Interior Light - Not triggering

[SamCappo]

Helllloooo there 

Just picked up a MK3 zetec s, really lovely car. 12k miles on the clock and 1 very careful previous owner. It's 5 years old and only done 12k, unbelievable. Anyway......

Everything works as you would expect on a 12k miles car, except the interior light, it works manually when pressed just doesn't when I unlock my car, open my door or turn off the ignition.

The interior light "off" button has definitely not been pressed. Any ideas? Could I have a potential voltage problem because car hasn't done any miles? But I've kinda ruled this out because stop start works fine!

Any help greatly appreciated! Many thanks 

[E TEA 66]

I take it you've tried the other doors then although I know that sounds obvious but sometimes it's easily overlooked if it's just yourself using the car and could well be just a broken connection in the switch on the B pillar or the switch could be stuck for that matter as I once had slight  water ingress witch very slowly rusted the switch connectors until it finally stuck in the off position so a proper check would be worth while .

[SamCappo]

8 hours ago, E TEA 66 said:

I take it you've tried the other doors then although I know that sounds obvious but sometimes it's easily overlooked if it's just yourself using the car and could well be just a broken connection in the switch on the B pillar or the switch could be stuck for that matter as I once had slight  water ingress witch very slowly rusted the switch connectors until it finally stuck in the off position so a proper check would be worth while .

Hey mate.

I have tried every door yes. Boot light and glove box light are both working fine. I've got a tiny tiny bit of wet boot lining down the left hand side so water ingress is likely. I'll check the rear quarter cavities behind the air vents because I've been informed these need sealing.

Let's just say the switches are working correctly, unless they've gone in every door lol. Is there anything else it could be? 

Appreciate your advice :-)

[JW1982]

On the Focus MK3/MK3.5 the microswitches are fully integrated into the door locks. the switches inside each lock are connected directly to the BCM (Body Control Module). The interior lights are digitally controlled by the BCM through a LINbus network. The front interior light passes the signal through to the rear interior light.

The switches in each lock can easily be checked. If one of the switches is stuck or broken the vehicle can not be locked or the "Door Open" message will not be functional for one or more doors. If this all works correctly the locks will be fine. 

 

I expect the problem to be caused by a communication problem. This can be caused by either the BCM, the (front) interior light or the wiring.  

[SamCappo]

1 hour ago, JW1982 said:

On the Focus MK3/MK3.5 the microswitches are fully integrated into the door locks. the switches inside each lock are connected directly to the BCM (Body Control Module). The interior lights are digitally controlled by the BCM through a LINbus network. The front interior light passes the signal through to the rear interior light.

The switches in each lock can easily be checked. If one of the switches is stuck or broken the vehicle can not be locked or the "Door Open" message will not be functional for one or more doors. If this all works correctly the locks will be fine. 

 

I expect the problem to be caused by a communication problem. This can be caused by either the BCM, the (front) interior light or the wiring.  

Hi Wilco,

This is a really eloquent explanation of the lock switches, my doors definitely lock so I'm pleased to know the switches are still operational.

Where is the BCM located, towards the rear? Could it be affected by my leaky boot vents?

Unless it's just in hibernation as it's not been driven enough recently? The previous owner only did 40 miles a week lol.

Car electrics are a nightmare aren't they?! I'm glad you know what you're talking about because I certainly don't haha!

Thanks again!

 

[E TEA 66]

Sorry I couldn't be more helpful as it would seem the mk3 is somewhat different to the mk1 that I have going by what Wilco has said so fingers crossed it won't be too long before you find the issue although if it was my issue I would be consulting the wiring diagram in a Haynes manual in order to trace each part of the setup .

[SamCappo]

1 hour ago, E TEA 66 said:

Sorry I couldn't be more helpful as it would seem the mk3 is somewhat different to the mk1 that I have going by what Wilco has said so fingers crossed it won't be too long before you find the issue although if it was my issue I would be consulting the wiring diagram in a Haynes manual in order to trace each part of the setup .

You've been very helpful It's all new to me this stuff.

Thank you!

[gillyallan]

Could be the switch that disables the light that is broke in the off position

[E TEA 66]

1 minute ago, gillyallan said:

Could be the switch that disables the light that is broke in the off position

It could be so it's worth checking it out even if it isn't the issue at least it rules it out although it would make for an easier fix if it is so fingers crossed for you 😉  .

[Phil21185]

Hang on, this isnt an option via the IC is it?  Or am I thinking of the ambients?

[SamCappo]

The switch to disable the interior light does illuminate when pressed. I don't know if that indicates the switch is still operational. What's an IC please? Lol!

 

[SamCappo]

20 hours ago, gillyallan said:

Could be the switch that disables the light that is broke in the off position

Could I check this quite easily?

[TomsFocus]

Are you trying just the front interior light or the other one as well?  I think the other light affects both, so if the door open switch is 'off' on that one then neither will work.

IC is instrument cluster - aka dash clocks where the speedo etc is.  

[SamCappo]

1 hour ago, TomsFocus said:

Are you trying just the front interior light or the other one as well?  I think the other light affects both, so if the door open switch is 'off' on that one then neither will work.

IC is instrument cluster - aka dash clocks where the speedo etc is.  

Hi Tom,

There are no buttons on the rear interior light. Just a dome - I've got a zetec s, not a flashy titanium  i've obviously got the very bare bones haha! I'll have a look on the IC to see if there is a setting...

I've booked it into main dealer on Monday to sort out the water ingress in boot (rear vents) after your recommendation in the other thread, so they're going to take a look at the interior light as well :-) - not confident they will sort out either of them mind abut their service has been phenomenal so far

EDIT: Just been out and checked the IC screen settings menu, can't do anything here except change the dimming to manual/auto. 

[TomsFocus]

Hmm...maybe I'm thinking of a different car!   You won't have ambient lights on a ZS but I doubt they'd remove an interior light, I'll have to check mine next time I go out.

[gillyallan]

Is the 3 the same as the 3.5 (mine} where it has a button on roof that disables the door activating it?
It's definitely not that? Or that that's faulty?

Or if it has it, something like valet mode.

[SamCappo]

44 minutes ago, gillyallan said:

Is the 3 the same as the 3.5 (mine} where it has a button on roof that disables the door activating it?
It's definitely not that? Or that that's faulty?

Or if it has it, something like valet mode.

Yes it has the button on the roof that disables the interior light when the doors are open and I have definitely not activated it. I've recently popped the housing off and unplugged, checked the connector etc and all seems fine. It's so weird!

All my sidelights come on when I open the door and the registration plate light, I assume this is supposed to happen? 

[gillyallan]

Yeah that happens.

 

Does the disable button change colour when you've disabled it? I'm sure mine goes orange.

 

 

[SamCappo]

6 hours ago, gillyallan said:

Yeah that happens.

 

Does the disable button change colour when you've disabled it? I'm sure mine goes orange.

 

 

Thats good to know.

Yes it goes orange still. Switch appears to be working fine. It can't be down to my key programming either.

I wonder if it's anything to do with my key programming? I'll try and manually unlock and open the door to see if that makes a difference.