A window air conditioner has been unplugged from the wall and the technician is about to work around its start and run capacitors. What has to happen before those terminals are touched?
- AThe unit must be plugged in briefly so the capacitors can bleed off through the motor
Reapplying power to bleed a capacitor puts the technician back into a live circuit and does not reliably drain anything once the unit is switched off again.
- The capacitors must be discharged through a resistor, since they hold a charge unplugged
- CThe capacitors must be left overnight, which is the only reliable way to drain them
Time is not a reliable discharge method. Many capacitors have no bleed resistor at all, or a failed one, and can hold a dangerous charge for a very long time.
- DThe capacitors must be taken out of their brackets and stored terminal side down
Removing a charged capacitor means handling it by the case with live terminals exposed, which is more hazardous than discharging it in place.
Why B is correct
Capacitors retain a stored charge after power is removed, and nothing about unplugging the appliance drains them. Discharging deliberately through a resistor bleeds that energy away in a controlled manner without the arc flash and pitting that a direct short produces. It takes a few seconds and it is done before any terminal or wire on the capacitor is handled.
What this question is testing
This item tests basic electrical safety on the appliance side of small appliance work. It checks that you know stored energy remains after disconnection, and that you can identify the controlled discharge method rather than relying on time or on reapplying power.
On the job
Small appliance work is as much electrical as it is refrigeration, and the sealed system is often the last thing to be suspected. Start relays, overloads, run capacitors, thermostats, defrost timers and door switches account for most no cool calls on window units and refrigerators. The safe sequence is the same every time: unplug the appliance, verify it is dead, discharge the capacitors, then diagnose. Techs who have taken a capacitor discharge across the hand rarely need reminding, and it is worth carrying a purpose made discharge tool rather than improvising with a screwdriver.
Memory technique
Pulling the plug stops the supply. It does not empty the tank.
Exam tip
Unplugged does not mean de-energised where capacitors are involved. Discharge is a separate, deliberate step in the sequence.
Where to look it up
Capacitors hold a charge after the appliance is unplugged. Discharge them through a resistor before touching the terminals.