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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. 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
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
It keeps a constant superheat in the evaporator

2. What are two common symptoms of an overcharged air conditioning system that uses a capillary-tube-type metering device...
An increase in suction pressure and an increase in discharge pressure
Technician B
The superheat will increase and the low-side pressure will decrease
Low discharge pressure - high suction pressure - and low amp draw

3. An air conditioning system using a fixed-orifice metering device and with noncondensables in the system will cause...
Current in the compressor circuit
It keeps a constant superheat in the evaporator
A defective circuit breaker
Run with high head and high suction pressure

4. What is a common discharge temperature of an air-cooled air conditioning system that is used on a 90
The sensing bulb at a lower temperature than the valve body
110-120
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
Technician A is correct

5. What are the symptoms of an air conditioning system that has a bad compressor discharge valve...
Whenever necessary
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
Low discharge pressure - high suction pressure - and low amp draw
Technician B

6. Which of the following will cause excessive discharge pressures on an air conditioning system...
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
The external equalizer could be plugged
'G' to 'C'
Technician B

7. What is a possible cause of a sweat or frost pattern downstream from a sight glass and filter dryer...
The external equalizer could be plugged
Run with high head and high suction pressure
Technician A is correct
A plugged filter drier

8. 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
20 to 30
An uninsulated suction line and a restricted metering device
Clean the condenser coil

9. 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 superheat increases and the subcooling decreases
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device

10. Which of the following could be the cause for a system's discharge and suction pressure being low...
A restricted metering device
A plugged filter drier
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
A missing air filter+improper rotation of the indoor blower+blower too small

11. A hard-start kit consists of...
A start capacitor and a solid-state relay
3 psig
The discharge pressure increases and the amperage increases
Low superheat

12. 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 low-side pressure will decrease and the evaporator coil will be partially frosted
Technician B
The sensing bulb at a lower temperature than the valve body
An increase of air leakage from ductwork

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
Bad compressor valve
A blown fuse
50-65
A bad thermostat

14. Insufficient airflow can be caused by...
An increase in suction pressure and an increase in discharge pressure
An increase of air leakage from ductwork
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication
A restricted metering device

15. What is the purpose of the TXV...
An overcharged system
It keeps a constant superheat in the evaporator
Technician B
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil

16. The temperature range of the suction line from an air conditioning system should be...
An increase of air leakage from ductwork
Clean the condenser coil
Partially frosted evaporator and high superheat
50-65

17. Which of the following is a possible cause for a compressor to overheat...
Both technicians are incorrect
A low refrigerant charge
('Y' and 'C') and ('G' and 'C')
Short cycling and insufficient dehumidification

18. 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
Clean the condenser coil
Both technicians are incorrect
High superheat and low discharge pressure
The sensing bulb at a lower temperature than the valve body

19. 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
Technician A
An increase of air leakage from ductwork
The system has been overcharged+The system has air trapped in the condenser
Both technicians are incorrect

20. What causes the automatic expansion valve to close...
An increase in low-side pressure
Both technicians are incorrect
A start capacitor and a solid-state relay
'G' to 'C'

21. The internal overload of an air conditioning compressor senses winding temperature and...
3 psig
Technician B
Both technicians are incorrect
Current in the compressor circuit

22. When using a vapor-charged TXV bulb - it is necessary to have...
Clean the condenser coil
The sensing bulb at a lower temperature than the valve body
('Y' and 'C') and ('G' and 'C')
Both technicians are correct

23. Which of the following problems can cause a decrease in a system's pressures and possible icing of the evaporator coil...
A missing air filter+improper rotation of the indoor blower+blower too small
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
A start relay
Clean the condenser coil

24. What is the purpose of a CPR valve...
Bad compressor valve
It is used to control refrigerant pressure in the compressor crankcase
Technician B
Partially frosted evaporator and high superheat

25. Which of the following is a possible cause for a compressor to overheat...
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
A low refrigerant charge
Bad compressor valve
The sensing bulb at a lower temperature than the valve body

26. 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
An overcharged system
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device

27. What are the symptoms of an air conditioning system that has a low charge...
Low voltage and a faulty start relay
The low-side pressure will decrease and the evaporator coil will be partially frosted
A bad thermostat
Contains a solenoid coil and one or more sets of contacts

28. 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
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

29. 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...
3 psig
Technician B
An open internal overload protector
Low voltage and a faulty start relay

30. A split-system air conditioner that uses a piston-type metering device is to be charged with are-22. Technician A says that the outdoor dry-bulb temperature is needed to determine the proper superheat. Technician B says that the indoor wet-bulb tempe
Both technicians are correct
An increase in suction pressure and an increase in discharge pressure
It keeps a constant superheat in the evaporator
Increases starting torque

31. What is a common temperature difference between the condensing temperature on an air-cooled condensing unit and the outdoor ambient temperature...
It keeps a constant superheat in the evaporator
An acid-core suction line drier
The sensing bulb at a lower temperature than the valve body
20 to 30

32. 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...
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
A vacuum test+oil traces around fittings+soap bubble solution
The internal overload is opened
High suction pressure and low superheat

33. 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 dirty evaporator coil+a plugged air filter+a bad indoor blower relay
Both technicians are incorrect
The sight glass is full of liquid+the sight glass is full of gas
Rise more than normal

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 customer calls with an insufficient cooling complaint on a 90
Technician B
High superheat and low discharge pressure
It keeps a constant superheat in the evaporator
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor

36. A system that is operating with a clear sight glass shows...
The low-side pressure will decrease and the evaporator coil will be partially frosted
A sensing bulb improperly connected to the suction line
Both technicians are incorrect
The sight glass is full of liquid+the sight glass is full of gas

37. 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
Both technicians are incorrect
Technician B
Broken rings+broken valves+seized bearings
An overcharged system

38. A commercial customer calls complaining that her rooftop air conditioning system is not operating. The technician arrives on the job and sets the thermostat to cooling - then notices that the indoor fan is not operating. The technician then sets the

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39. What types of symptoms will be present if the sensing bulb of a TXV is not properly connected...
The sight glass is full of liquid+the sight glass is full of gas
A bad thermostat
An overcharged system
High suction pressure and low superheat

40. 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
A start capacitor and a solid-state relay
The system has been overcharged+The system has air trapped in the condenser
Technician B
The sensing bulb at a lower temperature than the valve body

41. 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
Technician A
Technician B
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication

42. 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
A start relay
It keeps a constant superheat in the evaporator
Partially frosted evaporator and high superheat

43. What are two problems that can cause an air conditioning system to have an excessively high superheat...
An uninsulated suction line and a restricted metering device
A blown fuse
It would cause the low-side pressure to decrease
A start relay

44. What three things can prevent an air conditioning system from absorbing heat at the proper rate...
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication
Dirty condenser - bent condenser fins - and air recirculating over the condenser
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil
A sensing bulb improperly connected to the suction line

45. A customer calls with an insufficient cooling complaint on a 90
Dirty condenser - bent condenser fins - and air recirculating over the condenser
Whenever necessary
Always have some liquid present in the bulb and diaphragm
Technician B

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
The discharge pressure increases and the amperage increases
The external equalizer could be plugged
Increases starting torque
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system

47. 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 sight glass is full of liquid+the sight glass is full of gas
An increase of air leakage from ductwork
A blown fuse
An open internal overload protector

48. A system that uses a thermal electric expansion valve...
An uninsulated TXV sensing bulb
An uninsulated TXV sensing bulb
The sight glass is full of liquid+the sight glass is full of gas
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system

49. The internal overload of an air conditioning compressor senses winding temperature and...
An increase of air leakage from ductwork
Current in the compressor circuit
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
High superheat and low discharge pressure

50. 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
Low voltage and a faulty start relay
Evaporator and compressor
It would cause the low-side pressure to decrease
Clean the condenser coil