Expert: Will Babbitt - 11/20/2007

Question
QUESTION: I recently installed a motion light for a friend.  He says it stays on very dim untill it senses motion and then it comes on bright.  Where should I begin with my trouble shooting?

ANSWER: First of all "motion sensors do not sense motion, but the heat generated by that motion.

There is not way I know to wire the detector in to come on dim, and the brighten up after i'ts sensor is tripped.

It could be there is a switch in the circuit, and if the ground and nuetral to the switch and then off to the detector were incorrect, maybe you would have that scenario.

Have a volt meter? Is this a completely new install or did you put a sensor in place of say a dusk dawn light or other existing fixture?

First of all, check two things, on the detector, SENSITIVITY, AND TIME.

IF THE SENSESITIVY adjustment is set too sensisitive, the light might come on part way, I doubt it though, I remember no detector that sensitivity would let the bulb come on low, or any other function.

Which leaves us with a low voltage situation to the detector, but if the bulbs come on correctly at dark, is sounds like that is not the problem either.

Tell me more about the install, new, old, exisiting, brand. switch controlled from a wall switch, temperature deviatins outside right now, of more than 15 degree swings.

When you write me, let me know what wires you used and where they came from, single circuit, anything you can and will figure this out.

ALSO ONE THING>

Before you do anything, remover all power from the detector for at least an hour, by BREAKER> No power to it all.
Then try it again.

Will

---------- FOLLOW-UP ----------

QUESTION: It is a new install.  I fed it from a circuit that feeds an attic light.  I changed the existing 12/2 to a 12/3 from switch to attic light and ran a 12/2 from attic light box approx fifty feet to light in back yard. so this light has no switch on it.

Answer
You took 50 feet of 12/2 to this motion light and it is tapped off a junction where an attic switch is?

Why did you change the attic wiring? From 12/2 to 12/3 and then wire this in?

I am trying to figure out if you were compensating for amps or what.

Two things, one get a volt meter and go measure the voltage at the 50 foot run.

Flip the attic switch while you are measuring [have someone do it] and see if it changes.

You either have some kind of volt drop or feedback through the attic switch or something is going on.

Can you temp wire just and old regular light in the motion detectors spot, and flip the attic switch to see what happens?

motion detectors are picky

Let me know all the above.

Will