The old topic on this from a few years ago is closed, so I started a new one. This will help out a lot if you run across the same thing.
Older home, 1970's/80's Kitchen remodel, added 6 5" Halo cans, dimmer to old kitchen central light. When the customer would use their dimmer, the lights would literally strobe like a disco. They only worked on full brightness. No they aren't CFL's, normal incandescent 65 watt bulbs. 600 Watt Dimmer. So naturally, I figured it was just a bad dimmer. I change it out, all is fine until I leave, customer comes home, lights still doing it. So I head back the next day, two different style dimmers, one of the Lutron toggle/slides and one rotary old school style. Change the dimmer again, then my internal voice tells me "You need to know exactly why this is happening" since none of my friends had any idea why that was going on.
Ok, the set up is like this, an overhead tap on the old kitchen light, sends a dead end 14-2 to the first three way, 14-3 across the room to a 4 way switch, blacks tied through to a 14-3 to the other wall to a dead end three way... dimmer on the dead end three way.
I opened up every single box, pulled out all the wiring, nothing in the dead end wrong, nothing in the 4 way wrong, nothing in the overhead wrong, got to the first three way and noticed a couple wire nuts buried way in the back. First one was to the black tied into the line side for the box, second wire nut was a white wire tied into a ground wire.... jackpot. That new line feed coming out of the dead end 12-2 apparently back a few years back, some jackleg tried to pull power to a new light in the added on sun room. Once the brainiac discovered that they didn't have a neutral, they tied the sunroom light neutral in to the ground from the 3way kitchen circuit. Thus, energizing the ground, and sending varying voltages onto the grounding system and hitting the new dimmer, causing it to strobe out.
So, long story short, if you install a dimmer, and it's not CFL's, it's not an over rated dimmer, and your customer's lights are strobing like a disco, pull every tap in that circuit, look to see if some jackleg is using the ground as a current carrying conductor. That's what happened in this particular house.
Older home, 1970's/80's Kitchen remodel, added 6 5" Halo cans, dimmer to old kitchen central light. When the customer would use their dimmer, the lights would literally strobe like a disco. They only worked on full brightness. No they aren't CFL's, normal incandescent 65 watt bulbs. 600 Watt Dimmer. So naturally, I figured it was just a bad dimmer. I change it out, all is fine until I leave, customer comes home, lights still doing it. So I head back the next day, two different style dimmers, one of the Lutron toggle/slides and one rotary old school style. Change the dimmer again, then my internal voice tells me "You need to know exactly why this is happening" since none of my friends had any idea why that was going on.
Ok, the set up is like this, an overhead tap on the old kitchen light, sends a dead end 14-2 to the first three way, 14-3 across the room to a 4 way switch, blacks tied through to a 14-3 to the other wall to a dead end three way... dimmer on the dead end three way.
I opened up every single box, pulled out all the wiring, nothing in the dead end wrong, nothing in the 4 way wrong, nothing in the overhead wrong, got to the first three way and noticed a couple wire nuts buried way in the back. First one was to the black tied into the line side for the box, second wire nut was a white wire tied into a ground wire.... jackpot. That new line feed coming out of the dead end 12-2 apparently back a few years back, some jackleg tried to pull power to a new light in the added on sun room. Once the brainiac discovered that they didn't have a neutral, they tied the sunroom light neutral in to the ground from the 3way kitchen circuit. Thus, energizing the ground, and sending varying voltages onto the grounding system and hitting the new dimmer, causing it to strobe out.
So, long story short, if you install a dimmer, and it's not CFL's, it's not an over rated dimmer, and your customer's lights are strobing like a disco, pull every tap in that circuit, look to see if some jackleg is using the ground as a current carrying conductor. That's what happened in this particular house.
