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Full Version: Fix Boot Lid Lock Random Opening Problem
Ford Owners Club - Ford Forums > Ford Models > Ford C-Max Club

The wife's CMax started playing up the other day. I knew for a while that she couldn't open the boot using the switch, only the remote button could unlock the boot. No big deal, so we left it.

However, a couple of days ago, the boot started opening at random times, mainly when the car was started. It quickly progressed to opening whilst driving or sticking it into reverse.

I had a look on here and the internet. It looked like I might have to shell out a few quid for a new switch. I read that recently someone had used a small button switch from a mouse, so I thought I'd have a go at that before giving my hard earned cash to the people who designed the car badly in the first place!!

Tools required....

Hex bit for screws in grab handles
10mm spanner (ratchet spanner preferred)
Soldering iron and solder
An old computer mouse
Silicon sealant.

This is what I did;

I removed the 2 screws in the grab handles at the bottom of the bootlid cowl. Then I gently prised the cowl off the bootlid. This was surprisingly easy to do and none of the clips or plastic broke.

I then loosened the 4 nuts that hold the outer plastic trim using the 10mm spanner (where the boot switch is located) onto the boot. I prised this away from the bootlid and pushed in the grey plastic clips on the side of the switch mechanism which released it. I then unplugged the switch from the loom and removed it from the car (along with the grommet). (You can see I had 3 switches lined up to see which fitted best, 2 were from the mouse and one was from an old led bike light)


I peeled back the rubber 'gaitor' from the switch and found the same white powdery stuff that others have found, which meant that water ingress was probably to blame. I gave this a good clean and had a play with the switch to see if it still worked. The multimeter told me it was intermittently faulty.

I removed the original seal where the wires join the switch and pushed the switch out from the bottom of the plastic trim.


I found an old mouse and butchered it. I got out my old soldering iron and removed a couple of hopeful switches, stabbing myself in the palm in the process. I am a rubbish solderer, so if I can manage it, everybody else can!!


I cleaned up the plastic trim and dried it thoroughly.


I then de-soldered the original switch. I fed the wires back through the little gap and soldered the new switch on. Took me half an hour because I'm terrible at it. A couple of burns later and it was done.


I had some strong superglue lying round, so I used that to fix the new switch in place, making sure it lined up with the button in the trim.


I didn't have any clear silicon sealant so some white anti-mould shower sealant had to do the job. I plugged up the hole by the wires thoroughly with the sealant and made sure it was neat inside the trim.



Next up was putting the rubber trim back in place. Some careful application of the sealant later, and the whole switch was watertight (hopefully).



I put it all back together and for the first time in a couple of years the boot opens using the switch. The random problem of it opening seems to have stopped as well.

It's early days but looks promising. Only took an hour or so and didn't cost me a penny either!!

This seems to be a common problem with CMAX's and Focus' between 04 and 07. I've put this in a couple of places as well to help as many people with this problem as possible.
Hi Lippo
Thanks very much for this, i have problems with mine intermittantly not working (it doesn't open itself but sometimes doesn't open at all - the number of times i've emptied the boot by folding the rear seats down!!!).
I'm going to strip mine down now i know its so easy, thanks again for the well illustrated info.
Hi Dickster,

If you haven't got a mouse to dissect, I had a quick look on Maplin and found the following which seems similar to my switch;

These seem to be around the right size; SWT105 4.3mm Black or SWT105A 5.0mm Black.

Or these;

I haven't seen physically seen these but the type/size seem about right. Good luck!

Thanks for that, i'll let you know how i get on in the next couple of weeks
I must say a big thanks to Lippo, i have a 54 c max and the other day my boot would not open,i had a old dvd player which didnt work and got 5 little black micro switches out of it,followed Lippos instructions and 10 mins later my boot works again.the photos were a big help. Andwill have saved me a few pounds.many thanks again Lippo
I just did this for my wife's Mk2 Focus and the boot switch now works perfectly. Thanks so much Lippo!
thanks lippo :D
Thanks for this thread - I've just done the repair to my bootlid catch with a micro-switch from an old computer mouse. It works!
My boot latch had been annoyingly popping open every few weeks for about a year; then a few weeks ago the frequency suddenly increased so that it seemed to pop every time I got back in the driver's seat after slamming the boot closed!

I found this great thread from a Google search and I followed Lippo's instructions. It all worked perfectly (apart from a few burns from inexperienced soldering) and a great feeling of self satisfaction has set in. It takes me back to the old days when you could really do DIY stuff on your car.

So thanks Lippo, for saving my sanity; I couldn't have taken the aggro for much longer ;-)
I'm really glad that people found this useful. Mine is still working perfectly, even in the freezing weather.
I know this is an old thread but i stumbled across it a couple of days ago whilst trying to find an answer.
My Focus (MK2) boot handle was not working since i bought the car whitch i didn't really mind as i just used the key. But it started unlocking on its own unless the car was locked. This got really annoying really quick.
Iv searched around any there docent seem to be a definitive answer. Mainly just people saying that it was down to water ingress.
so i thought id have a little mess with it and see what i could do.

I peeled back the rubber of the boot handle to find i full to the brim with water and a white power/residue

After i seen how bad it was i took it apart from the inside and gave it a good clean. Wiped everything and gave anything Easily detachable a good soak in the sink.
It was a hot day so i drove around without the Rubber on the handle to air it out.
And then Blasted the handle and cover in WD40 (to evaporate any left vapour).

Since putting it back together its been fine. The boot handle still does not work (in need of a new switch). But it sees to have fixed the unlocking problem.

Hope this helps.
Having read this thread I decided to try and change my own switch.
Not wanting to attempt repairing or soldering I took the decision to buy a new one.
I bought a genuine Ford part from a main dealer for £12, much less than I had been led to believe on here.
In fact I looked on ebay first and they all wanted £30+

Changed the switch in less that 30 mins
Big thanks to Lippo for an easy to follow guide that took no time at all to fix my annoying self opening boot well chuffed an im not bothered if i have to do it again in six months because of how quick and easy it is to fix .......great post tnx.
An excellent guide, I will pin this appropriately. I will have a word with the other mod's and see if we should have a CMAX "Guides" section, or wether we shall move it to the general "guides" section...

 Many thanks for all the kind posts.


 Quick update; after working seamlessly for over 2 1/2 years, the switch has stopped working again. No random opening this time, but I'm still assuming it's the switch. I'll have a go at it in the next few weeks.



Peter N

Having just completed this repair, thanks to Lippo, I thought I should add something to the topic.

The cause of the problem appears to be,

1 The use of the switch acts like a bellows and sucks air in.

2 As the metal plate cools it allows the water in the air to condense out.

There's not a lot that can be done about 1 but you could replace the metal flap with a plastic one (as I have done). I will check in a few months to see if there is any water there and report back.




did you get this repaired again Lippo?


I am due to do mine soon, got to buy the bits for it and need to find a victim mouse! did you have to desolder, or could you get away with cutting the end off and solder a new end to the new switch?


glad i found this as my boot lock is playing up,


can someone please update the maplin links on page one as not working.





I bought



cant recall which I used though it was a while ago.


I bought



cant recall which I used though it was a while ago.




which of the 4 connection points do i solder to?





If you look at the bottom of the switch you will see them.


It will show a line going from one pin to another, I cant recall if its next to each other or opposite, but it will be like this:




*    *




*   *

 |   |

*   *


each * is the leg, so you just follow it, the switch connects each of the connected stars.


hi there folks been having some issues myself an thought id see if you guys have any thoughts.


so the switch stopped working, I was doing some work on the rear tail lights at the time so there is a possibility something may have gone a bit wrong but as far as I can tell everything was isolated.


anyhow, the remote unlocks the tail gate work but the switch doesn't.  there are two feeds going in to the switch, a neutral and a 12v live (white).  the switch is off by default and when pushed in creates continuity so as far as I can tell that switch should be working.


tracing the 12v live (white) back in to the boot it runs off towards the front of the car,

the neutral follows the same path and joins up with a netural from the reg plate lights and tail gate lock, and wiper motor all maintain continuity.


my guess is that white from the switch runs off to some sort of control but at this point im stuck, I cant see any mention of a fuse or a relay in Haynes but with power going to it im a little stumped. 


soo does anyone have any ideas?



edit, bugger, just realised im not on the focus sub forum! oops! ah well it should be much the same setup...


Hi Mate,


They are pretty much the same setup any Ford these days.


It sounds like your switch has probably given up the ghost. I think the white line goes off to the gem and powers the boot switch, but its a small enough current that whatever you did probably was not to blame.


I would say pop the plastics off the car, and remove the switch, short these two wires out and the catch will probably click as you expect it to, then you can just fix it from there :)

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