Rear passenger door lock has a mind of its own

Hi guys

I’ve got a strange problem with my rear passenger door

When using the key fob all the doors open about 90% of the time. The other 10% the rear passenger door lock has a mind of its own and stays shut.

I thought it might be the battery and swapped it and it started to work fine.

Then after a few month my wife opened the car using the key (Not the remote)
I took the key to work and our spare key had no battery so she went old school and used the key ……. It only opened the three doors but not the rear passenger door.

When I got home I used the key fob and again it started to work fine.

Until last week it started to play up again

After doing a bit of research I thought it was a faulty door lock.

So I ordered a used on from ebay and fitted it this weekend ……. Works perfect for 2 day as an then …….. its not working again.

Strangely, if I give the key fob a double unlock click it will open the rear door …… but this not all the time maybe 50/50

Its annoying me and also dangerous as that door is used for my 2 month old daughter .

Any advice or help would be appreciated !!!

Thank you for the reply !

Where about's should I check ?

Within the door or the rubber bit in-between the door and the body ??

Sorry,

Just thought the door might have many rubbers inside it

I'll check, thanks !

Well, I've checked the rubbers and they are perfect

Any other ideas ????

I've replace the lock and it that has not worked.

So I'll get it into the garage and do some diagnostic tests with the measuring blocks

Thank you