Disconecting a battery - how long?

[Kenny6868]

I have an issue with my headlights. Basically, selecting full beam only illuminates the dipped bulbs. So I have no full beam at all. Otherwise the lights do as expected.

I've been told that disconnecting the battery should reset the ECU and everything should go back to normal. I tried this at the weekend but it didn't make any difference. I only disconnected it for 2 or 3 minutes. I'm now thinking maybe I should have disconnected it for longer. Any ideas?

The car is a 2014 Renault Megane GT-Line

[eybic]

Something that is recommended on some cars is to apply the brakes when the battery is disconnected to discharge the electrical system.