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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 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
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
3 psig
Technician A
An increase of air leakage from ductwork

2. Which of the following can cause excessive subcooling...
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
An overcharged system
A dirty condenser - recirculation of condenser air - and a defective condenser fan
Evaporator and compressor

3. 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
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil
A plugged filter drier
An increase in low-side pressure
The external equalizer could be plugged

4. What are two common problems that can cause a sight glass in an air conditioning to have bubbles...
An undercharge and low ambient conditions
The system has been overcharged+The system has air trapped in the condenser
Technician B
Short cycling and insufficient dehumidification

5. Insufficient airflow can be caused by...
Lack of airflow
It keeps a constant superheat in the evaporator
Clean the condenser coil
An increase of air leakage from ductwork

6. Name two symptoms that are common to an over-charged air conditioning system and a system that has a dirty condenser.
A bad thermostat
An uninsulated suction line and a restricted metering device
A vacuum test+oil traces around fittings+soap bubble solution
The discharge pressure increases and the amperage increases

7. What is a possible cause of a sweat or frost pattern downstream from a sight glass and filter dryer...
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
20 to 30
A plugged filter drier
Always have some liquid present in the bulb and diaphragm

8. 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 sensing bulb at a lower temperature than the valve body
A defective circuit breaker
Low voltage and a faulty start relay
Rise more than normal

9. A commercial customer calls on a 90
The system has been overcharged+The system has air trapped in the condenser
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
Technician B
Always have some liquid present in the bulb and diaphragm

10. Superheat is found in an air conditioning system in the...
Evaporator and compressor
An acid-core suction line drier
Both technicians are correct
A bad thermostat

11. An air conditioning system using a fixed-orifice metering device and with noncondensables in the system will cause...
Technician B
An overcharged system
An uninsulated suction line and a restricted metering device
Run with high head and high suction pressure

12. What are the symptoms of an air conditioning system that has a bad compressor discharge valve...
Low discharge pressure - high suction pressure - and low amp draw
Increases starting torque
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
Low voltage and a faulty start relay

13. 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
Partially frosted evaporator and high superheat
Low voltage and a faulty start relay
A vacuum test+oil traces around fittings+soap bubble solution
An open internal overload protector

14. A compressor having tight bearings would cause the current value to...
Rise more than normal
Increases starting torque
Lack of airflow
An increase in suction pressure and an increase in discharge pressure

15. On an are-22 air conditioning system - the suction-line filter drier should be changed when the pressure drop dictates...
3 psig
Technician B
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device

16. What are three methods for controlling a system's high-side pressure during low ambient conditions...
A bad thermostat
50-65
Flooding the condenser - cycling condenser fans - and dampering condenser air
An undercharged system+insufficient airflow over the evaporator coil

17. 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
20 to 30
Lack of airflow
An open internal overload protector

18. What are two problems that can cause an air conditioning system to have an excessively high superheat...
Technician B
The oil pump pressure and the crankcase pressure
A missing air filter+improper rotation of the indoor blower+blower too small
An uninsulated suction line and a restricted metering device

19. What component is most often the cause of a start capacitor failure...
It is used to control refrigerant pressure in the compressor crankcase
A bad thermostat
A start relay
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged

20. What are two common symptoms of an overcharged air conditioning system that uses a capillary-tube-type metering device...
Low superheat
An increase in suction pressure and an increase in discharge pressure
Contains a solenoid coil and one or more sets of contacts
Bad compressor valve

21. Which of the following is a possible cause for a compressor to overheat...
A low refrigerant charge
A restricted metering device
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser
Technician B

22. 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
Increases starting torque
Technician B
The oil pump pressure and the crankcase pressure
High superheat and low discharge pressure

23. 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
Evaporator and compressor
A start capacitor and a solid-state relay
A bad thermostat

24. The internal overload of an air conditioning compressor senses winding temperature and...
A blown fuse
Contains a solenoid coil and one or more sets of contacts
The sight glass is full of liquid+the sight glass is full of gas
Current in the compressor circuit

25. A hard-start kit for an air conditioning system...
A start relay
Increases starting torque
The sensing bulb at a lower temperature than the valve body
A low refrigerant charge

26. 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...
Run with high head and high suction pressure
A blown fuse
High superheat and low discharge pressure
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system

27. A restricted air filter in an air conditioning system can be identified by...
Low superheat
Technician B
A vacuum test+oil traces around fittings+soap bubble solution
The oil pump pressure and the crankcase pressure

28. What type of problems can be caused by an oversized air conditioning system...
Short cycling and insufficient dehumidification
A restricted metering device
Contains a solenoid coil and one or more sets of contacts
An overcharged system

29. 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
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
Technician A
The external equalizer could be plugged

30. Insufficient airflow can be caused by...
A dirty condenser - recirculation of condenser air - and a defective condenser fan
'G' to 'C'
Technician B
An increase of air leakage from ductwork

31. What is the purpose of the TXV...
It keeps a constant superheat in the evaporator
An uninsulated TXV sensing bulb
Rise more than normal
An increase in suction pressure and an increase in discharge pressure

32. 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
Run with high head and high suction pressure
A missing air filter+improper rotation of the indoor blower+blower too small
Bad compressor valve

33. A hard-start kit for an air conditioning system...
A bad thermostat
Increases starting torque
The sight glass is full of liquid+the sight glass is full of gas
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged

34. 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 acid-core suction line drier
Technician B
Low discharge pressure - high suction pressure - and low amp draw
Technician A

35. Which of the following will cause excessive discharge pressures on an air conditioning system...
'G' to 'C'
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
The superheat increases and the subcooling decreases
Evaporator and compressor

36. Which of the following problems can cause a decrease in a system's pressures and possible icing of the evaporator coil...
A missing air filter+improper rotation of the indoor blower+blower too small
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
It would cause the low-side pressure to decrease
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure

37. Air filters should be replaced...
The discharge pressure increases and the amperage increases
It is used to control refrigerant pressure in the compressor crankcase
Whenever necessary
Evaporator and compressor

38. What are the symptoms of an air conditioning system that has a low charge...
The low-side pressure will decrease and the evaporator coil will be partially frosted
A defective circuit breaker
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
An undercharge and low ambient conditions

39. A rooftop package system keeps tripping out on the high-pressure switch. What are three possible causes for this problem...
110-120
'G' to 'C'
An undercharged system+insufficient airflow over the evaporator coil
Dirty condenser - bent condenser fins - and air recirculating over the condenser

40. 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...
Broken rings+broken valves+seized bearings
Low voltage and a faulty start relay
Contains a solenoid coil and one or more sets of contacts
An overcharged system

41. 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...
Contains a solenoid coil and one or more sets of contacts
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil
A blown fuse

42. 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
High superheat and low discharge pressure
3 psig
Contains a solenoid coil and one or more sets of contacts
Technician B

43. 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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44. The technician observes a pressure drop of 25 degrees across an air conditioning evaporator coil at start-up. This drop would indicate...
A start relay
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
Lack of airflow
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system

45. Why is it unsafe to operate an air conditioning system with a low charge...
An overcharged system
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication
Condenser fans operating during a low ambient condition and a low suction pressure

46. The best description of a relay would be...
Contains a solenoid coil and one or more sets of contacts
A vacuum test+oil traces around fittings+soap bubble solution
Low superheat
Short cycling and insufficient dehumidification

47. What are two common symptoms of refrigerant leaks in an air conditioning system...
Partially frosted evaporator and high superheat
Evaporator and compressor
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
An undercharge and low ambient conditions

48. When using a vapor-charged TXV bulb - it is necessary to have...
An open internal overload protector
It would cause the low-side pressure to decrease
Increases starting torque
The sensing bulb at a lower temperature than the valve body

49. 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 uninsulated suction line and a restricted metering device
110-120
An undercharge and low ambient conditions

50. Which of the following problems can cause a decrease in a system's pressures and possible icing of the evaporator coil...
The sensing bulb at a lower temperature than the valve body
Run with high head and high suction pressure
An uninsulated TXV sensing bulb
A missing air filter+improper rotation of the indoor blower+blower too small