How do i install a Lutron TG-603PH toggler swith

SOURCE: Hello - I have just

Double check the model number - is it a TG-600PH or a TG-603PH?

If its a TG-603PH, and this is part of a 3-way circuit (there's another light switch that turns the lights those same lights on & off), then this is normal. If you flick the other light switch, you'll then see that the dimmer works like it should. This has always been the case with 3-way switches, up doesn't necessarily mean "on" and vice-versa.

If its a TG-603PH, and this is part of a single-pole circuit (this is the only light switch for those lights), then the product is miswired, and upside-down. To fix the miswire, look at the screws on the back of the unit (ignore the green grounding screw for the time being), two of those screws are made of the same material (same color), and only one of them should have an electrical wire going to it. Take that wire out and put it on the other screw of the same color. That fixes the miswire. Then when you re-install the device, flip it upside-down from what it was before.

If its DEFINATELY a single-pole, TG-600PH, then call their tech support center at 1-800-523-9466 - because that makes absolutely no sense.

Good luck!