Weird LED bulb issues on exterior garage coach lights

[JCROCCO]

I have 4 couch lights all circuited to the same switch, 1 at the front door, and 3 at the garage doors.
When I go to put LED bulbs intot the garage coach lights, only 2 work at a time, I cant get all 3 to come on.
doesnt seem to matter which 2 are on. I can move them around and only 2 come on at a time.
If I install a third bulb, but use a CFL, then all 3 work, again, no matter the order.
Why cant I get 3 LED bulbs to work? I have tried this with various LED bulbs and Manufacturers.
Is it a wiring Issues? Works absolutely fine with incandescents or CFLs in all 4, no issues.

 

[herm0016]

is there a dimmer or a dusk sensor in the circuit? or in the light fixtures themselves?

have you used a multimeter to check the voltage in the dead socket when you have 2 screwed in?

does the brightness change on the single when you screw in the second bulb?

does the behavior happen all the time or just at night?

evidence: dimmers and dusk sensors can do some really strange things when they are built for the resistance of incandescent lamps vs the capacitance they "see" on the load side of LED driver circuits.

when you have 2 lit and screw in the third, there may be enough light around ( if you are doing this at night) for the sensor in the 3rd fixture to trip to day and turn the socket off.

I also recently replaced 2 native LED fixtures for a client that were lighting maybe 50% when the dusk sensor was in an "on" state. i replaced the sensor, checked the wiring and it was some strange failure mode in the driver circuits of BOTH fixtures. very odd behavior. the original sensor was fine. replaced with fixtures that take a bulb, put in Led bulbs and they work great.

my porch lights that had dusk sensors in them would flash from a dim mode to a bright mode in some weird ghostly cycle with LED bulbs. like one would flash on, the next one sees too much light, goes dimmer, then the 3rd changes state, etc. it was very odd. they were old and made for incandescent bulbs.

leds are such low current that the sensors transistors can't latch and stay latched or they leak enough current to light the bulbs in an off or dimmed state.

had a thought about the 2/3 thing. maybe there is enough leakage current to light 2 lamps and not 3, or its sense threshold is broken by the 3rd lamp.

 

[JCROCCO]

Yes, the 4 fixtures are wired to a single pole switch, that I have replaced with a timer switch. I am not using the timer option any longer, as now I have the coach lights with light sensors and dimmers. when its bright enough out, the lights are off. when it gets dark they go on at 100% then after X time, go dim 50%. So I take it the light fixture itself is to blame. The first one installed doesnt dim when the second or third is installed. the second comes on at same brightness, when third is installed, it just doesnt go on at all.
If I want to use coach lights with LED builbs, do I need to buy them that way? Seems they all have Medium base type sockets for retrofits.

 

[herm0016]

it sounds like it's the fixtures to me. if you are into smart home stuff, you can use a wemo switch or equivalent and just program it to do whatever you want. wemo has a dusk to dawn that adjusts to your local sun set/rise time. I find it better with a bunch in the same area to wire in one sensor for the whole bank, so they cant interfere with each other. this also makes one failure point with a cheap to replace sensor, instead of a bunch of fixtures all with electronics in them. i'm sure new fixtures with sensors should work with Leds, but I would make sure it says they do on the box.