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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. Which of the following is a possible cause for a compressor to overheat...
A low refrigerant charge
A plugged filter drier
Technician B
Both technicians are incorrect

2. What problem or problems can cause low discharge and suction pressure...
20 to 30
An undercharged system+insufficient airflow over the evaporator coil
A defective circuit breaker
Technician B

3. 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...
'G' to 'C'
A blown fuse
Technician A is correct
Low superheat

4. The technician observes a pressure drop of 25 degrees across an air conditioning evaporator coil at start-up. This drop would indicate...
Lack of airflow
An overcharged system
Technician B
Low voltage and a faulty start relay

5. What three things can prevent an air conditioning system from absorbing heat at the proper rate...
An undercharged system+insufficient airflow over the evaporator coil
'G' to 'C'
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil
High suction pressure and low superheat

6. Air filters should be replaced...
110-120
Both technicians are incorrect
Whenever necessary
The low-side pressure will decrease and the evaporator coil will be partially frosted

7. What controls are used on air conditioning or refrigeration systems that incorporate an automatic pump-down system...
A vacuum test+oil traces around fittings+soap bubble solution
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
Low superheat

8. 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
A missing air filter+improper rotation of the indoor blower+blower too small
Contains a solenoid coil and one or more sets of contacts
Technician B
Rise more than normal

9. What is the purpose of the TXV...
The low-side pressure will decrease and the evaporator coil will be partially frosted
The external equalizer could be plugged
Run with high head and high suction pressure
It keeps a constant superheat in the evaporator

10. When using a vapor-charged TXV bulb - it is necessary to have...
A bad thermostat
A low refrigerant charge
The sensing bulb at a lower temperature than the valve body
110-120

11. What are two common problems that can cause a sight glass in an air conditioning to have bubbles...
Short cycling and insufficient dehumidification
The external equalizer could be plugged
An undercharged system+insufficient airflow over the evaporator coil
An undercharge and low ambient conditions

12. Name two symptoms that are common to an over-charged air conditioning system and a system that has a dirty condenser.
Technician B
Evaporator and compressor
The discharge pressure increases and the amperage increases
The low-side pressure will decrease and the evaporator coil will be partially frosted

13. 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
Always have some liquid present in the bulb and diaphragm
Low superheat
Both technicians are incorrect
'G' to 'C'

14. When using a vapor-charged TXV bulb - it is necessary to have...
Dirty condenser - bent condenser fins - and air recirculating over the condenser
The sensing bulb at a lower temperature than the valve body
A dirty condenser - recirculation of condenser air - and a defective condenser fan
Condenser fans operating during a low ambient condition and a low suction pressure

15. What are two common symptoms of an overcharged air conditioning system that uses a capillary-tube-type metering device...
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
Lack of airflow
An increase in suction pressure and an increase in discharge pressure

16. Which of the following could be the cause for a system's discharge and suction pressure being low...
('Y' and 'C') and ('G' and 'C')
A blown fuse
A restricted metering device
Low discharge pressure - high suction pressure - and low amp draw

17. Which of the following can cause low superheat in a TXV system...
An uninsulated TXV sensing bulb
A start capacitor and a solid-state relay
The discharge pressure increases and the amperage increases
The sensing bulb at a lower temperature than the valve body

18. A system that is operating with a clear sight glass shows...
The sight glass is full of liquid+the sight glass is full of gas
Flooding the condenser - cycling condenser fans - and dampering condenser air
Both technicians are correct
Whenever necessary

19. 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
An increase in suction pressure and an increase in discharge pressure
The internal overload is opened
Low superheat
Both technicians are incorrect

20. 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
A dirty condenser - recirculation of condenser air - and a defective condenser fan
Technician B
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
Low voltage and a faulty start relay

21. Which of the following is a common cause of an excessively low superheat on a TXV system...
A sensing bulb improperly connected to the suction line
Increases starting torque
A missing air filter+improper rotation of the indoor blower+blower too small
An increase in suction pressure and an increase in discharge pressure

22. What types of symptoms will be present if the sensing bulb of a TXV is not properly connected...
High suction pressure and low superheat
The superheat will increase and the low-side pressure will decrease
Whenever necessary
Technician B

23. When a high-efficiency split air conditioning system has a plugged metering device - what symptoms might occur...
The internal overload is opened
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
Both technicians are incorrect

24. 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 dirty condenser - recirculation of condenser air - and a defective condenser fan
An open internal overload protector
Always have some liquid present in the bulb and diaphragm

25. What component is most often the cause of a start capacitor failure...
A start relay
Evaporator and compressor
The superheat increases and the subcooling decreases
'G' to 'C'

26. 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 B
Technician A is correct
A vacuum test+oil traces around fittings+soap bubble solution
High suction pressure and low superheat

27. 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
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication
A blown fuse
An open internal overload protector
An increase in low-side pressure

28. 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
Whenever necessary
Bad compressor valve
The external equalizer could be plugged

29. 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
A start relay
An increase of air leakage from ductwork
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure

30. Which of the following can cause excessive subcooling...
A blown fuse
Technician B
An overcharged system
An uninsulated suction line and a restricted metering device

31. 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
3 psig
A vacuum test+oil traces around fittings+soap bubble solution
A bad thermostat
20 to 30

32. What types of symptoms will be present if the sensing bulb of a TXV is not properly connected...
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
Rise more than normal
A sensing bulb improperly connected to the suction line
High suction pressure and low superheat

33. A system that uses a thermal electric expansion valve...
The discharge pressure increases and the amperage increases
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
A plugged filter drier
Current in the compressor circuit

34. 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
It keeps a constant superheat in the evaporator
Broken rings+broken valves+seized bearings
An uninsulated TXV sensing bulb
An overcharged system

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
An open internal overload protector
The sight glass is full of liquid+the sight glass is full of gas
Technician B
Increases starting torque

36. 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
Technician B
An increase in suction pressure and an increase in discharge pressure
An increase of air leakage from ductwork

37. 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
A dirty condenser - recirculation of condenser air - and a defective condenser fan
A missing air filter+improper rotation of the indoor blower+blower too small
Clean the condenser coil

38. The best description of a relay would be...
20 to 30
Evaporator and compressor
Contains a solenoid coil and one or more sets of contacts
Broken rings+broken valves+seized bearings

39. A liquid-charged TXV bulb will...
A sensing bulb improperly connected to the suction line
Low voltage and a faulty start relay
Always have some liquid present in the bulb and diaphragm
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure

40. What are two common symptoms of refrigerant leaks in an air conditioning system...
Partially frosted evaporator and high superheat
A sensing bulb improperly connected to the suction line
The discharge pressure increases and the amperage increases
Rise more than normal

41. Which of the following could be the cause for a system's discharge and suction pressure being low...
Technician B
A restricted metering device
50-65
An increase in suction pressure and an increase in discharge pressure

42. 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...
The sight glass is full of liquid+the sight glass is full of gas
110-120
The internal overload is opened
Dirty condenser - bent condenser fins - and air recirculating over the condenser

43. What are the symptoms of an air conditioning system that has a low charge...
A restricted metering device
The low-side pressure will decrease and the evaporator coil will be partially frosted
The sight glass is full of liquid+the sight glass is full of gas
Contains a solenoid coil and one or more sets of contacts

44. What are the symptoms of an air conditioning system that has a bad compressor discharge valve...
Technician B
Low discharge pressure - high suction pressure - and low amp draw
It would cause the low-side pressure to decrease
Low voltage and a faulty start relay

45. 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
Technician B
An undercharge and low ambient conditions
A dirty condenser - recirculation of condenser air - and a defective condenser fan

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
Technician B
The superheat increases and the subcooling decreases
The external equalizer could be plugged
High superheat and low discharge pressure

47. What is a common temperature difference between the condensing temperature on an air-cooled condensing unit and the outdoor ambient temperature...
20 to 30
An overcharged system
Low superheat
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser

48. What is a possible cause of a sweat or frost pattern downstream from a sight glass and filter dryer...
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
A plugged filter drier
Technician B
Current in the compressor circuit

49. 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 defective circuit breaker
Technician B
Low voltage and a faulty start relay
3 psig

50. What is a common temperature difference between the condensing temperature on an air-cooled condensing unit and the outdoor ambient temperature...
20 to 30
An uninsulated TXV sensing bulb
Always have some liquid present in the bulb and diaphragm
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged