Why is one of my LED downlights flashing? (once per second)

Discussion in 'Electricians' Talk' started by osullic, Feb 22, 2020.

  1. osullic

    osullic New Member

    I am renting a small flat that has about 20 downlights throughout the property. It looks like there's a random collection of whatever halogen downlights the previous tenants could find. Some are not working, so I'm replacing them all with new LED ones.

    I've just replaced the 8 in the kitchen/dining room. There are 2 light switches - 1 switch turns 5 bulbs on, the other turns the remaining 3 on. When I turn on the 3, one of them flashes, roughly once a second. I've tried 2 different brand new bulbs, and the behaviour is the same. All others turn on normally as expected. What could the cause of this be, and how can I fix it?

    For reference, the bulbs are all MR16 GU5.3 bulbs, 2.9W with 230 lumen output.
  2. MaxxHeadroom

    MaxxHeadroom New Member

    LED wifi ssmart bulb? Flashing once a second is usually the LED bulb in set-up mode to connect to the app?

    like this:
  3. osullic

    osullic New Member

    No, it is not any kind of "smart" app-connected bulb.
  4. osullic

    osullic New Member

    I have just tried again - turned the light switch on. No changes since last attempt an hour ago. Now there is no more flashing. I don't know what can have resolved the situation without any intervention.
  5. MaxxHeadroom

    MaxxHeadroom New Member

    How bizarre !?
  6. osullic

    osullic New Member

    And now... the flashing behaviour is back
  7. rogerk101

    rogerk101 Screwfix Select

    It's an incompatibility between the LED lamps and the driver.
    The only two brands of MR16 LED lamps that I find never flash with any drivers are from Philips and Osram.
    All others are somewhat hit and miss. Some flash, some flicker, some don't light at all, and some work perfectly.
    If you don't plan to change drivers, then your safest bet would be Philips or Osram LED lamps.
    Last edited: Feb 22, 2020
  8. DIYDave.

    DIYDave. Screwfix Select

    If you’ve got MR16’s, these are 12V so up in the ceiling will be a number of transformers

    Depends on rating of transformer and the original instal but could be 1 transformer for every light or could be 1 transformer for maybe 4 lights

    Thing is, these were originally running halogen lamps. To change to LED, for best performance you should ideally change all transformers to LED compatible

    Some halogen transformers will work with LED and others won’t, or will give random/poor performance and possible shortened lamp life

    If same lamp fitting is flashing, and you’ve tried another lamp in same fitting and it’s also flashing, likely that this one transformer is not happy with an LED lamp

    Several transformers could have failed over the years and been replaced one by one with various makes /types (they do fail fairly regularly with MR16s)

    Seems that this one doesn’t like LED

    With the power off at fuse board to lighting circuit, remove lamp and fitting from ceiling then gently pull on wires and hopefully will be a short length of flex with a transformer on the end

    Easy enough and cheap to replace if necessary

    If all others are working and uv swapped from halogen to LED lamps, then you’ve been lucky

    Although shortened lamp life could be an issue
  9. Bazza

    Bazza Screwfix Select

    The reliable method is to ditch the “MR16” lamps and the “transformers”. change the lot to 230volts GU10 LED lamps.

    If you have dimmers, you may need to change those to LED compatible ones too.
    seneca and rogerk101 like this.

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