Screws showing hot on a dimmer switch.

I came across this yesterday and don’t know what to think about it. This is a dimmer switch the slides up and down and has the on/off switch on the bottom. The screws were hot to the touch.

The screws are painted white.

Any thoughts?

I also included a picture of what it can look like when the drywall is not cut out so heat and cooling can be supplied to a room. This was a 7 year old house.



Dimmer switches do run warm. However there may be too great of a load on that particular switch or the switch itself may be faulty. Either way IMHO it should be reported.

The dimmer switch will be hotter than others and the metal screws will conduct the heat more than the plastic might. With the info given I would wonder about correct wiring of the switch. What was the ambient temp and how long had the light been on? Did the wiring in the wall show up?

Are they really that hot?

At 129 F you would feel it as hot.

104 F(40 C) is the max on metal surfaces for equipment standards with no “Hot Surface” warning label present.

There may be nothing wrong here but more info is needed.

If they did not feel obviously HOT, I would not call it out.

An actual temperature measurement is in order if you really want to know.


Saw the same thing at my brother-in-laws house. Sliding dimmer was hot to touch. He said he wired it and “it’s fine, been like that for over a year” :roll:

I would call it out.

Most likely a 600W dimmer, what is total Watts it is powering?


Is there something wrong with it?

Sorry, I missed Kevins “hot to touch” comment(oops!) but an actual temp. measurement will tell what is needed.

I’ve got a small blister from the one at my B-I-L’s house. Hate to see that happen to a kid.

I’d love to see a data sheet or something about how hot they are actually supposed to get.

Since you qualified that you would not call it out if they did not feel obviously hot, why would you call it out (since they did feel hot)?


For Kevin and your BIL.

Check the dimming capacity of the switch and compare it to the actual load being controlled.

Perhaps in both cases the circuit is over lamped and not a switch defect.

In general, I wouldn’t think the manufacturer would designed something that would result in the screws being that hot (with proper installation and wiring of course). I’m actually going back to the house today so I’m planning on taking off the cover to see what readings I get today.

The temperature in the house was 68 degrees yesterday. I had the lights on high for about 20 minutes. This switch supplies power to 6 recess lights in the living room ceiling which are way to high to determine anything else. The buyer actually went to turn the lights off and felt one of the screws.

The good thing about this situation is one of the buyers father is an electrician.

I’ll post any new findings later on tonight when I get back.

Kevin, it may just need a higher wattage rated dimmer installed.

they run warm but running too hot and above ratings destroys them quickly.

600 watt dimmers are common but 1000 watt are available.

IMO, it’s too hot. Can’t predict time to failure or in this case, time to a fire.

What is the significants in this?

With infrared, bare metal can give you a wrong reading. With the Infrared camera, I’m actually reading the temperature of the paint that’s on the screw.

OK, good.

I don’t see many bare screws unless the cover plate is metal.

Ok, I went back and I had the same temperatures. Took the cover off but couldn’t see any wires unless I took the dimmer switch out (which I wasn’t going to do). I just reported what I seen and felt and did recommend further evaluation to determine if some type of correction is needed. Being able to feel that the screws are hot by itself is good enough for me to recommended further evaluation by an electrician.

Ok, I didn’t pay attention that you do infrared scanning. When I show problems descovered by an Infrared camera to others, the question seems to always comes up if I was scanning metal.:roll: If I didn’t include that information when starting this tread, there was a good chance somebody would have asked that question.

Kevin, I have come across this a lot.
Mostly it is high wattage on the circuit. Thoes can lights in this case.
There are many options on bulb wattage for can lights. Be sure someone didn’t over do it on one or more bulbs. No need for a high watt bulb that needs to be dimmed all the time!
Higher amp dimmer switches have heat sinks to handle the heat they make.
They won’t fit in your box though.
The screws are the heat sink conductor to the “outside”.
Just beware that they make a lot of heat as part of their job (like a GFCI outlet).
You will likely find the circuit breaker on this same circuit also hot at the panel. Not too hot, just quite hot! :slight_smile: