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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 commercial customer calls on a 90
Both technicians are incorrect
Whenever necessary
The system has been overcharged+The system has air trapped in the condenser
A start relay

2. 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
Whenever necessary
The system has been overcharged+The system has air trapped in the condenser
An increase in suction pressure and an increase in discharge pressure

3. 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...
Low voltage and a faulty start relay
Technician B
The internal overload is opened
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure

4. Which of the following is a possible cause for a compressor to overheat...
Increases starting torque
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
A low refrigerant charge
Technician A

5. What problem or problems can cause the discharge pressure to be low and the suction pressure to be high...
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
Bad compressor valve
Low voltage and a faulty start relay
Technician B

6. What are two problems that can cause an air conditioning system to have an excessively high superheat...
Both technicians are incorrect
Flooding the condenser - cycling condenser fans - and dampering condenser air
An uninsulated TXV sensing bulb
An uninsulated suction line and a restricted metering device

7. What are three methods for controlling a system's high-side pressure during low ambient conditions...
Flooding the condenser - cycling condenser fans - and dampering condenser air
The superheat will increase and the low-side pressure will decrease
Both technicians are incorrect
An acid-core suction line drier

8. Why is it unsafe to operate an air conditioning system with a low charge...
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication
An undercharged system+insufficient airflow over the evaporator coil
An acid-core suction line drier
Technician B

9. 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
Clean the condenser coil
Condenser fans operating during a low ambient condition and a low suction pressure
Lack of airflow

10. 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...
The system has been overcharged+The system has air trapped in the condenser
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication
Always have some liquid present in the bulb and diaphragm
Low voltage and a faulty start relay

11. What is a possible cause of a sweat or frost pattern downstream from a sight glass and filter dryer...
'G' to 'C'
An overcharged system
A plugged filter drier
It is used to control refrigerant pressure in the compressor crankcase

12. A compressor having tight bearings would cause the current value to...
Rise more than normal
An open internal overload protector
A dirty condenser - recirculation of condenser air - and a defective condenser fan
The low-side pressure will decrease and the evaporator coil will be partially frosted

13. Which of the following will cause excessive discharge pressures on an air conditioning system...
An undercharged system+insufficient airflow over the evaporator coil
A restricted metering device
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

14. 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
Always have some liquid present in the bulb and diaphragm
The low-side pressure will decrease and the evaporator coil will be partially frosted
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
Technician B

15. 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 internal overload is opened
20 to 30
Technician B
The external equalizer could be plugged

16. What problem can cause an increase of discharge pressure and an increase of suction pressure...
An overcharged system
20 to 30
A defective circuit breaker
Evaporator and compressor

17. What controls are used on air conditioning or refrigeration systems that incorporate an automatic pump-down system...
A start capacitor and a solid-state relay
Dirty condenser - bent condenser fins - and air recirculating over the condenser
The low-side pressure will decrease and the evaporator coil will be partially frosted
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor

18. What problem or problems can cause low discharge and suction pressure...
An undercharged system+insufficient airflow over the evaporator coil
High suction pressure and low superheat
Lack of airflow
Technician B

19. 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
Lack of airflow
Technician A
Both technicians are incorrect

20. On an are-22 air conditioning system - the suction-line filter drier should be changed when the pressure drop dictates...
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
3 psig
An overcharged system
The superheat will increase and the low-side pressure will decrease

21. What is a common temperature difference between the condensing temperature on an air-cooled condensing unit and the outdoor ambient temperature...
Rise more than normal
The sight glass is full of liquid+the sight glass is full of gas
Technician B
20 to 30

22. What are the symptoms of an air conditioning system that has a bad compressor discharge valve...
Low discharge pressure - high suction pressure - and low amp draw
Both technicians are incorrect
Condenser fans operating during a low ambient condition and a low suction pressure
The discharge pressure increases and the amperage increases

23. What are two common symptoms of refrigerant leaks in an air conditioning system...
The sight glass is full of liquid+the sight glass is full of gas
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
Partially frosted evaporator and high superheat
Bad compressor valve

24. A liquid-charged TXV bulb will...
Always have some liquid present in the bulb and diaphragm
Whenever necessary
An undercharge and low ambient conditions
The superheat increases and the subcooling decreases

25. 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...
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
('Y' and 'C') and ('G' and 'C')
A bad thermostat
A blown fuse

26. Which of the following is a common cause of an excessively low superheat on a TXV system...
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
110-120
A sensing bulb improperly connected to the suction line
An increase in low-side pressure

27. What three things can prevent an air conditioning system from absorbing heat at the proper rate...
The sensing bulb at a lower temperature than the valve body
An overcharged system
An open internal overload protector
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil

28. 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
The superheat increases and the subcooling decreases
Condenser fans operating during a low ambient condition and a low suction pressure
50-65

29. 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
Technician A
A sensing bulb improperly connected to the suction line
The low-side pressure will decrease and the evaporator coil will be partially frosted

30. 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
('Y' and 'C') and ('G' and 'C')
50-65
An uninsulated suction line and a restricted metering device

31. A customer calls and complains that his air conditioning system is not operating properly. It is noticed that the compressor is not operating. A check on the run capacitor shows that there is 33 uf and the rating on the capacitor is 40 uf. Technician
Both technicians are incorrect
An increase in suction pressure and an increase in discharge pressure
Technician B
An increase in low-side pressure

32. 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
The discharge pressure increases and the amperage increases
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
Short cycling and insufficient dehumidification

33. The technician observes a pressure drop of 25 degrees across an air conditioning evaporator coil at start-up. This drop would indicate...
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
Lack of airflow
An open internal overload protector
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication

34. Which of the following could be the cause for a system's discharge and suction pressure being low...
High suction pressure and low superheat
A restricted metering device
The sensing bulb at a lower temperature than the valve body
It would cause the low-side pressure to decrease

35. 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
Both technicians are correct
A start relay
A bad thermostat
An overcharged system

36. Which of the following can cause excessive subcooling...
The discharge pressure increases and the amperage increases
Run with high head and high suction pressure
Evaporator and compressor
An overcharged system

37. Insufficient airflow can be caused by...
An increase of air leakage from ductwork
A start capacitor and a solid-state relay
Condenser fans operating during a low ambient condition and a low suction pressure
The discharge pressure increases and the amperage increases

38. What problem or problems can cause the discharge pressure to be low and the suction pressure to be high...
Both technicians are correct
A dirty condenser - recirculation of condenser air - and a defective condenser fan
Clean the condenser coil
Bad compressor valve

39. Superheat is found in an air conditioning system in the...
Flooding the condenser - cycling condenser fans - and dampering condenser air
Evaporator and compressor
Technician B
Condenser fans operating during a low ambient condition and a low suction pressure

40. 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 defective circuit breaker
Technician B
The system has been overcharged+The system has air trapped in the condenser

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...
Rise more than normal
Current in the compressor circuit
The superheat increases and the subcooling decreases
Condenser fans operating during a low ambient condition and a low suction pressure

42. What are the symptoms of an air conditioning system that has a low charge...
The low-side pressure will decrease and the evaporator coil will be partially frosted
An increase in suction pressure and an increase in discharge pressure
Short cycling and insufficient dehumidification
The sensing bulb at a lower temperature than the valve body

43. Which of the following can cause low superheat in a TXV system...
An uninsulated TXV sensing bulb
Clean the condenser coil
3 psig
A vacuum test+oil traces around fittings+soap bubble solution

44. What causes the automatic expansion valve to close...
Contains a solenoid coil and one or more sets of contacts
Technician A
An increase in low-side pressure
A bad thermostat

45. 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
Contains a solenoid coil and one or more sets of contacts
Broken rings+broken valves+seized bearings
20 to 30

46. 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
An increase of air leakage from ductwork
Technician B
An undercharged system+insufficient airflow over the evaporator coil
An overcharged system

47. A restricted air filter in an air conditioning system can be identified by...
Low superheat
Lack of airflow
Technician B
An acid-core suction line drier

48. 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
An increase in suction pressure and an increase in discharge pressure
A missing air filter+improper rotation of the indoor blower+blower too small
Run with high head and high suction pressure

49. What are the symptoms of a TXV air conditioning system if it has lost its charge...
A restricted metering device
The superheat will increase and the low-side pressure will decrease
Low voltage and a faulty start relay
Condenser fans operating during a low ambient condition and a low suction pressure

50. 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
Technician B
20 to 30