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I have 3 down lights in the bathroom. 2 burned out and as any other man I bough seemingly suitable replacement but other than fitting in the right place, doesn't work properly.

The burned out lights were of type : MR16 GU5.3 40W output.

First I bought the following replacement of the same type:LED MR16 4.5W (35W output). Replacing both lights resulted in:

  • Light 1 - working but starts flickering after a few minutes
  • Light 2 - does not turn on

At this point I am confused and go get another pack with different parameters: LED MR16 3W (25W output). This time:

  • Light 1 goes on for a fraction of the second and goes off (every switch)
  • Light 2 flickers constantly.

The only difference is that the original ones were Halogen, but I was under the impression that I can replace one with the other?

Has anyone got any suggestions as to what might be causing this and how to remedy it?


To answer some of the questions:

What are the specific lamps you got? Can you link to a product page, if nothing else?

https://www.amazon.co.uk/VINSUN%C2%AE-MR16-LED-bulbs-3W/dp/B00PUDPYGW/ref=sr_1_7?s=lighting&rps=1&ie=UTF8&qid=1526240028&sr=1-7&keywords=gu5.3+20w&refinements=p_76%3A419158031

These are 12V lights, right? Is there a dimmer function?

12V yes. No Dimmer functionality.

These MR16 type lights run on 12 V AC. That means the mains voltage (120 V or 240 V AC depending on your country) needs to be converted down to 12 V. Traditionally a transformer is used for that. There are also more modern (electronic / dimmable) "transformers" which might only work with the old style Halogen bulb based lamps. The new LED lamps consume considerably less power and that might confuse the electronic transformer and resulting in the behavior you get. Either use halogen bulbs only or replace everything with something that can work with the LED bulbs.

Not sure what the transformer in place is.

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  • 1
    It's possible you can operate with two LED bulbs and one halogen. – Spehro Pefhany May 13 '18 at 19:49
  • Too low load. +1 what Spehro said or replace the dimmer and/or transformer depending on which is causing the problem. – winny May 13 '18 at 20:36
  • Does it work with one halogen installed? Does the light switch have any other sort of "smart" or powered functionality, backlight, motion sensor, etc.? Are you handy enough to jumper each of the lights to a car battery or wall-wart 12VDC source, and see if it works on straight DC? – Harper May 13 '18 at 20:42
  • No smart features around the switch, and it works with just one light in place. – StanV May 14 '18 at 14:39

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