What about Voltage
When troubleshooting split air conditioning systems be sure to check voltage to:
Both the indoor and outdoor unit
What should the resistance of a closed (on) switch be?
0
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?
The motor is grounded.
When current passes through a switch, the voltage should ____.
Stay the same
What ratings must be checked when replacing a fuse?
When replacing fuses make sure to match all of the fuse ratings including: voltage, amperage instantaneous current rating and class.
A method of measuring voltage across each component moving toward the malfunctioning load is called:
Hopscotching.
What should the resistance of an open (off) switch be?
OL or infinite ohms
When checking the resistance of a compressor, a technician reads OL on the meter. What does this indicate about the compressor?
An open motor.
Electrical components can be grouped into two large categories. Name the two categories.
Switches and loads
List some things that can cause a system to lose its control voltage.
Control voltage can be out because the part of the system that houses the transformer has no line voltage, because of an issue with the transformer that supplies the control voltage, or because of a blown 24-volt fuse.
What is the normal control voltage for a residential air conditioner?
24 volts
What should be the resistance of a load?
A good load will have a measurable resistance
Which relay coil would have a higher resistance, a 24-volt relay coil or a 120-volt relay coil?
A 120-volt relay coil would have a higher resistance than a 24-volt relay coil. Higher voltage goes with higher resistance
What type of electrical components are thermostats, pressure controls, and overloads?
controls or switches
What is often the first check made when nothing on the unit operates?
If the system does not operate at all, check to see that it has the correct line voltage
List the four steps for isolating an electrical problem
1. Line voltage to the unit
2. Control voltage
3. Voltage to the nonfunctional component
4. Circuit to the nonfunctional component
When there is high resistance across the contacts when they are closed:
A voltage drop will be read across the contacts
Which side of a transformer has a higher resistance?
The primary side
What procedure is used to isolate the break in a circuit?
The most effective method of locating a break in a circuit is a technique called hopscotching
Most circuits put all the controls on
One side of a load.
When current passes through a load, the voltage should
Drop
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?
The motor is shorted to the frame
The resistance of ________ can accurately be predicted using Ohm's law
resistors
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?
A voltage reading more than 0 volts but less than the full applied circuit voltage indicates bad electrical contacts in the switch.
The ________ is used to identify all the controls in series with the load.
electrical schematic