation of condenser air - and a defective condenser fan
Technician B
Whenever necessary

40. 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
Technician B
Run with high head and high suction pressure
50-65
The sensing bulb at a lower temperature than the valve body

41. What are possible problems that can cause the discharge-line temperature on an air conditioning system to be cool to the touch...
A sensing bulb improperly connected to the suction line
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
Whenever necessary

42. 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...
The discharge pressure increases and the amperage increases
A restricted metering device
Condenser fans operating during a low ambient condition and a low suction pressure
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system

43. The temperature range of the suction line from an air conditioning system should be...
A bad thermostat
Technician B
Bad compressor valve
50-65

44. What are two problems that can cause an air conditioning system to have an excessively high superheat...
An uninsulated TXV sensing bulb
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
An uninsulated suction line and a restricted metering device
Technician B

45. What problem or problems can cause low discharge and suction pressure...
Short cycling and insufficient dehumidification
The superheat increases and the subcooling decreases
An undercharged system+insufficient airflow over the evaporator coil
Dirty condenser - bent condenser fins - and air recirculating over the condenser

46. When an air conditioning system has an undercharge - what happens to the superheat and the subcooling of the system...
Technician B
The superheat increases and the subcooling decreases
A defective circuit breaker
Technician A

47. If a TXV sensing bulb had lost its charge - what effect would this have on the air conditioning system...
The discharge pressure increases and the amperage increases
It would cause the low-side pressure to decrease
Flooding the condenser - cycling condenser fans - and dampering condenser air
('Y' and 'C') and ('G' and 'C')

48. What are two common problems that can cause a sight glass in an air conditioning to have bubbles...
50-65
An undercharge and low ambient conditions
3 psig
A restricted metering device

49. What type of problems can be caused by an oversized air conditioning system...
A sensing bulb improperly connected to the suction line
Always have some liquid present in the bulb and diaphragm
A dirty condenser - recirculation of condenser air - and a defective condenser fan
Short cycling and insufficient dehumidification

50. A hard-start kit consists of...
It keeps a constant superheat in the evaporator
A start capacitor and a solid-state relay
The sight glass is full of liquid+the sight glass is full of gas
An uninsulated TXV sensing bulb