Light Switches, Dimming Problem - Electrical - DIY Chatroom Home Improvement Forum

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Old 12-14-2008, 10:12 AM   #1
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Light switches, dimming problem

Recently bought a home, there are 3 - 3 way switches by the entry door:

Garage Inside Lights (8 std inc lights)
Garage Outside Lights (2 non-flood)
Entry hallway spot lights (4)

I've not been able to confirm yet but my suspicion is they are all on the same circuit. When one is on, they are fine, but if one is on and you switch on any one or both of the others they all dim.

Of course this has to be in the spot where it would take some good renovation to expose, re-do, and re-cover the wiring.

Any thing that could be done short of the re-wire? Any thoughts on potential mis-wired switches to cause it?




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Old 12-14-2008, 10:16 AM   #2
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You need to check for loose connections. For now, don't turn on more than one switch at a time. Loose connections get hotter the more current has to go through them and this is the cause of lots of house fires.

You'll need to (turn the power off and) open up each switch box and also any/all receptacle boxes along the way on that circuit going back to the breaker panel. If wires are pushed into a switch or receptacle and not held tight by a screw clamp , you should undo those and re-attach using screw terminals. Even the wire attached to the breaker and where the breaker clips on inside the breaker box should be tight and clean and you might as well check all the breakers except for the main breaker (you'll want a professional electrician to check that one).

You won't need to cut open the wall between electrical boxes, at least not while you look for and fix loose connections at first.


Last edited by AllanJ; 12-14-2008 at 10:21 AM.
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Old 12-14-2008, 10:22 AM   #3
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First place to look is in the switch box. Check for loose connections.

Second place to check is at the other switch box.

The wire may be making enough contact to let enough juice thru to operate a couple lights but when you increase the load, the electrons get all backed up trying to squeeze thru.

Many times you will find the faulty conection just by pulling out the switches. Other times it's not so easy and could be anywhere on the suply side. Turn the circuit off and make note of anything else on it. Try to determine a logical path from the panel to the switch boxes.

Problem could be in the black (supplying power) or the white (returning power).
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Old 12-14-2008, 11:48 AM   #4
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How many watts are the spots total? And how dim are we talking about? On a scale of 1-10, how dim? (1) is barely noticeable, and (10) is the extreme dimming seen from a movie electric chair.

I have seen 600 W of flood light on a long run of 14-2 cause lights to dim and stay that way until switched off. Maybe a (2). My point is, this may be a perfectly normal occurrence. So, you should check your connections, but don't be convinced there is one. If you overlook the possibility of this being natural, then you will spend countless hours of troubleshooting looking for a bad connection that isn't there!

On the other hand, it can be a bad connection, so it must be checked. Now, here's the complex part: a wiring mistake. A bad connection is often easy to spot, especially if you know what to look for. The harder job is identifying a problem that is due to a couple of crossed wires. Boxes get crowded and mistakes do happen. If you have three 3-ways in one box, there's likely at least 12 wires, then any number of other circuiting schemes can only add more. If the lights are very dim, it may be that a wire intended for one 3-way gets landed on another, then flipping the switch may be creating a series circuit with other lights, causing severe dimming.

Keep your eyes open.
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Old 12-14-2008, 01:04 PM   #5
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Thanks for the replies. I've never heard anything good about using the push-in connections and when I first moved in here found out why in the garage.

I plugged in a radio and then a drill at one point in the garage circuit. Every once in a while when I hit the drill the circuit would blow. When I checked the gfi and the breaker neither were popped.

I'd reset them both anyway, then it may work fine for a while, the pop again. Then I happened to notice that if I moved further up stream on the circuit stuff worked but the radio remained off.

I went along with a trouble light and plugged in each outlet top and bottom until I found that the bottom of one didn't work. Shut the power down, unscrewed it and sure enough, one of the push-ins came loose. You could see where it had been sparking against the metal.

12 wires - yup, have one 3-gang box, should be fun. I wouldn't doubt that the one outside outlet is somehow tied into all this too. I hope not.


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