Technical Doors lock/unlock on their own

[sludgeguts]

Even whilst driving along. As long as the fob is within range!
I noticed the led on the fob was flashing so figured a new battery was needed (original from 2010). But the central locking still activates at random.
Any ideas?

 

[the green vanper]

Usually the central locking is controlled by the BCM. I'd check contacts (especially around the BCM), earths (especially the strap earth body to engine / gearbox and replace it).

Is the PCB in the fob clean? No oxidation visible?

 

[ZaphodB]

TACT switches of all shapes and sizes (like within your fob) are well known to develop a partial resistance (instead of being completely open circuit when not depressed)
This resistance can trick the processor on an internittent basis that you're pressing the button when you're actually not (a ghost press)

They are also known to get virtually destroyed in remote fobs by excessive pressure when operating them... as the contacts tarnish and get worse users often press them harder and harder exacerbating the problem. ... (and they also can come loose off the pcb with lead free soldering)

Hard to do when driving , but see if you can see the LED flashing when it attempts an unlock

 

[The Panda Nut]

Have you tried driving the car with the standard non remote key. This will narrow it down to remote fob or car.

Start simple if it seems to be the car and clean the fob. A can of electrical cleaner can be used liberally.
My next suspect would be sticking booy latch. The pivots carry road dust and get tacky. Brake cleaner was my referred thing, but you may have to remove the lock so you can really get at this. The I agree with The Green Vampers suggestions. Anything else is more involved. If you try these first and see what happens hopefully It will resolve.

 

[koalar]

Thake the battery out of the key and us it as a manual key

If it stops the key is the problem

Most likely the buttons switches

 

[ZaphodB]

Have you tried driving the car with the standard non remote key. This will narrow it down to remote fob or car.

He's already kind proved 100% it's the fob with it doing it only when the fob is in range of the vehicle.

clean the fob. A can of electrical cleaner can be used liberally.

I wouldn't spray any form of cleaner on it apart from iso-alcohol , this will completely evaporate.

I think it's a dodgy tact switch personally (electronics is my day job ) and cleaner won't sort that

 

[The Panda Nut]

Useful to know. One of ours is playing up. I changed the battery but not much difference I suspect the buttons need cleaning. These batteries are often no good when you buy them so another new one first. Out Tv remote used to need pulling apart and cleaning rather to often may be tge same sort of thing. Clean kitchen towel worked on that. Im out of electrical contact cleaner so more spending needed.

 

[ZaphodB]

Remote controls generally use rubber membrane (carbon doped) keypads , which push directly on a gold plated contact pad (the carbon dope button shorts the contact pad.. the rubber contact pad generally wears out becoming non-conductive, so a different end result, they just end not working.
You can get conductive (silver doped) paint, but the repair is short-lived, and cleaning then generally removes more of the carbon, making it even worse.

The tact switches used in fobs and lots of control keyboards on all sorts of products, on the other hand, are sometimes well known to develop "a resistance" where they should be completely open circuit when not pressed. This really confuses some microcontrollers/microprocessors and they end up intermittently thinking you're pressing a button.

 

[Mike1alike]

Had the exact same problem on my Punto. Fixed it by cleaning the contacts on the cables and alarm control unit. The remote key locker communicates with alarm unit on mine, it's a separate little remote, not integrated in the ignition key.
Cleaning those contacts fixed it but also in short time after, I discovered I had bad earth cable, fixed that too and also discharged battery. I did think at the time and also now that faulty earth and discharged battery might have had something to do with that problem. The fault never came back and it was really freakish first time it happened, doors unlocking and locking repeatedly while driving.

 

[koalar]

It's not rocket science

You don't have to take wild guesses

First establish it the remote

Take the batteries out, the fact it's flashing while driving (sending), probably means you can skip this step, I wouldn't, for the sake of 10 seconds and a test drive, I have seen weird unexpected results when double checking things and end up going down a different path

Then establish if it's a problem with the buttons in the shell or on the PCB

Try PCB without the outer shell

It's 50/50 whether it's a button pushed in too far on the shell or a faulty button on the PCB

Either reshell or change the button

Just for clarity

We are talking about one of these

Physical button not membranes

It's not the ECU or body computer or anything in the car in my opinion

The button are replaceable

They are surface mount, but they aren't that difficult to change with the correct equipment and skill, they are quite big pads by mobile phone standards

If you are near me (Crewe) and If needed, if you supply the buttons around a fiver for three, I will change them free of charge


It's quite easy to change the shell, just make sure you order the correct one

The inside from one type will not fit the other

Odds are it's the second

Be careful taking the PCB out, it's easy to damage the component on the thin strip, top right on the picture of the PCB

 

[sludgeguts]

Thanks everyone. not too great at the moment so will give the suggestions a try as soon as i can