Electrical Question

Bulbs in bathroom go out after 20mins then come back on about 5 mins later

Some time ago I had an electrician do some minor work in my house and this included changing the bulbs in my bathroom lights as they had gone. Since being changed they all go out after about 20 mins and come back on again 5 mins later. The bulbs are MR16 50w 12v. I spoke to the electrician and he basically said if he came back out to look at them there would be a charge so I have lived with it as they are. They never did this before he changed them and now I finally want to find out why and get the problem sorted as I will be selling my house at some point in the future. I changed the bulbs myself today (finally figured out how to do it) and they are still doing it. What could be causing this? Thanks

4 Answers

Best Answer

The problem you have is as been highlighted in the other posts the transformer is overheating and cutting out, then as it cools down it resets and the lights come back on again.

Its likely that when the lights were new they had either MR16 20watt or MR16 35watt lamps in them. Because they have been replaced for higher wattage lamps (i.e. 50w ones) they are drawing more current and this is causing the transformer to work harder and hence why its overheating and cutting out.

Easily fixed buy some 20watt lamps for a few pounds, pop them in and an the problem should dissapear.

The guy who fitted the 50watt lamps should have only put the same rating ones back in not higher wattage ones!

Hope this helps, please click on "like" if it does.

Answered 8th Mar 2012

Electrical Safety Services

Member since 17 Oct 2011

Dear Customer,

Sorry to hear this problem with your light and your previous electrician.

The problem with your light could be malfunctioning of your LV transformer for the particular light or Thermal cut out inbuilt in transformer for safety operation if the transformer and light source are too close in your ceiling.

Other solution: Get High Power LED warm white or cool white GU10 and remove your problem forever (35000 hours ...Life) this data is from average available product from the current market.

I advise you if you can wait for few weeks than write or try to call that electrician and if you can't trust or have no time to mess around than log your small job on this web site and get different quote and help.

You have right to call electrician back within reasonable time for free check up of their work if they provided you transformer (material) as per goods and service act 1989 (please check this on Google)...

You are welcome to contact us from my builder and we are happy to help you.


I hope the above information could help you decide your next step!

All the best


Answered 7th Mar 2012


Member since 27 Sep 2011

I think the problem is with the transformer. Its either faulty or too many lights have been fitted to one transformer. The transformer has a safety cutout which turns off when over heating then comes back on when cooled down.

Answered 8th Mar 2012


Member since 30 Jan 2012

Sounds to me like the bulbs are getting hot. I would have a look in the loft and remove any insulation etc from around each fitting to ensure there is not problem there.

After that another option 'may' be a loose connection on a fitting or worse, water vapour may be getting in the fitting (I make the assumption your in the shower / bath as the lights are on a long time). Try opening a window or putting an extractor fan on when your in there

If neither he above helps it might be time to bite the bullet and get another spark to take a look.

Most tradesmen will offer to look for free anyway and only charge when they fix the problem. I would stress that if the other spark merely changed the bulbs, then any fault won't be down to him I'm afraid

Answered 8th Mar 2012

Aquarius Home Improvements LTD

Member since 9 Apr 2011

Need help with your project?

We have tradesmen ready to help you. Post a job, read reviews and hire today.

Post a job

Need some help?

Post a job on MyBuilder to find quality, local Electricians who can help you with your project.

Search all questions