I have a GU10 light socket that is flickering. I bought a LED compatible outlet, quality LED dimmable bulbs (and have tried a few different ones). I suspect that the voltage is fluctuating because sometimes it works fine, and most of the time it flickers. I'm wondering what the voltage is coming out of the GU10 socket.

I cannot figure out how to test the voltage on this socket using my multimeter. Anyone have any bright ideas (pardon the pun)?

PS this switch is very simple, no indicator light or smart switching.

Edit: cannot use the multimeter because the metal prong doesn't seem to fit in very well.

  • Does it flicker when not dimmed ? Is the driver dimmable as well ? Jun 22, 2023 at 2:50
  • 2
    why is it you can not use multimeter
    – Traveler
    Jun 22, 2023 at 3:41
  • 1
    Did this used to have a halogen bulb in it? I've found that with new sockets the LED bulbs will work fine. With used halogen sockets I have to clean them for the LED bulb to work well, presumably because the halogen has cooked the contacts a bit.
    – KMJ
    Jun 22, 2023 at 5:44
  • Cannot use the multimeter because the metal prong doesn't seem to fit in very well. Yes, it does flicker even when at full power. But that is less surprising because sometimes the maximum voltage is too much for a bulb.
    – OhMyDIY
    Jun 23, 2023 at 13:34
  • Most multimeters have plugs for the leads to go into. You can replace the lead with a smaller one. You could even use just a bit of #12 or #14 wire (please be careful) if needed.
    – FreeMan
    Jun 23, 2023 at 16:53

2 Answers 2


I don't think that a multimeter is going to be of much help.

Possibilities -

  • Your mains voltage is fluctuating, you can try the bulb somewhere else in the house and see
  • The dimmer/switch on the wall is not compatible with the led driver
  • the driver is not compatible with the bulb
  • It is a cheap driver or a cheap bulb Post on Electrical Site The better one probably stays on and turns off slowly when switched off.

In my house, I have given up on dimmable LEDs and removed the dimming switches/knobs, which has stopped them from flickering. I have removed them for a dozen sets of lights, and a few more to go.

You may think that you have high-quality bulbs. I thought that I did as well, I paid a premium price to a reputable NZ supplier. But they have been a disappointment. I have between 6-8 bulbs (out of 100+) fail a year. Fortunately, the supplier has been replacing them (under warranty) for 5 years now.

  • OTOH, I've got some cheap-o LED bulbs (they came with the ceiling fan, ergo, they're cheap) and bog-standard LED compatible dimmers and have zero issue with flickering. I've also got some (relatively) inexpensive smart LED bulbs and have no flickering issues with those either.
    – FreeMan
    Jun 22, 2023 at 16:55
  • Good idea to try halogen or something.
    – OhMyDIY
    Jun 23, 2023 at 13:36

A way to triage the entire environment is to replace or parallel a pigtail light socket into the junction box where this fixture is located, and install a quality, known good regular A19 E26 (or whatever is regular in your country) light bulb. Binary search, left side is the light fixture, socket, and GU10 bulbs, right side is the switch, dimmer, cabling, supply.

  • Thanks for this idea, will give it a try! But do I really need to do that, can't I just voltage test at the switch? (Already a good idea that I'm grateful for)
    – OhMyDIY
    Jun 23, 2023 at 13:36
  • If you voltage test the entire running circuit, and even if you assume that your test equipment is capable of revealing whatever voltage fluctuations are occurring, which is slightly possible, you still won't have narrowed it down. IMO my approach is fast and easy, you have a reasonable (not guaranteed) chance of isolating the problem, and perhaps even fixing it but having isolated it, if you still want to use test equipment, it will be easier to understand any results you see.
    – jay613
    Jun 23, 2023 at 14:58
  • I'll try this another way. There's pretty high chances you have a bad dimmer or bulb or they're incompatible. There's pretty low chances you have mysterious "voltage fluctuations" and that your radio shack multimeter can detect and display them. :) A joke, I always regret making assumptions but people here. Maybe you have a recording oscilloscope. I don't know. I just think your time is best spent trying to identify the bad component you have.
    – jay613
    Jun 23, 2023 at 15:03

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