How to Replace a Thermocouple on a Recessed Light Fixture. If you have recessed lights in your home, you may notice that one or two of your lights may tend to turn off all by themselves. No, your house is not haunted; it may just be that the thermocouple inside the recessed light is heating up and causing the power to the light to be interrupted. Thermocouples are small, tubular fixtures that get wired between the line and the load of the recessed light, and when the heat builds up, they turn the light off to prevent damage to the wires. The temperature rise can be attributed to a bad thermocouple or your attic's insulation may have come too close to the light fixture. If you have already checked the insulation and it is about 6 inches clear of the light, then odds are the thermocouple needs to be replaced. Here is how to replace a bad thermocouple on a recessed light fixture.
You should easily be able to get a replacement thermocouple from your local electrical supply store, but make sure you get the right one; you should remove the old one first and take it with you when you purchase the new one.
Since you are going to be working overhead, be sure to wear eye protection. Of course, if you do not have a drop-in ceiling, you may have to get access to the recessed light's junction box through the attic.
As usual, before you begin working on the light, turn the circuit breaker that is supplying power to it OFF. It is not enough to simply turn the switch off, because anyone walking into the room can accidentally flip the switch out of habit, causing you to get a jolt! So be safe and turn the breaker OFF.
Remove the light bulb from the fixture and locate the fixture's junction box. On the side of the box you should see a tubular object about the size of a stick of lip balm. That is the thermocouple.
On the interior of the junction box you will see two wires coming off of the thermocouple. One is usually black and the other blue. One wire is connected to the feed circuit and the other is connected to the wire coming from the light socket. Disconnect each wire and screw the wire nut back on the feed wire and the socket wire respectively.
You should now be able to just snap the thermocouple out of the junction box. Take it to your local electrical supply store and pick up a replacement.
Once you return home, snap the new thermocouple back into the open knockout. Connect the black thermocouple wire to the feed wire and tighten it securely with a wire connector. Wrap the wires with a strip of electrical tape.
Connect the blue wire to the wire coming from the light socket. Secure them with a wire connector and tape them as well.
Replace the junction box cover and turn the circuit breaker back on. Screw the light bulb back in and turn the light switch back on. Now the light should no longer randomly blink on and off.