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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 can cause excessive subcooling...
Current in the compressor circuit
Whenever necessary
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
An overcharged system

2. 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
A dirty condenser - recirculation of condenser air - and a defective condenser fan
A defective circuit breaker
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device

3. A commercial customer calls on a 90
The system has been overcharged+The system has air trapped in the condenser
Flooding the condenser - cycling condenser fans - and dampering condenser air
Partially frosted evaporator and high superheat
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser

4. 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 restricted metering device
Technician B
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
3 psig

5. A 220-volt 30-amp motor circuit keeps tripping the breaker after the motor is started. The starting amperage is 60 amps. When measuring the amperage of the circuit - This is drawn for a brief moment. After startup - the amperage drops to 22 amps and
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
A defective circuit breaker
Both technicians are incorrect
The superheat will increase and the low-side pressure will decrease

6. 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
A blown fuse
A start capacitor and a solid-state relay
An undercharge and low ambient conditions

7. What is the purpose of the TXV...
It keeps a constant superheat in the evaporator
A defective circuit breaker
110-120
Run with high head and high suction pressure

8. If a TXV sensing bulb had lost its charge - what effect would this have on the air conditioning system...
It would cause the low-side pressure to decrease
Always have some liquid present in the bulb and diaphragm
The system has been overcharged+The system has air trapped in the condenser
Technician B

9. 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
Low superheat
Current in the compressor circuit
It keeps a constant superheat in the evaporator

10. A system that uses a thermal electric expansion valve...
Lack of airflow
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
A vacuum test+oil traces around fittings+soap bubble solution

11. Name two symptoms that are common to an over-charged air conditioning system and a system that has a dirty condenser.
Technician B
The discharge pressure increases and the amperage increases
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
An overcharged system

12. What problem can cause an increase of discharge pressure and an increase of suction pressure...
Increases starting torque
50-65
A restricted metering device
An overcharged system

13. What causes the automatic expansion valve to close...
Technician A is correct
Technician A
'G' to 'C'
An increase in low-side pressure

14. 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...
Technician B
The internal overload is opened
An increase in low-side pressure
Clean the condenser coil

15. An air conditioning unit has a suction line that is frosted up to the compressor. What faults could cause this to occur...
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
High suction pressure and low superheat
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
An increase of air leakage from ductwork

16. 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
An overcharged system
Both technicians are incorrect
Contains a solenoid coil and one or more sets of contacts
High suction pressure and low superheat

17. Air filters should be replaced...
50-65
Whenever necessary
The external equalizer could be plugged
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged

18. If a TXV sensing bulb had lost its charge - what effect would this have on the air conditioning system...
An uninsulated TXV sensing bulb
It would cause the low-side pressure to decrease
An increase of air leakage from ductwork
The superheat increases and the subcooling decreases

19. A technician receives an air conditioning service call stating that the system is operating but isn't cooling properly. When the technician arrives - she notices that the compressor has recently been changed and it is an are-22 system. She checks the
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
A blown fuse
A bad thermostat
Condenser fans operating during a low ambient condition and a low suction pressure

20. A compressor having tight bearings would cause the current value to...
A vacuum test+oil traces around fittings+soap bubble solution
Rise more than normal
An overcharged system
High superheat and low discharge pressure

21. 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
Lack of airflow
Both technicians are incorrect
A bad thermostat
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser

22. 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...

23. What are two common symptoms of refrigerant leaks in an air conditioning system...
A blown fuse
Partially frosted evaporator and high superheat
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
An increase in suction pressure and an increase in discharge pressure

24. 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

25. What types of symptoms will be present if the sensing bulb of a TXV is not properly connected...
Lack of airflow
High suction pressure and low superheat
A restricted metering device
Both technicians are incorrect

26. What are possible problems that can cause the discharge-line temperature on an air conditioning system to be cool to the touch...
Technician B
Always have some liquid present in the bulb and diaphragm
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device

27. A rooftop package system keeps tripping out on the high-pressure switch. What are three possible causes for this problem...
Dirty condenser - bent condenser fins - and air recirculating over the condenser
Condenser fans operating during a low ambient condition and a low suction pressure
Low discharge pressure - high suction pressure - and low amp draw
An uninsulated suction line and a restricted metering device

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
Partially frosted evaporator and high superheat
Technician A is correct
Technician B
An open internal overload protector

29. 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
Bad compressor valve
An increase of air leakage from ductwork
Lack of airflow

30. 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
Lack of airflow
A missing air filter+improper rotation of the indoor blower+blower too small
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
Technician B

31. When an air conditioning system has an undercharge - what happens to the superheat and the subcooling of the system...
Low superheat
The superheat increases and the subcooling decreases
Dirty condenser - bent condenser fins - and air recirculating over the condenser
The sight glass is full of liquid+the sight glass is full of gas

32. Insufficient airflow can be caused by...
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil
A defective circuit breaker
High suction pressure and low superheat
An increase of air leakage from ductwork

33. What is the purpose of an EPR valve...
Contains a solenoid coil and one or more sets of contacts
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
Whenever necessary
The low-side pressure will decrease and the evaporator coil will be partially frosted

34. What are two problems that can cause an air conditioning system to have an excessively high superheat...
The external equalizer could be plugged
Bad compressor valve
An uninsulated suction line and a restricted metering device
An acid-core suction line drier

35. What controls are used on air conditioning or refrigeration systems that incorporate an automatic pump-down system...
A dirty condenser - recirculation of condenser air - and a defective condenser fan
A bad thermostat
Flooding the condenser - cycling condenser fans - and dampering condenser air
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor

36. 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
It is used to control refrigerant pressure in the compressor crankcase
20 to 30
The superheat will increase and the low-side pressure will decrease

37. What are the symptoms of an air conditioning system that has a low charge...
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
An open internal overload protector
Broken rings+broken valves+seized bearings
The low-side pressure will decrease and the evaporator coil will be partially frosted

38. Which of the following problems can cause a decrease in a system's pressures and possible icing of the evaporator coil...
The internal overload is opened
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser
Technician B
A missing air filter+improper rotation of the indoor blower+blower too small

39. 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
A dirty condenser - recirculation of condenser air - and a defective condenser fan
The superheat will increase and the low-side pressure will decrease
Technician A is correct
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system

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
Both technicians are correct
The oil pump pressure and the crankcase pressure
Technician B
A sensing bulb improperly connected to the suction line

41. 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...
Bad compressor valve
A blown fuse
The internal overload is opened
Partially frosted evaporator and high superheat

42. What is a common temperature difference between the condensing temperature on an air-cooled condensing unit and the outdoor ambient temperature...
Broken rings+broken valves+seized bearings
The sight glass is full of liquid+the sight glass is full of gas
A bad thermostat
20 to 30

43. A compressor having tight bearings would cause the current value to...
Rise more than normal
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
An uninsulated suction line and a restricted metering device
Technician A

44. 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 low-side pressure will decrease and the evaporator coil will be partially frosted
('Y' and 'C') and ('G' and 'C')
Low voltage and a faulty start relay

45. 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
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
Whenever necessary

46. What is a possible cause of a sweat or frost pattern downstream from a sight glass and filter dryer...
'G' to 'C'
Evaporator and compressor
110-120
A plugged filter drier

47. What causes the automatic expansion valve to close...
A low refrigerant charge
It keeps a constant superheat in the evaporator
An increase in low-side pressure
A low refrigerant charge

48. 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
High superheat and low discharge pressure
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil
Run with high head and high suction pressure

49. 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
Bad compressor valve
A defective circuit breaker
Technician B
It would cause the low-side pressure to decrease

50. 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
A vacuum test+oil traces around fittings+soap bubble solution
An undercharged system+insufficient airflow over the evaporator coil
An undercharge and low ambient conditions