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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 three things can prevent an air conditioning system from releasing heat at the proper rate...
The discharge pressure increases and the amperage increases
Short cycling and insufficient dehumidification
Run with high head and high suction pressure
A dirty condenser - recirculation of condenser air - and a defective condenser fan

2. 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
Technician B
Current in the compressor circuit
Partially frosted evaporator and high superheat
Clean the condenser coil

3. What problem can cause an increase of discharge pressure and an increase of suction pressure...
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
An overcharged system
Low superheat
Technician B

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

5. What is the purpose of a CPR valve...
Evaporator and compressor
A low refrigerant charge
It is used to control refrigerant pressure in the compressor crankcase
The external equalizer could be plugged

6. What causes the automatic expansion valve to close...
An increase in low-side pressure
An increase in suction pressure and an increase in discharge pressure
A start relay
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser

7. 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
Bad compressor valve
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
Current in the compressor circuit
Technician B

8. On an are-22 air conditioning system - the suction-line filter drier should be changed when the pressure drop dictates...
3 psig
The superheat increases and the subcooling decreases
Technician B
Clean the condenser coil

9. 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
The system has been overcharged+The system has air trapped in the condenser
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
High superheat and low discharge pressure
Technician A is correct

10. The temperature range of the suction line from an air conditioning system should be...
50-65
Technician B
An overcharged system
High superheat and low discharge pressure

11. The temperature range of the suction line from an air conditioning system should be...
Low superheat
50-65
A missing air filter+improper rotation of the indoor blower+blower too small
The internal overload is opened

12. Which of the following can cause excessive subcooling...
An acid-core suction line drier
An overcharged system
The external equalizer could be plugged
The superheat increases and the subcooling decreases

13. What problem or problems can cause low discharge and suction pressure...
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
'G' to 'C'
An undercharged system+insufficient airflow over the evaporator coil
Clean the condenser coil

14. Which of the following could be the cause for a system's discharge and suction pressure being low...
A start capacitor and a solid-state relay
An increase in suction pressure and an increase in discharge pressure
A restricted metering device
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor

15. What causes the automatic expansion valve to close...
The sensing bulb at a lower temperature than the valve body
Dirty condenser - bent condenser fins - and air recirculating over the condenser
An increase in low-side pressure
Low discharge pressure - high suction pressure - and low amp draw

16. Insufficient airflow can be caused by...
A plugged filter drier
It would cause the low-side pressure to decrease
Current in the compressor circuit
An increase of air leakage from ductwork

17. What are the operating pressures of an oil pressure safety switch...
The oil pump pressure and the crankcase pressure
3 psig
A bad thermostat
The system has been overcharged+The system has air trapped in the condenser

18. What is the purpose of an EPR valve...
Condenser fans operating during a low ambient condition and a low suction pressure
The superheat will increase and the low-side pressure will decrease
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
Always have some liquid present in the bulb and diaphragm

19. Which of the following problems can cause a decrease in a system's pressures and possible icing of the evaporator coil...
Contains a solenoid coil and one or more sets of contacts
A start relay
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
A missing air filter+improper rotation of the indoor blower+blower too small

20. Why is it unsafe to operate an air conditioning system with a low charge...
Dirty condenser - bent condenser fins - and air recirculating over the condenser
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication
A blown fuse
Both technicians are incorrect

21. What are common methods that are used for leak-testing a system...
A vacuum test+oil traces around fittings+soap bubble solution
Short cycling and insufficient dehumidification
A missing air filter+improper rotation of the indoor blower+blower too small
Partially frosted evaporator and high superheat

22. 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 sight glass is full of liquid+the sight glass is full of gas
Technician B
Condenser fans operating during a low ambient condition and a low suction pressure
The discharge pressure increases and the amperage increases

23. 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
Contains a solenoid coil and one or more sets of contacts
It would cause the low-side pressure to decrease
A bad thermostat
The system has been overcharged+The system has air trapped in the condenser

24. What problem or problems can cause the discharge pressure to be low and the suction pressure to be high...
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
Low superheat
Bad compressor valve

25. A system that uses a thermal electric expansion valve...
'G' to 'C'
Both technicians are correct
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
The system has been overcharged+The system has air trapped in the condenser

26. Insufficient airflow can be caused by...
An increase of air leakage from ductwork
Technician B
The discharge pressure increases and the amperage increases
An increase in suction pressure and an increase in discharge pressure

27. A commercial customer calls on a 90
Low discharge pressure - high suction pressure - and low amp draw
The system has been overcharged+The system has air trapped in the condenser
An increase of air leakage from ductwork
It keeps a constant superheat in the evaporator

28. What are three methods for controlling a system's high-side pressure during low ambient conditions...
Both technicians are incorrect
A dirty condenser - recirculation of condenser air - and a defective condenser fan
Flooding the condenser - cycling condenser fans - and dampering condenser air
Dirty condenser - bent condenser fins - and air recirculating over the condenser

29. What controls are used on air conditioning or refrigeration systems that incorporate an automatic pump-down system...
An uninsulated suction line and a restricted metering device
An open internal overload protector
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
The sight glass is full of liquid+the sight glass is full of gas

30. What type of problems can be caused by an oversized air conditioning system...
Technician B
Short cycling and insufficient dehumidification
The oil pump pressure and the crankcase pressure
The superheat will increase and the low-side pressure will decrease

31. What problem or problems can cause the discharge pressure to be low and the suction pressure to be high...
Bad compressor valve
The oil pump pressure and the crankcase pressure
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
Current in the compressor circuit

32. What are the symptoms of an air conditioning system that has a low charge...
Low discharge pressure - high suction pressure - and low amp draw
A plugged filter drier
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil
The low-side pressure will decrease and the evaporator coil will be partially frosted

33. What are two problems that can cause an air conditioning system to have an excessively high superheat...
An uninsulated suction line and a restricted metering device
Low superheat
Short cycling and insufficient dehumidification
Increases starting torque

34. 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
Technician B
A low refrigerant charge
The discharge pressure increases and the amperage increases
50-65

35. 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...
Clean the condenser coil
Both technicians are incorrect
A blown fuse
A sensing bulb improperly connected to the suction line

36. Superheat is found in an air conditioning system in the...
An uninsulated TXV sensing bulb
The superheat will increase and the low-side pressure will decrease
A start capacitor and a solid-state relay
Evaporator and compressor

37. 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
Short cycling and insufficient dehumidification
Technician B
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor

38. 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
Contains a solenoid coil and one or more sets of contacts
A vacuum test+oil traces around fittings+soap bubble solution
A bad thermostat
An open internal overload protector

39. An air conditioning system using a fixed-orifice metering device and with noncondensables in the system will cause...
Lack of airflow
Condenser fans operating during a low ambient condition and a low suction pressure
Technician B
Run with high head and high suction pressure

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
A dirty condenser - recirculation of condenser air - and a defective condenser fan
An increase in suction pressure and an increase in discharge pressure
Technician B
The discharge pressure increases and the amperage increases

41. 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...
Technician B
Condenser fans operating during a low ambient condition and a low suction pressure
Low discharge pressure - high suction pressure - and low amp draw
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser

42. A compressor having tight bearings would cause the current value to...
Technician B
An undercharged system+insufficient airflow over the evaporator coil
Rise more than normal
The low-side pressure will decrease and the evaporator coil will be partially frosted

43. What are two common problems that can cause a sight glass in an air conditioning to have bubbles...
Lack of airflow
Both technicians are incorrect
An undercharge and low ambient conditions
An uninsulated TXV sensing bulb

44. What controls are used on air conditioning or refrigeration systems that incorporate an automatic pump-down system...
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
The superheat increases and the subcooling decreases
Broken rings+broken valves+seized bearings

45. Name two symptoms that are common to an over-charged air conditioning system and a system that has a dirty condenser.
The discharge pressure increases and the amperage increases
Clean the condenser coil
Both technicians are correct
An increase in low-side pressure

46. 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
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
Technician B
Condenser fans operating during a low ambient condition and a low suction pressure

47. Which of the following can cause low superheat in a TXV system...
An uninsulated TXV sensing bulb
The discharge pressure increases and the amperage increases
Lack of airflow
An uninsulated suction line and a restricted metering device

48. 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
Contains a solenoid coil and one or more sets of contacts
Bad compressor valve
The external equalizer could be plugged
Always have some liquid present in the bulb and diaphragm

49. Which of the following is a possible cause for a compressor to overheat...
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
A low refrigerant charge
110-120
('Y' and 'C') and ('G' and 'C')

50. 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
Bad compressor valve
Technician B
An overcharged system
It keeps a constant superheat in the evaporator