Deck 22: Electrical Troubleshooting

Question 1

When checking a relay coil with an ohmmeter, an open coil would read __________ ohms.

A) infinite
B) 0
C) 100
D) 1000

Answer 1

A

Question 2

Low- and high-pressure controls are physically located on which piece of equipment?

A) condensing unit
B) air handler
C) either a or b
D) neither a nor b

Answer 2

A

Question 3

Which component on the low-voltage circuit of a residential HVAC system is NOT a switch?

A) thermostat contacts
B) high-pressure control
C) fan relay coil
D) fan relay contacts

Answer 3

C

Question 4

When an air conditioning system has been pumped down, which component is not isolated?

A) evaporator
B) filter/drier
C) TXV
D) compressor

Question 5

When diagnosing the control circuit on the thermostat subbase, between which two terminals would a jumper wire be placed to check the fan circuit?

A) R and G
B) R and W
C) R and Y
D) G and Y

Question 6

A high-pressure control closes on a pressure drop.

Question 7

When checking a fuse on a 24-volt power supply with a voltmeter, if the fuse is blown, __________ volts will be read across the fuse.

A) 0
B) 24
C) 48
D) 115

Question 8

When checking the secondary of a low-voltage transformer with an ohmmeter, if the transformer secondary is open it will read __________ ohms.

A) infinite
B) 0
C) 100
D) 1000

Question 9

When troubleshooting a residential air conditioning system, the technician turns the fan switch to ON and nothing happens. What is the most likely problem?

A) defective subbase
B) defective fan motor
C) defective fan control
D) any of the above

Question 10

When diagnosing the control circuit at the thermostat subbase, between which two terminals would a jumper wire be placed to check operation of the cooling circuit?

A) R and G
B) R and W
C) R and Y
D) G and Y

Question 11

When checking a relay coil with an ohmmeter, the coil will read __________ ohms if the coil is shorted.

A) infinite
B) 0
C) 100
D) 1000

Question 12

Which component on the low-voltage circuit of a residential HVAC system is NOT a load?

A) heat anticipator
B) thermostat contacts
C) fan relay coil
D) low-pressure control

Question 13

Many older thermostats contain mercury, so the technician must be sure to dispose of them properly.

Question 14

A low-pressure control closes on pressure drop.

Question 15

While troubleshooting a residential air conditioning system, the technician reads 24 volts across the compressor contactor coil, but the contactor does not energize. What is the most likely problem?

A) defective transformer
B) defective contactor contacts
C) defective contactor coil
D) high-voltage fuse blown

Question 16

When diagnosing the control circuit at the thermostat subbase, between which two terminals would a jumper wire be placed to check the heating circuit?

A) R and G
B) R and W
C) R and Y
D) G and Y

Question 17

How many amps should a low-voltage fuse be rated for to protect the secondary of a low-voltage transformer used in a residential HVAC system?

A) 1
B) 3
C) 5
D) 7

Question 18

Low- and high-pressure controls are typically located on the __________-voltage side of the circuit.

A) low
B) high
C) either a or b
D) neither a nor b

Question 19

When pumping down a residential central air conditioning system, which valve should be front seated?

A) liquid line
B) discharge line
C) suction line
D) all of the above

Question 20

If a low-pressure switch has opened on a residential air conditioning system, it is usually an indication of a defective low-pressure control.

Question 21

When troubleshooting a residential air conditioning system, the technician reads 24 volts across the high-pressure control. What would be the most likely problem?

A) defective high-pressure control
B) dirty condenser
C) defective compressor
D) defective transformer

Question 22

When troubleshooting a residential heating system, the technician reads 24 volts at the gas valve on a call for heat, but the gas valve does not energize. What would be the most likely problem?

A) defective gas valve
B) defective thermostat
C) defective transformer
D) blown low-voltage fuse

Question 23

List the four components that make up an electrical circuit.

Question 24

When troubleshooting a residential heating system, the technician reads 24 volts across R and W on the furnace low-voltage terminal strip with the thermostat set to call for heating. What would be the most likely problem?

A) defective gas valve
B) defective transformer
C) blown high-voltage fuse
D) defective thermostat

Question 25

List four conclusions that can be made about a residential HVAC system when the fan switch is turned to "ON" and the fan motor starts.

Question 26

When troubleshooting a residential air conditioning system, the technician notices the condenser fan motor operating, but the compressor is not. What is the most likely cause?

A) high-voltage circuit breaker for condensing unit is tripped
B) high-pressure switch is open
C) defective compressor
D) defective contactor