MK3 self opening boot & mystery items

[Schmill]

Hi all.

I have a 2012 Focus MK3 with keyless entry. Since the cold spell we had recently my boot seems to want to open itself. I think  it might be related to the numberplate light, which might make sense since it's possible it's in the same housing as the boot release touchpad... ?

Has anyone else had anything like this? It's maddening - lights on/off, the boot opens; lock the car the boot opens; close the boot, it re-releases itself 🤨 

In addition when looking under the rear of the car (trying to find the keyless entry sensor) I found these two parts - any clues on what they are?

Red tag in the writing loom behind the rear right wheelarch - my best guess was some kind of cutoff for the fuel pump?

And then this, between the rear bumper and the car body, centrally located:

I'm aiming neither is the boot keyless entry, since I unplugged the second one and the boot still unlocked!

Many thanks!

[Schmill]

Another couple of connectors, this time inside the boot, right-hand side behind the trim; grey one & white one together, and then the red one that's tapped back on itself...

Any ideas?

I've stripped the boot today, sound insulation on both sides was soaked at the bottom, now to find where the water is coming from, and whether it's that causing the problem.

I've had the boot trim all off, disconnected the numberplate light / touch-switch combo and... still playing up 😔

🤔

 

[pcaouolte]

The self opening boot is often caused by a faulty switch, the one that you would press to open the boot manually.

The water in the bottom of the boot sometimes comes from the back lights, there is a foam seal around the holes where the bolts hold the light on, fill that up with grease. More often the water is coming in around the vents behind the bumper, there is a sticky thread showing how to remove the bumper and re seal the vents after drying out the water that fills the cavities in the two back corner of the car.

[Schmill]

Cheers, I've removed the switch entirely for now to see if the problem goes away.

I think there must be a problem with it since I've noticed that when it SHOULD be off the led number plate light is still following partly:

As for the wet via the vents, I've removed the bungs and loads of water poured out, so that's a job to do at some point soon.

However I don't currently see how the water there would actually make it's way into the boot-proper?

You can see all the insulation wet here:

[Alex.S]

I’d a Fiat Uno in the 80s , when I put the hazard lights on the headlights flashed!

Back to OP , there’s threads on here re the mk3 boot leak . 

[TomsFocus]

Just FYI, the keyless antenna is that long thin black box on the boot floor, you can just see it between the two sound deadening pieces in your picture.

As for the water, it's the typical MK3 bumper vent leak!

[Schmill]

4 hours ago, TomsFocus said:

Just FYI, the keyless antenna is that long thin black box on the boot floor, you can just see it between the two sound deadening pieces in your picture.

As for the water, it's the typical MK3 bumper vent leak!

Thanks, I thought I'd read somewhere that the antenna was in the bumper somewhere, bit maybe that was a different mk. Thanks for clarifying that that is the actual antenna!

Yeah, I figured it was the standard boot leak, but I hadn't realised that it actually came into the actual boot, I thought it was in the bodywork only.

As for the numberplate light / boot switch, I've split it apart tonight, but it doesn't look like water got into it at all; PCB & everything looks fine 🤔 Bit of a mystery as to the strange behaviour, unless it was just coincidence that the switch has gone faulty at the same time as I've noticed the water...

Any clues on what they various other connecters in this thread are?

 

[TomsFocus]

11 hours ago, Schmill said:

Thanks, I thought I'd read somewhere that the antenna was in the bumper somewhere, bit maybe that was a different mk. Thanks for clarifying that that is the actual antenna!

Yeah, I figured it was the standard boot leak, but I hadn't realised that it actually came into the actual boot, I thought it was in the bodywork only.

As for the numberplate light / boot switch, I've split it apart tonight, but it doesn't look like water got into it at all; PCB & everything looks fine 🤔 Bit of a mystery as to the strange behaviour, unless it was just coincidence that the switch has gone faulty at the same time as I've noticed the water...

Any clues on what they various other connecters in this thread are?

 

Ah, there's more than one antenna!  The one on the boot floor is to detect the key inside the car - it unlocks if you leave the key fob in the boot by accident and then try to lock it.  That sounded like your issue when I skimmed the thread yesterday.  I'm not sure where the external sensor is, though the one by the bumper looks like a good culprit.  If you can get a part number or anything from it that should help determine.  

Not sure what the red tag is - but there's no tank fuel pump on these so it's not a cut-off.

Grey and white plugs look like potential towbar wiring to me.  Red looks like it's for the wheel mounted sub system. 

[Schmill]

Thanks for the ID on the connectors.

I can confirm that the one behind the bumper is / was the rear sensor:

 

There's no denying I have the "MK3 boot leak" problem, I've been addressing that:

However there's certainly something else electrical going on.

My boot release "touchpad" (with numberplate light) is disconnected (in the house!), and the rear keyless sensor is also disconnected.

Yet with ignition on, when I turn the lights on or off the boot latch is repeatedly operating. I'm presuming that as the switch isn't connected it can't be that, so then I'm left with what - the loom?

Is there somewhere I can get the electrical wiring info? There's 3 wires to the button / numberplate light, I'm assuming one is a common "something" and the other two are for the light & button, but no idea which is which.

Also does anyone know if the numberplate light comes on dimmer with sidelights that with normal lights?

 

 

[Jon RB]

Just started having this same issue myself with my 15 plate mk3, key fob for all doors doesn't seem to open the boot however the boot release only opens the car fine, and the boot is the same opening and trying to close or reopen while driving, ain't sure if it's just straight up wiring issue or some sort of sensor, did you guys find anything more out?

[Schmill]

3 hours ago, Jon RB said:

Just started having this same issue myself with my 15 plate mk3, key fob for all doors doesn't seem to open the boot however the boot release only opens the car fine, and the boot is the same opening and trying to close or reopen while driving, ain't sure if it's just straight up wiring issue or some sort of sensor, did you guys find anything more out?

Unfortunately (or perhaps fortunately) mine seemed to have been entirely related to the fact that a large portion of the wiring loom and connectors was soaked from the water ingress problem - thread here: 

 Have you checked for the water?

After I cleaned and dried mine I took the boot switch apart entirely (carefully) and cleaned up all the contacts internally, checked it was all working (with a test meter) and then sealed it back up with some super glue.