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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 are the symptoms of an air conditioning system that has a bad compressor discharge valve...
The external equalizer could be plugged
It keeps a constant superheat in the evaporator
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
Low discharge pressure - high suction pressure - and low amp draw

2. 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...
Evaporator and compressor
Low voltage and a faulty start relay
Rise more than normal
Current in the compressor circuit

3. Which of the following can cause excessive subcooling...
Whenever necessary
The external equalizer could be plugged
An overcharged system
A start relay

4. Insufficient airflow can be caused by...
A defective circuit breaker
A vacuum test+oil traces around fittings+soap bubble solution
An increase of air leakage from ductwork
Short cycling and insufficient dehumidification

5. Air filters should be replaced...
It keeps a constant superheat in the evaporator
Both technicians are incorrect
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
Whenever necessary

6. On an are-22 air conditioning system - the suction-line filter drier should be changed when the pressure drop dictates...
Technician B
The discharge pressure increases and the amperage increases
Low voltage and a faulty start relay
3 psig

7. The technician observes a pressure drop of 25 degrees across an air conditioning evaporator coil at start-up. This drop would indicate...
110-120
An overcharged system
The oil pump pressure and the crankcase pressure
Lack of airflow

8. The technician observes a pressure drop of 25 degrees across an air conditioning evaporator coil at start-up. This drop would indicate...
The sensing bulb at a lower temperature than the valve body
Lack of airflow
A vacuum test+oil traces around fittings+soap bubble solution
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor

9. Which of the following can cause low superheat in a TXV system...
A missing air filter+improper rotation of the indoor blower+blower too small
An uninsulated TXV sensing bulb
A vacuum test+oil traces around fittings+soap bubble solution
A start relay

10. What are the symptoms of an air conditioning system that has a low charge...
Low voltage and a faulty start relay
A bad thermostat
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
The low-side pressure will decrease and the evaporator coil will be partially frosted

11. What is the purpose of the TXV...
Technician B
The internal overload is opened
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
It keeps a constant superheat in the evaporator

12. 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 increase in suction pressure and an increase in discharge pressure
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
Increases starting torque

13. A liquid-charged TXV bulb will...
Always have some liquid present in the bulb and diaphragm
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil
Technician B

14. Why is it unsafe to operate an air conditioning system with a low charge...
Technician A
Both technicians are incorrect
The superheat increases and the subcooling decreases
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication

15. 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
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication
Clean the condenser coil
The superheat increases and the subcooling decreases
The superheat increases and the subcooling decreases

16. What is a common temperature difference between the condensing temperature on an air-cooled condensing unit and the outdoor ambient temperature...
20 to 30
Low superheat
The low-side pressure will decrease and the evaporator coil will be partially frosted
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure

17. A compressor having tight bearings would cause the current value to...
The internal overload is opened
The sensing bulb at a lower temperature than the valve body
Dirty condenser - bent condenser fins - and air recirculating over the condenser
Rise more than normal

18. If a TXV sensing bulb had lost its charge - what effect would this have on the air conditioning system...
Technician A is correct
Both technicians are correct
A defective circuit breaker
It would cause the low-side pressure to decrease

19. 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...
A plugged filter drier
110-120
Condenser fans operating during a low ambient condition and a low suction pressure
Low voltage and a faulty start relay

20. A system that is operating with a clear sight glass shows...
Rise more than normal
Technician B
The sight glass is full of liquid+the sight glass is full of gas
Broken rings+broken valves+seized bearings

21. A customer calls with an insufficient cooling complaint on a 90
20 to 30
Technician B
An undercharge and low ambient conditions
Broken rings+broken valves+seized bearings

22. When a high-efficiency split air conditioning system has a plugged metering device - what symptoms might occur...
The oil pump pressure and the crankcase pressure
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
An acid-core suction line drier
Short cycling and insufficient dehumidification

23. What are three methods for controlling a system's high-side pressure during low ambient conditions...
High suction pressure and low superheat
Flooding the condenser - cycling condenser fans - and dampering condenser air
Low discharge pressure - high suction pressure - and low amp draw
An overcharged system

24. 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
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser
A bad thermostat
A missing air filter+improper rotation of the indoor blower+blower too small

25. 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
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
A start relay
Both technicians are incorrect
Broken rings+broken valves+seized bearings

26. What are the symptoms of a TXV air conditioning system if it has lost its charge...
Technician B
The superheat will increase and the low-side pressure will decrease
Increases starting torque
('Y' and 'C') and ('G' and 'C')

27. What types of symptoms will be present if the sensing bulb of a TXV is not properly connected...
Technician B
50-65
High suction pressure and low superheat
An increase in suction pressure and an increase in discharge pressure

28. Which of the following is a common cause of an excessively low superheat on a TXV system...
High superheat and low discharge pressure
The system has been overcharged+The system has air trapped in the condenser
A sensing bulb improperly connected to the suction line
20 to 30

29. What is the purpose of an EPR valve...
An uninsulated suction line and a restricted metering device
Evaporator and compressor
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
The oil pump pressure and the crankcase pressure

30. Insufficient airflow can be caused by...
A restricted metering device
An increase of air leakage from ductwork
Both technicians are incorrect
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system

31. 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...
Current in the compressor circuit
A blown fuse
It would cause the low-side pressure to decrease
20 to 30

32. What are the symptoms of an air conditioning system that has a bad compressor discharge valve...
An undercharged system+insufficient airflow over the evaporator coil
Short cycling and insufficient dehumidification
Low discharge pressure - high suction pressure - and low amp draw
A blown fuse

33. A rooftop package system keeps tripping out on the high-pressure switch. What are three possible causes for this problem...
The oil pump pressure and the crankcase pressure
A sensing bulb improperly connected to the suction line
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
Dirty condenser - bent condenser fins - and air recirculating over the condenser

34. What three things can prevent an air conditioning system from releasing heat at the proper rate...
A dirty condenser - recirculation of condenser air - and a defective condenser fan
The system has been overcharged+The system has air trapped in the condenser
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
Technician B

35. A system that is operating with a clear sight glass shows...
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
The internal overload is opened
The sight glass is full of liquid+the sight glass is full of gas
Evaporator and compressor

36. 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...
High superheat and low discharge pressure
The system has been overcharged+The system has air trapped in the condenser
Low discharge pressure - high suction pressure - and low amp draw
Current in the compressor circuit

37. A hard-start kit for an air conditioning system...
A blown fuse
Increases starting torque
The low-side pressure will decrease and the evaporator coil will be partially frosted
110-120

38. Which of the following will cause excessive discharge pressures on an air conditioning system...
3 psig
The sight glass is full of liquid+the sight glass is full of gas
Always have some liquid present in the bulb and diaphragm
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system

39. What are two common problems that can cause a sight glass in an air conditioning to have bubbles...
High suction pressure and low superheat
An undercharge and low ambient conditions
Flooding the condenser - cycling condenser fans - and dampering condenser air
High superheat and low discharge pressure

40. 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...
('Y' and 'C') and ('G' and 'C')
The internal overload is opened
It keeps a constant superheat in the evaporator
A plugged filter drier

41. A restricted air filter in an air conditioning system can be identified by...
An uninsulated TXV sensing bulb
Technician B
Low superheat
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay

42. 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
The sensing bulb at a lower temperature than the valve body
A bad thermostat
Low discharge pressure - high suction pressure - and low amp draw
Technician B

43. What problem can cause an increase of discharge pressure and an increase of suction pressure...
The sensing bulb at a lower temperature than the valve body
An overcharged system
Clean the condenser coil
An increase in low-side pressure

44. What are two common symptoms of an overcharged air conditioning system that uses a capillary-tube-type metering device...
The external equalizer could be plugged
Technician B
An increase in suction pressure and an increase in discharge pressure
Technician A

45. Which of the following is a possible cause for a compressor to overheat...
An open internal overload protector
An undercharge and low ambient conditions
It keeps a constant superheat in the evaporator
A low refrigerant charge

46. 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
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
Run with high head and high suction pressure

47. 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
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser
A restricted metering device
A plugged filter drier
Both technicians are incorrect

48. An air conditioning unit has a suction line that is frosted up to the compressor. What faults could cause this to occur...
Technician A
It would cause the low-side pressure to decrease
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
Technician A is correct

49. What controls are used on air conditioning or refrigeration systems that incorporate an automatic pump-down system...
An increase in low-side pressure
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
Technician B
50-65

50. What are two common symptoms of refrigerant leaks in an air conditioning system...
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
Technician B
Partially frosted evaporator and high superheat
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system