Hello all. I have a problem about the interior/dome/map light. 

The light is controlled by a press-type switch button.  The light can be switched on/off manually but it remains off when door opens.  The other interior lights in glove box & boot are functioning normally.  I guess the door sensor is working fine as warning would be shown on dash.  The fuse is checked and is intact.  Battery voltage is >12V.  Does anyone have any idea of what's going wrong? TIA.

Hi Simon, welcome.

Firstly, it would help if you could include full car details in your profile. 2018 was a changeover year for the Focus so we don't know if you have a very late Mk 3 or an early Mk 4 (the current shape).

I often find my interior lights don't come on automatically, even when the boot light does. Problem is invariably low battery voltage - it needs at least 12.4v for everything to work (see below).

You don't mention how long you have had the car or if this is a new issue but most of us with recent Fords, especially those with fairly low/irregular usage, have found a full cycle on a smart charger every 5/6weeks does the trick. (Unless the battery needs replacing - they rarely seem to get beyond 4 years these days.)

 

 

 

On 1/19/2026 at 6:05 PM, Eric Bloodaxe said:

Hi Simon, welcome.

Firstly, it would help if you could include full car details in your profile. 2018 was a changeover year for the Focus so we don't know if you have a very late Mk 3 or an early Mk 4 (the current shape).

I often find my interior lights don't come on automatically, even when the boot light does. Problem is invariably low battery voltage - it needs at least 12.4v for everything to work (see below).

You don't mention how long you have had the car or if this is a new issue but most of us with recent Fords, especially those with fairly low/irregular usage, have found a full cycle on a smart charger every 5/6weeks does the trick. (Unless the battery needs replacing - they rarely seem to get beyond 4 years these days.)

 

 

 

And we'll never know

On 1/19/2026 at 6:05 PM, Eric Bloodaxe said:

Hi Simon, welcome.

Firstly, it would help if you could include full car details in your profile. 2018 was a changeover year for the Focus so we don't know if you have a very late Mk 3 or an early Mk 4 (the current shape).

I often find my interior lights don't come on automatically, even when the boot light does. Problem is invariably low battery voltage - it needs at least 12.4v for everything to work (see below).

You don't mention how long you have had the car or if this is a new issue but most of us with recent Fords, especially those with fairly low/irregular usage, have found a full cycle on a smart charger every 5/6weeks does the trick. (Unless the battery needs replacing - they rarely seem to get beyond 4 years these days.)

 

 

 

Hi Eric. Thank you for the information.

The Focus is a late MK3 (or MK3.5? not sure), and the battery is 3 year old. I owned the car for over 4 years.

Regarding the auto-light issue, it remained faulty after a 200 mile motorway drive in last month. But only a couple of days after this post, the function suddenly revived! I didn't manage to check the voltage beforehand so the cause of the issue is still uncertain.

Thank again for your help.

46 minutes ago, Simon EC said:

But only a couple of days after this post, the function suddenly revived! I didn't manage to check the voltage beforehand so the cause of the issue is still uncertain.

That 's good! Mines not working at the mo - even the boot light! But after 8 years of this behaviour with my current and previous car, I've given up bothering much as long the darn thing starts!😀

Incidentally, the steady motorway run is of little help with charging these days - lots of varied driving with plenty of engine braking is more effective. Plus using a smart charger periodically as mentioned earlier.

50 minutes ago, Simon EC said:

The Focus is a late MK3 (or MK3.5? not sure), and the battery is 3 year old.

Yes, the later Mk 3 Focus (after the facelift for 2015 model year) is usually identified as a Mk 3.5 for ease of reference. I'd recommend you add this to your profile.