Led floodlights and motion sensor compatibility

[2Broke2Sleep]

So I go on a service call to get some outside floodlights working. There are two hard wired dual head fixtures mounted on the wall of the residence. They have the motion/light sensor installed on each. Customer tells me one fixture wont come on and the other strobes. One fixture has halogens which are bad the other have LED floods installed. The LEDs strobe when the power is applied. I go through the circuit and buy replacement parts for what was out - the motion sensors and the two halogens.

After installing the new sensors and LEDs the one fixture with new LEDs works fine but the fixture with the existing LEDs (new sensor) is strobing again. I put new LEDs in their place which were SAME MAKE AND MODEL and voila it works all of a sudden!? Any explanations?

 

[2Broke2Sleep]

Didnt add this important piece: those existing LEDs worked fine when I put 120v to the shell

 

[gar]

180226-2429 EST

Use a motion sensor with an electromechanical relay that controls the light. When the motion sensor changes state you can hear the relay click.

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[2Broke2Sleep]

180226-2429 EST

Use a motion sensor with an electromechanical relay that controls the light. When the motion sensor changes state you can hear the relay click.

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My question is why does one pair of leds work in the fixture while the other flicker? Same make and model and they all work with 120v outside the fixture.....???

 

[GoldDigger]

My question is why does one pair of leds work in the fixture while the other flicker? Same make and model and they all work with 120v outside the fixture.....???

Even for the same make and model there can be differences over time or production batch or at random because of:

1. Deliberate changes in driver circuit design or manufacturing process that do not rise to the point of changing the model designation.
2. Changes in component values based on availability.
3. Variations in component specifications within their nominal tolerance range.

A motion sensor may be three wire type that has a neutral or EGC connection for power return (least likely to behave very differently with changes in exact load characteristics or the two wire type that depends on a circuit through the load to provide operating current to its electronics. These are very dependent on the current versus voltage curve of the load. Most robust with an incandescent lamp load, shakier with an electronic load, either LED or CFL.