Flickering head/tail lights EK civic

Hey guys, so both head and tail lights are flickering in my EK Civic and I haven't been able to figure out why.

What I've done so far is inspect fuses underneath steering column and under the hood. I've swapped the battery with a known working battery from another car but it still happens. This issue occurs even with the engine off so is it safe to assume that this is not an alternator issue?

I'll try cleaning the battery terminals and sanding the area where the grounds are connected to the chassis tomorrow during the day however on my brief inspection so far, all appears good.

Is there anything else I should look for that I have missed?

Thanks.

Light switch and associated wiring / connectors

could be a loose wire somewhere

Doubtful it has anything to do with the grounds, as headlights and tail lights have their own local earth points. The common part of the circuit starts at the battery, through the under bonnet fuse box which feeds the light / indicator switch. The circuit splits at the light switch (separate terminals to the tail lights and head lights) so I think your problem lies between the battery and the switch (most likely the under bonnet fuse box, or a connector between there and the light switch). It isn't necessarily the fuse - it could be a loose connection in the fuse box itself, or poor contact between the fuse and holder (corrosion on the terminal). This is not uncommon.

By the time the circuits reach the under dash fuse box, they have split, so this won't be the issue.

Thanks for the help mate. I've been so busy lately I haven't had a chance to properly check everything out. I'll post back here if I fund anything around the fusebox. Also if it helps barrow things down, the flickering happens to the dash and radio too

If everything is flickering then you need to back trace it to the most common power source. You don't have a high power car audio set up do you?

Nope, the car is completely stock. I'm struggling to find anything, mainly because I don't even know what I'm looking for. Was hoping there would be something obvious. Think I'll just take it to an autoelectrician to fix. Thanks for the help anyways guys, much appreciated.