In one room of the apartment we rent, there's recessed 12v MR16 halogen lighting. There are 3 different circuits with dimmers.

I noticed that two of the bulbs were humming loudly even when dimmed all the way up. One light was constantly going off and on and flickering.

I took a closer look and I saw that the connections between the incoming 12v wires and the short wires going to the socket were in bad shape. Those connections were apparently made using wire nuts, and the plastic from the nuts had melted away completely. On one lamp, there was no plastic left at all, the naked wires enclosed by the wire nuts' metal spirals were sticking out. On the other lamp, one wire looked the same, and on the other one half a plastic cover was left. See the photos.

What's the proper, heat-safe way to connect the wires in this case? There's not much room in there, see the fourth photo below. I usually use WAGO lever connectors instead of wire nuts when I connect something and I was going to do the same here when I re-do the connections, but I'm not sure they'll perform any better in heat.

I'm also investigating replacing the halogen bulbs with LED ones anyway, so there might be a bit less heat in the future (BTW, any tips for MR12 LED bulbs?).

How is this usually done? I imagine there is often a need to connect the incoming wires in close proximity to the (hot) bulb in ceiling installations like this?

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    You should probably have used a high temperature twist-on wire connector, these specific ones are rated for 150°C (302°F). Or you could use ceramic twist-on wire connectors, which are rated for up to 1000˚F.
    – Tester101
    Mar 10, 2014 at 10:13
  • Thanks @Tester101, I'll look into those. Just to be clear, I didn't install the existing ones, they were there when we moved in. Mar 10, 2014 at 14:33
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    Also, read the UL sticker in the fixture to make sure it's listed for use with halogen bulbs.
    – Tester101
    Mar 10, 2014 at 14:44
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    Halogen lighting = intense heat. There's a reason the sockets are made of ceramic and any wire connector near them must be of the same materials or you get the expected results which is what you have experienced. Fiberglass or high temp woven ceramic insulated wires usually are never spliced inside the fixture, but extend out to a lower temperature area where there is little heat. I kind of question why these are done this way. Mar 10, 2014 at 15:02
  • Thanks again @Tester101 and Fiasco Labs. I ordered these ceramic nuts: amazon.com/gp/product/B0071NCTYY Mar 11, 2014 at 3:13

1 Answer 1


Thanks to Tester101's comment on my question I learned about ceramic high temperature wire nuts. I ended up using these: http://www.amazon.com/dp/B0071NCSA4, for 18-14 gauge wire (the ones noted in my comment above were too large, they are for 12-10 gauge wire and didn't hold on to the wires properly).

I read somewhere that halogen lights reach temperatures above 300°C, so the plastic high temperature wire nuts mentioned above are not an option as they are only rated up to 150°C. The WAGO nuts I intended to use were also not appropriate as they are only rated up to 105°C.

While I was already in there, I also replaced the lamp holders with these: http://www.amazon.com/dp/B0055D2Y2E because the metal contacts in the existing ones were corroded.

The result looks like shown below and it works great, no more flickering or humming.

I have to say that these ceramic nuts are a bit iffy to install, probably because they don't have the metal coil inside like the regular plastic wire nuts do. In one instance I twisted too much, and the nut just cut off the wires completely. Another nut never got a good grip on the wires and fell off, so I had to toss it and use another one from the same batch. If somebody knows of a better type of high heat nut, perhaps one that does have the metal coil inside, feel free to comment.

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