'05 Focus Tailgate/boot Problem

[Dave67]

Have a mk2 focus boot unlocks when you brake. Taken rear brake lights out disconnected them and it stops doing it when brake pedal is pressed but as soon as you plug any brake light back in it triggers the lock. Changed switch and lock still the same. Put the old parts in another focus and they work fine. Still investigating problem. By the way lock works as it should with all brake lights disconnected will post solutions if I can find one.

[Tdci-Peter]

34 minutes ago, Dave67 said:

Have a mk2 focus boot unlocks when you brake. Taken rear brake lights out disconnected them and it stops doing it when brake pedal is pressed but as soon as you plug any brake light back in it triggers the lock.

The tailgate latch earth wire is common with the earth wire from the high level stop lamp. An open circuit here could mean the tailgate latch gets energised when the brake lights go on. Also the latch, high stop lamp and left main stop lamp all have a common earth point on the left wheelarch. The other likely fail area is the rubber flexi-cable between the body and the tailgate. Wires have been know to go open circuit in here.

I can not work out a single simple fault that creates your exact symptoms, but these are the wiring areas I would investigate first.

[Dave67]

Thank you checked all the areas you have said but still have same fault. Cleaned earths strip every think to expose wiring loom no shorts rubbed wires replaced lock and switch. All bulb holders and high level light still no joy. Will have another look sometime. In the meantime will just lick the doors while driving. Once again thanks

[Tdci-Peter]

2 hours ago, Dave67 said:

Cleaned earths strip every think to expose wiring loom no shorts rubbed wires replaced lock and switch. All bulb holders and high level light still no joy

Sounds like you have investigated the rear end quite well. There is another possibility. I could not see a simple electrical fault at the rear that would give your symptoms, but the PJB/BCM/GEM/Passenger Fuse box (call it what you like!) could do exactly that.

And it is prone to suffering from corrosion due to water.

The circuit from the brake switch goes direct to the brake bulbs, delivering 12v at quite high current. Cold filaments take a big inrush. But it also goes into the PJB. Corrosion causing tracking between pcb traces could couple the brake signal into the tailgate latch circuits, most likely into the switch circuit. Any sparking at the worn contacts of the brake light switch would make this more likely. It might be worth stripping the PJB down to have a good look at the pcb tracking. Sometimes they can be cleaned up ok.

[Snoop13]

BOOT LID OPENING WHEN BRAKE PEDAL PRESSED/RELEASED FIXED.

If your having this problem with a mk2 focus then check the rear lamp plug sockets on both lamps for corrosion (not the bulb holders but multi pin pugs inside the car), this one had severely corroded on the near side lamp now its been cleared and greased the boot lid is now operating correctly 

GOOD LUCK WITH YOURS!!!

[Snoop13]

BOOT LID OPENING WHEN BRAKE PEDAL IS PRESSED/RELEASED FIXED

 

Severely corroded terminals in rear lights multi pin plugs inside car(not bulb holders)cleaned and greased now operating correctly. 

GOOD LUCK WITH YOURS 

[SueMax]

My 07 Focus hatch Zetec has just developed this problem.  I can hear "random" operation of the rear hatch lock (am using car like a van so there is an open space, seats folded down).

The tailgate won't open on the rubber-covered "grab catch" but the tailgate is "on the catch" and rattles.  The red light is flickering then on all the time.  The use of the brake pedal seems to affect things too.

It SEEMED to me that movement (speed humps, movement of the items near the tailgate on tight bend, etc) affected things too, so I suspect mine is broken wiring related or earth lead not "water in the switch".  I will investigate the large black connector and the individual connectors.  Condensation may be an issue (car is one space and of course we have had tons of rain).

Not tried the key fob but hopefully it will work!  Until reading this I hadn't thought it was anything barring a faulty switch.  Never used the fob for the tailgate so didn't think to try it - I thought I had a physical problem, especially since the tailgate is not completely closed.

[Alan Taylor]

Just had this problem with my focus every time i release the break pedal the boot clicks and opens. I replaced the micro switch in the handle but that didn't work. Read a post eventually about pulling the carpet down on the passenger side in the boot to get to the large connector, the one with the wires from the 3rd brake light, i unplugged this and sprayed with WD40 then clicked it back together, also sprayed the lock mechanism and hey presto it works!!

[The tyre man]

If no one has solved this I may just have the thing my partners focus 2005 boot was opening it’s self I tried everything then I thought I’d dig further pulled all the panels off in the boot and removed carpet over passenger side rear arch there is a big block plug disconnect it and clean it mine was full of water once cleaned and dried the boot lock worked boot stopped popping open and has still to let me down so before spending give this a try 

[Vicki2021]

Hi I have had a boot problem for 18 months On my 2005 focus I changed the switch and boot lock was ok for 2 weeks Then prob was back so I took to ford who done the same and charged me £200 it was ok for 2 weeks again Finally I’ve managed to find problem I hope this helps someone inside the boot on left hand side behind carpet is a large electrical plug which I think is all mains electric for all rear electrics when it rained this plug was getting wet and causing several electrical problems I’ve now placed in a dry spot no more problems 

[StephenFord]

On 7/7/2021 at 4:44 PM, Vicki2021 said:

Hi I have had a boot problem for 18 months On my 2005 focus I changed the switch and boot lock was ok for 2 weeks Then prob was back so I took to ford who done the same and charged me £200 it was ok for 2 weeks again Finally I’ve managed to find problem I hope this helps someone inside the boot on left hand side behind carpet is a large electrical plug which I think is all mains electric for all rear electrics when it rained this plug was getting wet and causing several electrical problems I’ve now placed in a dry spot no more problems 

mmm... just like the very post before you LOL 🤣

[troy45]

While cleaning and drying the connector seems to sort the issue for people I don’t think that’s classed as a wet area of the car so would help to find the source of the water leak. Guess there’s lots of posts covering that on here for the mk2 & mk2.5. My own experience being water leaking through the locut inserts for the rear light fixing screws.