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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. 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...
A sensing bulb improperly connected to the suction line
The internal overload is opened
Clean the condenser coil
A dirty condenser - recirculation of condenser air - and a defective condenser fan

2. What controls are used on air conditioning or refrigeration systems that incorporate an automatic pump-down system...
Low superheat
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
Technician B
The low-side pressure will decrease and the evaporator coil will be partially frosted

3. What are the symptoms of an air conditioning system that has a low charge...
A vacuum test+oil traces around fittings+soap bubble solution
('Y' and 'C') and ('G' and 'C')
The superheat will increase and the low-side pressure will decrease
The low-side pressure will decrease and the evaporator coil will be partially frosted

4. On an are-22 air conditioning system - the suction-line filter drier should be changed when the pressure drop dictates...
3 psig
Technician B
The superheat will increase and the low-side pressure will decrease
A sensing bulb improperly connected to the suction line

5. 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 start relay
A blown fuse
An undercharged system+insufficient airflow over the evaporator coil
Both technicians are incorrect

6. Air filters should be replaced...
A defective circuit breaker
Technician B
Condenser fans operating during a low ambient condition and a low suction pressure
Whenever necessary

7. Why is it unsafe to operate an air conditioning system with a low charge...
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
A low refrigerant charge
A sensing bulb improperly connected to the suction line

8. 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
It is used to control refrigerant pressure in the compressor crankcase
3 psig
Rise more than normal

9. The technician observes a pressure drop of 25 degrees across an air conditioning evaporator coil at start-up. This drop would indicate...
('Y' and 'C') and ('G' and 'C')
Lack of airflow
Technician B
Short cycling and insufficient dehumidification

10. What is a possible cause of a sweat or frost pattern downstream from a sight glass and filter dryer...
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication
A bad thermostat
A plugged filter drier

11. What are two problems that can cause an air conditioning system to have an excessively high superheat...
Whenever necessary
A bad thermostat
It keeps a constant superheat in the evaporator
An uninsulated suction line and a restricted metering device

12. 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
50-65
It is used to control refrigerant pressure in the compressor crankcase
Technician B
Both technicians are incorrect

13. 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
Low superheat
Technician B
The superheat increases and the subcooling decreases

14. Why is it unsafe to operate an air conditioning system with a low charge...
Low superheat
Low superheat
Contains a solenoid coil and one or more sets of contacts
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication

15. What type of problems can be caused by an oversized air conditioning system...
'G' to 'C'
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication
Flooding the condenser - cycling condenser fans - and dampering condenser air
Short cycling and insufficient dehumidification

16. What is the purpose of the TXV...
A defective circuit breaker
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
It keeps a constant superheat in the evaporator

17. After a compressor motor has been severely burnt - What accessory must be added as an aid to rid the air conditioning system of acid...
An acid-core suction line drier
Both technicians are correct
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
A start relay

18. What problem can cause an increase of discharge pressure and an increase of suction pressure...
Partially frosted evaporator and high superheat
An uninsulated suction line and a restricted metering device
Whenever necessary
An overcharged system

19. 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
It is used to control refrigerant pressure in the compressor crankcase
The sight glass is full of liquid+the sight glass is full of gas
Technician B
An undercharged system+insufficient airflow over the evaporator coil

20. 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
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication
Increases starting torque
A vacuum test+oil traces around fittings+soap bubble solution

21. What type of problems can be caused by an oversized air conditioning system...
An open internal overload protector
Short cycling and insufficient dehumidification
Technician A is correct
Technician B

22. If a rooftop air conditioning system does not have any means of low ambient protection - what will be two symptoms of the system when operating under a low ambient condition...
Partially frosted evaporator and high superheat
The low-side pressure will decrease and the evaporator coil will be partially frosted
The system has been overcharged+The system has air trapped in the condenser
High superheat and low discharge pressure

23. A 220-volt 30-amp motor circuit keeps tripping the breaker after the motor is started. The starting amperage is 60 amps. When measuring the amperage of the circuit - This is drawn for a brief moment. After startup - the amperage drops to 22 amps and
The discharge pressure increases and the amperage increases
A defective circuit breaker
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser
High suction pressure and low superheat

24. 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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25. What are two common symptoms of refrigerant leaks in an air conditioning system...
The superheat increases and the subcooling decreases
50-65
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
Partially frosted evaporator and high superheat

26. Which of the following is a possible cause for a compressor to overheat...
An increase in low-side pressure
Technician B
A low refrigerant charge
High suction pressure and low superheat

27. 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 sight glass is full of liquid+the sight glass is full of gas
Broken rings+broken valves+seized bearings
The external equalizer could be plugged
A restricted metering device

28. Which of the following can cause excessive subcooling...
A defective circuit breaker
The low-side pressure will decrease and the evaporator coil will be partially frosted
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
An overcharged system

29. What is the purpose of a CPR valve...
It is used to control refrigerant pressure in the compressor crankcase
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
Whenever necessary

30. The technician observes a pressure drop of 25 degrees across an air conditioning evaporator coil at start-up. This drop would indicate...
Short cycling and insufficient dehumidification
Evaporator and compressor
3 psig
Lack of airflow

31. 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
The discharge pressure increases and the amperage increases
Both technicians are incorrect
Evaporator and compressor

32. 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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33. What are the symptoms of a TXV air conditioning system if it has lost its charge...
50-65
Rise more than normal
The superheat will increase and the low-side pressure will decrease
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil

34. What is a common discharge temperature of an air-cooled air conditioning system that is used on a 90
110-120
Short cycling and insufficient dehumidification
The system has been overcharged+The system has air trapped in the condenser
An increase of air leakage from ductwork

35. What are the symptoms of an air conditioning system that has a bad compressor discharge valve...
The oil pump pressure and the crankcase pressure
The external equalizer could be plugged
Low discharge pressure - high suction pressure - and low amp draw
The oil pump pressure and the crankcase pressure

36. 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 A
A defective circuit breaker
It is used to control refrigerant pressure in the compressor crankcase
The sight glass is full of liquid+the sight glass is full of gas

37. What problem or problems can cause the discharge pressure to be low and the suction pressure to be high...
Run with high head and high suction pressure
Flooding the condenser - cycling condenser fans - and dampering condenser air
The sight glass is full of liquid+the sight glass is full of gas
Bad compressor valve

38. What causes the automatic expansion valve to close...
The discharge pressure increases and the amperage increases
An increase in low-side pressure
A start relay
Low voltage and a faulty start relay

39. What are the operating pressures of an oil pressure safety switch...
Lack of airflow
The oil pump pressure and the crankcase pressure
20 to 30
20 to 30

40. 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 internal overload is opened
An undercharged system+insufficient airflow over the evaporator coil
An open internal overload protector

41. 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
Technician B
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
An increase in low-side pressure
Both technicians are correct

42. Which of the following is a common cause of an excessively low superheat on a TXV system...
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
Technician B
A sensing bulb improperly connected to the suction line
An uninsulated suction line and a restricted metering device

43. What are possible problems that can cause the discharge-line temperature on an air conditioning system to be cool to the touch...
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
A missing air filter+improper rotation of the indoor blower+blower too small
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication
A start relay

44. What problem or problems can cause low discharge and suction pressure...
Broken rings+broken valves+seized bearings
Low superheat
An increase in low-side pressure
An undercharged system+insufficient airflow over the evaporator coil

45. A compressor having tight bearings would cause the current value to...
A start relay
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
Rise more than normal
It would cause the low-side pressure to decrease

46. 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
An overcharged system
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
Technician B
An open internal overload protector

47. Which of the following problems can cause a decrease in a system's pressures and possible icing of the evaporator coil...
Condenser fans operating during a low ambient condition and a low suction pressure
A low refrigerant charge
A sensing bulb improperly connected to the suction line
A missing air filter+improper rotation of the indoor blower+blower too small

48. What is the purpose of the TXV...
A plugged filter drier
Low discharge pressure - high suction pressure - and low amp draw
Rise more than normal
It keeps a constant superheat in the evaporator

49. Superheat is found in an air conditioning system in the...
Both technicians are incorrect
Evaporator and compressor
An undercharge and low ambient conditions
'G' to 'C'

50. 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
An uninsulated TXV sensing bulb
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication
A bad thermostat
The sight glass is full of liquid+the sight glass is full of gas