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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 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
20 to 30
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
Both technicians are incorrect
A missing air filter+improper rotation of the indoor blower+blower too small

2. What problem can cause an increase of discharge pressure and an increase of suction pressure...
A blown fuse
An overcharged system
It would cause the low-side pressure to decrease
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged

3. What are three methods for controlling a system's high-side pressure during low ambient conditions...
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
The oil pump pressure and the crankcase pressure
Flooding the condenser - cycling condenser fans - and dampering condenser air

4. A restricted air filter in an air conditioning system can be identified by...
An open internal overload protector
Low superheat
A start relay
Technician B

5. When using a vapor-charged TXV bulb - it is necessary to have...
A missing air filter+improper rotation of the indoor blower+blower too small
The sensing bulb at a lower temperature than the valve body
An uninsulated suction line and a restricted metering device
Run with high head and high suction pressure

6. Which of the following can cause low superheat in a TXV system...
A low refrigerant charge
The internal overload is opened
Run with high head and high suction pressure
An uninsulated TXV sensing bulb

7. 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 A
An overcharged system
Clean the condenser coil
Current in the compressor circuit

8. What are the operating pressures of an oil pressure safety switch...
Current in the compressor circuit
Rise more than normal
A low refrigerant charge
The oil pump pressure and the crankcase pressure

9. 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
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
Rise more than normal
Short cycling and insufficient dehumidification

10. 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...
Clean the condenser coil
Condenser fans operating during a low ambient condition and a low suction pressure
A low refrigerant charge
A bad thermostat

11. What are two common symptoms of an overcharged air conditioning system that uses a capillary-tube-type metering device...
Condenser fans operating during a low ambient condition and a low suction pressure
The internal overload is opened
An increase in suction pressure and an increase in discharge pressure
3 psig

12. What are two common symptoms of refrigerant leaks in an air conditioning system...
Low superheat
Partially frosted evaporator and high superheat
110-120
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged

13. 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
The internal overload is opened
Evaporator and compressor

14. What is a common temperature difference between the condensing temperature on an air-cooled condensing unit and the outdoor ambient temperature...
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
Both technicians are incorrect
An increase in low-side pressure
20 to 30

15. 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...
High superheat and low discharge pressure
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
An open internal overload protector
A blown fuse

16. 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
Lack of airflow
Short cycling and insufficient dehumidification
The sensing bulb at a lower temperature than the valve body

17. 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
Short cycling and insufficient dehumidification
Broken rings+broken valves+seized bearings
Low voltage and a faulty start relay

18. What are the operating pressures of an oil pressure safety switch...
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil
High superheat and low discharge pressure
A bad thermostat
The oil pump pressure and the crankcase pressure

19. Which of the following will cause excessive discharge pressures on an air conditioning system...
An overcharged system
Evaporator and compressor
A start relay
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system

20. A customer calls with an insufficient cooling complaint on a 90
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
Technician B
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure

21. What causes the automatic expansion valve to close...
An increase in low-side pressure
3 psig
Partially frosted evaporator and high superheat
A dirty condenser - recirculation of condenser air - and a defective condenser fan

22. If a TXV sensing bulb had lost its charge - what effect would this have on the air conditioning system...
Increases starting torque
It would cause the low-side pressure to decrease
Short cycling and insufficient dehumidification
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system

23. The internal overload of an air conditioning compressor senses winding temperature and...
An undercharge and low ambient conditions
The oil pump pressure and the crankcase pressure
Current in the compressor circuit
An open internal overload protector

24. If a TXV sensing bulb had lost its charge - what effect would this have on the air conditioning system...
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
Technician B
It would cause the low-side pressure to decrease
An increase in low-side pressure

25. What problem or problems can cause low discharge and suction pressure...
An undercharged system+insufficient airflow over the evaporator coil
An uninsulated suction line and a restricted metering device
('Y' and 'C') and ('G' and 'C')
An open internal overload protector

26. When an air conditioning system has an undercharge - what happens to the superheat and the subcooling of the system...
Bad compressor valve
The discharge pressure increases and the amperage increases
The superheat increases and the subcooling decreases
Bad compressor valve

27. When an air conditioning system has an undercharge - what happens to the superheat and the subcooling of the system...
The superheat increases and the subcooling decreases
Evaporator and compressor
Flooding the condenser - cycling condenser fans - and dampering condenser air
Partially frosted evaporator and high superheat

28. What are the symptoms of a TXV air conditioning system if it has lost its charge...
The superheat will increase and the low-side pressure will decrease
An increase of air leakage from ductwork
A restricted metering device
20 to 30

29. On an are-22 air conditioning system - the suction-line filter drier should be changed when the pressure drop dictates...
The superheat increases and the subcooling decreases
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
3 psig
A start capacitor and a solid-state relay

30. 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
Low superheat
Technician B
A low refrigerant charge

31. What is the purpose of an EPR valve...
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
The oil pump pressure and the crankcase pressure
An increase in suction pressure and an increase in discharge pressure

32. 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
The low-side pressure will decrease and the evaporator coil will be partially frosted
Technician B
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
The sensing bulb at a lower temperature than the valve body

33. What are two common symptoms of an overcharged air conditioning system that uses a capillary-tube-type metering device...
Both technicians are incorrect
Broken rings+broken valves+seized bearings
An uninsulated suction line and a restricted metering device
An increase in suction pressure and an increase in discharge pressure

34. 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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35. 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
The external equalizer could be plugged
20 to 30
A defective circuit breaker
Technician B

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
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
A vacuum test+oil traces around fittings+soap bubble solution
Technician B
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay

37. When a high-efficiency split air conditioning system has a plugged metering device - what symptoms might occur...
A missing air filter+improper rotation of the indoor blower+blower too small
Both technicians are incorrect
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
High superheat and low discharge pressure

38. What are two common symptoms of refrigerant leaks in an air conditioning system...
A low refrigerant charge
Contains a solenoid coil and one or more sets of contacts
Both technicians are incorrect
Partially frosted evaporator and high superheat

39. What are two problems that can cause an air conditioning system to have an excessively high superheat...
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
An uninsulated suction line and a restricted metering device
An undercharged system+insufficient airflow over the evaporator coil
An undercharge and low ambient conditions

40. The temperature range of the suction line from an air conditioning system should be...
50-65
The sight glass is full of liquid+the sight glass is full of gas
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
It would cause the low-side pressure to decrease

41. 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...
High suction pressure and low superheat
The external equalizer could be plugged
Current in the compressor circuit
The internal overload is opened

42. 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...
Rise more than normal
Low voltage and a faulty start relay
An uninsulated TXV sensing bulb
Technician B

43. A system that uses a thermal electric expansion valve...
A sensing bulb improperly connected to the suction line
Technician B
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor

44. Which of the following could be the cause for a system's discharge and suction pressure being low...
Flooding the condenser - cycling condenser fans - and dampering condenser air
An overcharged system
A restricted metering device
Technician B

45. Which of the following problems can cause a decrease in a system's pressures and possible icing of the evaporator coil...
Both technicians are incorrect
'G' to 'C'
Condenser fans operating during a low ambient condition and a low suction pressure
A missing air filter+improper rotation of the indoor blower+blower too small

46. A liquid-charged TXV bulb will...
An overcharged system
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
Always have some liquid present in the bulb and diaphragm
Both technicians are incorrect

47. What type of problems can be caused by an oversized air conditioning system...
Flooding the condenser - cycling condenser fans - and dampering condenser air
An uninsulated TXV sensing bulb
Short cycling and insufficient dehumidification
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system

48. 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
Flooding the condenser - cycling condenser fans - and dampering condenser air
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication
Technician A
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system

49. When using a vapor-charged TXV bulb - it is necessary to have...
Increases starting torque
The sensing bulb at a lower temperature than the valve body
The superheat will increase and the low-side pressure will decrease
It keeps a constant superheat in the evaporator

50. What type of problems can be caused by an oversized air conditioning system...
Short cycling and insufficient dehumidification
The sensing bulb at a lower temperature than the valve body
It keeps a constant superheat in the evaporator
Current in the compressor circuit