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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 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
Partially frosted evaporator and high superheat
The superheat increases and the subcooling decreases
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
An open internal overload protector

2. What are the symptoms of a TXV air conditioning system if it has lost its charge...
Clean the condenser coil
The superheat will increase and the low-side pressure will decrease
An increase of air leakage from ductwork
An increase in low-side pressure

3. What controls are used on air conditioning or refrigeration systems that incorporate an automatic pump-down system...
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
Condenser fans operating during a low ambient condition and a low suction pressure
An uninsulated suction line and a restricted metering device
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure

4. What is the purpose of the TXV...
The superheat increases and the subcooling decreases
Condenser fans operating during a low ambient condition and a low suction pressure
It keeps a constant superheat in the evaporator
The oil pump pressure and the crankcase pressure

5. 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
An open internal overload protector
The low-side pressure will decrease and the evaporator coil will be partially frosted
Lack of airflow
Technician B

6. What is the common cause of a compressor burnout...
An uninsulated suction line and a restricted metering device
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser
Technician B
An overcharged system

7. A liquid-charged TXV bulb will...
A blown fuse
An open internal overload protector
Always have some liquid present in the bulb and diaphragm
The superheat will increase and the low-side pressure will decrease

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

9. When a high-efficiency split air conditioning system has a plugged metering device - what symptoms might occur...
A start relay
Flooding the condenser - cycling condenser fans - and dampering condenser air
Condenser fans operating during a low ambient condition and a low suction pressure
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure

10. What are the symptoms of an air conditioning system that has a bad compressor discharge valve...
Rise more than normal
An overcharged system
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication
Low discharge pressure - high suction pressure - and low amp draw

11. 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
It is used to control refrigerant pressure in the compressor crankcase
Dirty condenser - bent condenser fins - and air recirculating over the condenser
Technician A is correct
Both technicians are incorrect

12. A system that uses a thermal electric expansion valve...
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
Clean the condenser coil
A start relay

13. What three things can prevent an air conditioning system from releasing heat at the proper rate...
A dirty condenser - recirculation of condenser air - and a defective condenser fan
A defective circuit breaker
Short cycling and insufficient dehumidification
('Y' and 'C') and ('G' and 'C')

14. 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
Condenser fans operating during a low ambient condition and a low suction pressure
A vacuum test+oil traces around fittings+soap bubble solution
Rise more than normal
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged

15. The technician observes a pressure drop of 25 degrees across an air conditioning evaporator coil at start-up. This drop would indicate...
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
Rise more than normal
Lack of airflow
High suction pressure and low superheat

16. 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
Always have some liquid present in the bulb and diaphragm
The sensing bulb at a lower temperature than the valve body
Technician B

17. Which of the following problems can cause a decrease in a system's pressures and possible icing of the evaporator coil...
'G' to 'C'
Technician B
A missing air filter+improper rotation of the indoor blower+blower too small
A low refrigerant charge

18. A compressor having tight bearings would cause the current value to...
Dirty condenser - bent condenser fins - and air recirculating over the condenser
An increase in low-side pressure
Technician B
Rise more than normal

19. What are two common problems that can cause a sight glass in an air conditioning to have bubbles...
Broken rings+broken valves+seized bearings
Technician B
An undercharge and low ambient conditions
A blown fuse

20. 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...
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser
The low-side pressure will decrease and the evaporator coil will be partially frosted
20 to 30
The internal overload is opened

21. 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
Current in the compressor circuit
Rise more than normal
Technician B

22. A customer calls with an insufficient cooling complaint on a 90
Low voltage and a faulty start relay
Technician B
('Y' and 'C') and ('G' and 'C')
Flooding the condenser - cycling condenser fans - and dampering condenser air

23. 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...
Low voltage and a faulty start relay
Technician B
It would cause the low-side pressure to decrease
Both technicians are correct

24. 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
A bad thermostat
An increase of air leakage from ductwork
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system

25. When an air conditioning system has an undercharge - what happens to the superheat and the subcooling of the system...
110-120
A missing air filter+improper rotation of the indoor blower+blower too small
An acid-core suction line drier
The superheat increases and the subcooling decreases

26. What three things can prevent an air conditioning system from absorbing heat at the proper rate...
Bad compressor valve
An overcharged system
Low discharge pressure - high suction pressure - and low amp draw
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil

27. 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
Clean the condenser coil
The sensing bulb at a lower temperature than the valve body
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
The low-side pressure will decrease and the evaporator coil will be partially frosted

28. Name two symptoms that are common to an over-charged air conditioning system and a system that has a dirty condenser.
Technician B
The external equalizer could be plugged
A restricted metering device
The discharge pressure increases and the amperage increases

29. What is a possible cause of a sweat or frost pattern downstream from a sight glass and filter dryer...
Technician B
A start relay
A plugged filter drier
Both technicians are incorrect

30. Name two symptoms that are common to an over-charged air conditioning system and a system that has a dirty condenser.
50-65
A blown fuse
An increase of air leakage from ductwork
The discharge pressure increases and the amperage increases

31. What is the common cause of a compressor burnout...
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
Dirty condenser - bent condenser fins - and air recirculating over the condenser
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser
Whenever necessary

32. 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
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
Technician A
Technician B
The external equalizer could be plugged

33. Which of the following problems can cause a decrease in a system's pressures and possible icing of the evaporator coil...
A defective circuit breaker
A restricted metering device
The superheat will increase and the low-side pressure will decrease
A missing air filter+improper rotation of the indoor blower+blower too small

34. What is the purpose of an EPR valve...
Condenser fans operating during a low ambient condition and a low suction pressure
Technician B
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system

35. 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
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil
Technician B
A vacuum test+oil traces around fittings+soap bubble solution

36. What are possible problems that can cause the discharge-line temperature on an air conditioning system to be cool to the touch...
The oil pump pressure and the crankcase pressure
It keeps a constant superheat in the evaporator
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil

37. What three things can prevent an air conditioning system from absorbing heat at the proper rate...
'G' to 'C'
The sight glass is full of liquid+the sight glass is full of gas
A bad thermostat
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil

38. What types of symptoms will be present if the sensing bulb of a TXV is not properly connected...
Lack of airflow
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
Technician A is correct
High suction pressure and low superheat

39. Insufficient airflow can be caused by...
An overcharged system
An increase of air leakage from ductwork
Technician A is correct
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure

40. When using a vapor-charged TXV bulb - it is necessary to have...
The sensing bulb at a lower temperature than the valve body
A restricted metering device
20 to 30
High superheat and low discharge pressure

41. Why is it unsafe to operate an air conditioning system with a low charge...
An increase in suction pressure and an increase in discharge pressure
A bad thermostat
Flooding the condenser - cycling condenser fans - and dampering condenser air
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication

42. What is the purpose of a CPR valve...
The sight glass is full of liquid+the sight glass is full of gas
It is used to control refrigerant pressure in the compressor crankcase
An overcharged system
The superheat increases and the subcooling decreases

43. The best description of a relay would be...
('Y' and 'C') and ('G' and 'C')
An increase in suction pressure and an increase in discharge pressure
Contains a solenoid coil and one or more sets of contacts
Technician A

44. What type of problems can be caused by an oversized air conditioning system...
Whenever necessary
3 psig
Increases starting torque
Short cycling and insufficient dehumidification

45. What types of symptoms will be present if the sensing bulb of a TXV is not properly connected...
High suction pressure and low superheat
Technician B
The sight glass is full of liquid+the sight glass is full of gas
A blown fuse

46. What are two common symptoms of an overcharged air conditioning system that uses a capillary-tube-type metering device...
Both technicians are incorrect
An increase in suction pressure and an increase in discharge pressure
Both technicians are correct
A start relay

47. 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
A defective circuit breaker
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
Run with high head and high suction pressure
Technician B

48. If a rooftop air conditioning system does not have any means of low ambient protection - what will be two symptoms of the system when operating under a low ambient condition...
High superheat and low discharge pressure
The low-side pressure will decrease and the evaporator coil will be partially frosted
An increase of air leakage from ductwork
Run with high head and high suction pressure

49. An air conditioning system using a fixed-orifice metering device and with noncondensables in the system will cause...
3 psig
Technician A is correct
Run with high head and high suction pressure
The external equalizer could be plugged

50. 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...
Low voltage and a faulty start relay
A plugged filter drier
A sensing bulb improperly connected to the suction line
A blown fuse