Test your basic knowledge |

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. If a TXV sensing bulb had lost its charge - what effect would this have on the air conditioning system...
Technician B
It would cause the low-side pressure to decrease
Bad compressor valve
110-120

2. 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...

3. The technician observes a pressure drop of 25 degrees across an air conditioning evaporator coil at start-up. This drop would indicate...
The superheat increases and the subcooling decreases
Partially frosted evaporator and high superheat
A plugged filter drier
Lack of airflow

4. When using a vapor-charged TXV bulb - it is necessary to have...
A dirty condenser - recirculation of condenser air - and a defective condenser fan
A plugged filter drier
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
The sensing bulb at a lower temperature than the valve body

5. 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
Technician B
Technician A is correct
Low discharge pressure - high suction pressure - and low amp draw
Both technicians are incorrect

6. 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
Condenser fans operating during a low ambient condition and a low suction pressure
An uninsulated TXV sensing bulb
The superheat increases and the subcooling decreases
Broken rings+broken valves+seized bearings

7. A hard-start kit for an air conditioning system...
Increases starting torque
Technician B
An increase in suction pressure and an increase in discharge pressure
A start capacitor and a solid-state relay

8. 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
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
Technician B
A bad thermostat
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure

9. What are the symptoms of a TXV air conditioning system if it has lost its charge...
A start relay
The superheat will increase and the low-side pressure will decrease
A dirty condenser - recirculation of condenser air - and a defective condenser fan
It would cause the low-side pressure to decrease

10. 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...
Short cycling and insufficient dehumidification
A dirty condenser - recirculation of condenser air - and a defective condenser fan
An increase of air leakage from ductwork
The internal overload is opened

11. A commercial customer calls on a 90
The system has been overcharged+The system has air trapped in the condenser
Low superheat
An open internal overload protector
'G' to 'C'

12. A restricted air filter in an air conditioning system can be identified by...
Clean the condenser coil
The system has been overcharged+The system has air trapped in the condenser
Evaporator and compressor
Low superheat

13. What are two common problems that can cause a sight glass in an air conditioning to have bubbles...
An uninsulated suction line and a restricted metering device
An undercharge and low ambient conditions
Technician B
An open internal overload protector

14. Which of the following can cause excessive subcooling...
Clean the condenser coil
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication
Technician B
An overcharged system

15. What type of problems can be caused by an oversized air conditioning system...
Short cycling and insufficient dehumidification
Bad compressor valve
The system has been overcharged+The system has air trapped in the condenser
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil

16. Why is it unsafe to operate an air conditioning system with a low charge...
110-120
Both technicians are correct
Lack of airflow
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication

17. 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
Technician A
Technician B
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor

18. A commercial customer calls on a 90
The system has been overcharged+The system has air trapped in the condenser
Low discharge pressure - high suction pressure - and low amp draw
The external equalizer could be plugged
A defective circuit breaker

19. 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...

20. When an air conditioning system has an undercharge - what happens to the superheat and the subcooling of the system...
The low-side pressure will decrease and the evaporator coil will be partially frosted
Low superheat
An overcharged system
The superheat increases and the subcooling decreases

21. What three things can prevent an air conditioning system from releasing heat at the proper rate...
The superheat will increase and the low-side pressure will decrease
A dirty condenser - recirculation of condenser air - and a defective condenser fan
Low voltage and a faulty start relay
The external equalizer could be plugged

22. 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
Bad compressor valve
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
An increase in low-side pressure

23. What is a common temperature difference between the condensing temperature on an air-cooled condensing unit and the outdoor ambient temperature...
20 to 30
A start relay
A vacuum test+oil traces around fittings+soap bubble solution
An undercharge and low ambient conditions

24. 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
Technician B
High superheat and low discharge pressure
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil
Current in the compressor circuit

25. Insufficient airflow can be caused by...
An undercharge and low ambient conditions
Whenever necessary
It keeps a constant superheat in the evaporator
An increase of air leakage from ductwork

26. 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
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
Both technicians are incorrect
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure

27. What problem or problems can cause low discharge and suction pressure...
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
An undercharged system+insufficient airflow over the evaporator coil
An overcharged system
Condenser fans operating during a low ambient condition and a low suction pressure

28. 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
An open internal overload protector
Current in the compressor circuit
Clean the condenser coil
Technician B

29. What controls are used on air conditioning or refrigeration systems that incorporate an automatic pump-down system...
The sight glass is full of liquid+the sight glass is full of gas
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil
An overcharged system

30. What is a possible cause of a sweat or frost pattern downstream from a sight glass and filter dryer...
'G' to 'C'
An uninsulated TXV sensing bulb
A plugged filter drier
An overcharged system

31. What are the operating pressures of an oil pressure safety switch...
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
The sight glass is full of liquid+the sight glass is full of gas
The oil pump pressure and the crankcase pressure
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor

32. What three things can prevent an air conditioning system from releasing heat at the proper rate...
The external equalizer could be plugged
A dirty condenser - recirculation of condenser air - and a defective condenser fan
Run with high head and high suction pressure
The low-side pressure will decrease and the evaporator coil will be partially frosted

33. 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...
Clean the condenser coil
20 to 30
Low voltage and a faulty start relay
The sensing bulb at a lower temperature than the valve body

34. An air conditioning unit has a suction line that is frosted up to the compressor. What faults could cause this to occur...
Technician B
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
Broken rings+broken valves+seized bearings
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay

35. 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
A restricted metering device
Lack of airflow
An uninsulated suction line and a restricted metering device

36. 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
The system has been overcharged+The system has air trapped in the condenser
A bad thermostat
The superheat will increase and the low-side pressure will decrease

37. 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
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
Flooding the condenser - cycling condenser fans - and dampering condenser air
The oil pump pressure and the crankcase pressure

38. What is a common discharge temperature of an air-cooled air conditioning system that is used on a 90
The oil pump pressure and the crankcase pressure
110-120
An uninsulated TXV sensing bulb
Whenever necessary

39. What is the purpose of an EPR valve...
Broken rings+broken valves+seized bearings
Broken rings+broken valves+seized bearings
Technician B
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system

40. 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
Technician B
Technician A
Dirty condenser - bent condenser fins - and air recirculating over the condenser
It is used to control refrigerant pressure in the compressor crankcase

41. Name two symptoms that are common to an over-charged air conditioning system and a system that has a dirty condenser.
Technician B
20 to 30
Both technicians are incorrect
The discharge pressure increases and the amperage increases

42. 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...
An undercharge and low ambient conditions
Low voltage and a faulty start relay
A blown fuse
An uninsulated TXV sensing bulb

43. The internal overload of an air conditioning compressor senses winding temperature and...
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil
The sight glass is full of liquid+the sight glass is full of gas
Current in the compressor circuit
An undercharged system+insufficient airflow over the evaporator coil

44. Superheat is found in an air conditioning system in the...
Evaporator and compressor
Run with high head and high suction pressure
The external equalizer could be plugged
Dirty condenser - bent condenser fins - and air recirculating over the condenser

45. What is the purpose of the TXV...
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
Technician B
It keeps a constant superheat in the evaporator
The superheat increases and the subcooling decreases

46. 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
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
An open internal overload protector
Always have some liquid present in the bulb and diaphragm
Technician B

47. 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
An overcharged system
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
The external equalizer could be plugged
Lack of airflow

48. 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...
Clean the condenser coil
Technician B
Current in the compressor circuit
The internal overload is opened

49. What problem or problems can cause the discharge pressure to be low and the suction pressure to be high...
Technician B
Condenser fans operating during a low ambient condition and a low suction pressure
Bad compressor valve
'G' to 'C'

50. 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
A restricted metering device
Lack of airflow
Both technicians are correct
Both technicians are incorrect