Why would a switch read 0 volts when the light is turned on and 120 volts when the light is turned off its actually quite simple. This occurrence is not a problem or fault of the light fixture in fact it is a great safety feature that prevents the light fixture from over heating which could possibly.
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How Does A Light Switch Work
Light comes on when switch is off. 3 the reason the light remains on is that the light is permanently connected to another hot wire in the ceiling. What you are measuring is a floating voltage. This is especially true with light fixtures that use incandescent light bulbs. When we turn the circuit breaker on the light comes on but when we try to turn the light off at the switch the circuit breaker trips. Turn the switch on then touch the tester leads to both of the brass terminals on the switch and verify that the tester led goes on. Turn the switch off then repeat the test.
One thing i probably should of mentioned is that the switch is part of a block of 4 with the other switches the right way round. What is happening is the recessed can lights have a high temp safety switch mounted into the top of the enclosure which will turn the light off if it gets too hot. In order for the light to work with the switch the ceiling light needs to be connected to the switched leg conductor coming off of the switch. For anybody that comes here in the future looking for help after replacing an electrical outlet that is supposed to be controlled by a light switch only to find the switch does not turn off the. If the led goes off the switch is good and the wiring is faulty but if the led stays on the switch is bad and needs to be replaced. The problem switch is on the left handside dining room switch mid left for the new fitting that works hall light is mid right switch and upstairs landing light righthandside the landing light is two way with.
The light fixture then cools down and after a few minutes it will come back on. Let say you have line hot going into a light bulb and the switch is connecting to the neutral side of the light bulb.
Gallery of Light Comes On When Switch Is Off
