Introduction: Motion Activated Light Switch Flicker Fix for CFL

If you've ever tried to add a motion activated light switch to a fixture with a CFL bulb you might have noticed that it flickers, unless you had the forethought to shell out 4 or 5 times as much for a dimmable  CFL.  

Typically the issue isn't with the motion detector or the CFL, but with the photoresistor light sensor bundled with the motion detector to keep the light off during the day.

Step 1: What's Being Removed

Here's a close up of the photoresistor from my model.  The photoresistor always has to be someplace in the motion detecting window to allow it to receive light.  I cut the leads long in case I need to create a short across the photoresistor instead of an open.

Step 2: View of the Circuit Board on the Back of the Switch With the Cover Removed.

A picture of the back of the motion detecting switch.

To fix the flicker the photoresistor needs to be removed.  A photoresistor has a high resistance in the dark and a lower resistance the brighter it gets. Opening the junction will simulate complete darkness and always allow the light to turn on using the motion detector.

I didn't have a pair of cutters small enough to get to the sensor, so I used a pair of regular scissors.

Step 3: Close Up of the Leads of the Photo Resistor

Make sure you have the motion detector facing up so when you cut the photoresistor it doesn't fall into the motion detector where you can't reach it.  You might also want to cut the leads long in case it doesn't work with an open circuit across the photoresistor and you need a short circuit instead.

Once you've cut the photoresistor out and turned off the circuit at the breaker install the switch and try it with a CFL before you close everything up into the wall.  If it works fine then you're all done.  

It really should work fine like this, but If not...

If the motion detection isn't working you can try creating a short across where the photoresistor was one of 2 ways.

1) Bend the 2 leads left by the photoresistor and very carefully solder them together being careful not to heat them too long as the leads can fall out once the original solder melts in the through hole.  I actually soldered in a short and it's been working fine for a week so far.

2) Try to solder a jumper across the more easily accessible side of the board.  If the leads were cut too short this might be your only option.