UNIT 41 REVIEW QUESTIONS ANSWER KEY GO BACK TO INDEX
41-1) List the four steps for isolating an electrical problem
1. Line voltage to the unit
3. Voltage to the nonfunctional component
41-2) What is often the first check made when nothing on the unit operates?
41-3) What checks should a technician make if a fuse to the system power supply has
blown?
41-4) List some things that can cause a system to lose its control voltage.
41-5) What ratings must be checked when replacing a fuse?
41-6) What is the normal control voltage for a residential air conditioner?
41-7) Discuss how a technician can differentiate between the “red” side of 24 volts
and the “common” side of 24 volts.
Most 24-volt control systems arrange the 24-volt control wiring so that one wire from the
41-8) What should the resistance of a closed (on) switch be?
41-9) How can the “B” terminal control connection cause a transformer
to fail?
41-10) What should the resistance of an open (off) switch be?
41-11) What should be checked whenever a low-voltage fuse is changed?
41-12) What should be the resistance of a load?
41-13) A technician sees that the contactor is closed and reads a voltage of 240 volts
across the contacts from L1 to T1. What does this indicate about the condition of
contactor contacts?
41-14) With the motor leads disconnected from the circuit, a technician reads 120
ohms between a motor lead and the motor frame. What does this indicate?
41-15) A technician reads a resistance of 540 ohms from the compressor start terminal
to the shell of the compressor. What does this indicate about the compressor?
41-16) When checking the resistance of a compressor, a technician reads OL on the
meter. What does this indicate about the compressor?
41-17) What procedure is used to isolate the break in a circuit?
41-18) Describe how to perform a hopscotching circuit check.
This technique works by starting at a point where there is correct voltage, and moving
41-19) Why is hopscotching more reliable than checking for voltage drop across each
switch in the circuit?
41-20) Which relay coil would have a higher resistance, a 24-volt relay coil or a 120-
volt relay coil?
41-21) A technician has determined that a motor is receiving the correct voltage but is
not operating. What should be checked next?
41-22) A technician reads 37 volts across a closed set of relay contacts on a 120 volt
circuit. What does this indicate about the relay?
41-23) When current passes through a load, the voltage should ____.
41-24) When current passes through a switch, the voltage should ____.
41-25) Why is adding a 3 amp fuse to the control circuit a good idea?
41-26) Which side of a transformer has a higher resistance?
41-27) Which side of the 24-volt control system is often grounded?
41-28) Describe what an electrical “daisy chain” is and where it is used.
41-29) Electrical components can be grouped into two large categories. Name the two
41-30) What type of electrical components are thermostats, pressure
controls, and overloads?