Receptacles, switches, thermostats and low-voltage circuits

Receptacles, switches, lamps and low-voltage circuits — a thermostat, a doorbell, landscape lighting — together with the tests that show whether a fault is in the device or in the circuit behind it. Everything here stops at the last device on a circuit that already exists.

Common failure modes

• A device blamed for a fault that is in the circuit behind it
• A GFCI or RCD that has never been tested and no longer trips
• Thermostat wires pulled off and not labelled before removal
• A low-voltage transformer loaded past its rating
• A light fitting replaced when only the lamp had failed

Procedures

• How to tell if a surge protector still works, and when to replace a surge protector or power stripA surge protector is the power strip you bought because the box said surge protector, and the thing almost nobody is tol
• How do I know which LED bulb to buy? Reading lumens, watts equivalent, color temperature and bulb base size before you shopMost people still shop for a light bulb the way their parents did: by the watts printed on the old bulb. Watts measure t
• Match an extension cord to the appliance it will supplyAn undersized extension cord can overheat and catch fire, even though the appliance works normally. You will read three
• How to find out which outlets a GFCI protects, and why a dead bathroom or garage outlet is often a GFCI that tripped somewhere elseA GFCI receptacle is the outlet with the TEST and RESET buttons on its face, and it almost never protects only itself. C
• How to replace a thermostat and get the wires on the right terminalsSwapping a room thermostat is an afternoon of careful labelling wrapped around about ten minutes of actual work. The wir
• How to change landscape light bulbs and work out if my transformer can take themGarden lighting fails in a boring, predictable way: a lamp dies, someone puts in whatever was on the shelf, and three ye
• Set a heating and cooling schedule on a programmable thermostatA programmable or smart thermostat can hold a different target temperature at different times of day, so the heating or
• How to test a GFCI outlet with the TEST and RESET buttons, and what it means when it will not resetA GFCI receptacle is the outlet with the TEST and RESET buttons on its face, and it is usually the one in a bathroom, a

Where this stops

The service panel, the meter, any new or extended circuit, and any work that needs the supply isolated at the panel are never covered. A page on those topics gives you the diagnostic, tells you what to ask a licensed electrician, and stops there.