i am trying to find out where the sensor is to say weather the door is open or not on a 51plate octavia.sensor will register when door is on first latch but soon as fully open sensor does not register can anybody help?

It's a very common problem buddy, mine went the same a few weeks ago, you will need to do 1 of 2 things to fix it. 1 which was the option I went for due to having no time to repair, is to replace the door lock. £167 all in and fitted.

Option number 2 is to remove the door lock and strip it down and replace the micro switch possible costing around £5

i have replaced the door lock and still have the same fault so what would be the chances of getting another lock with the same fault? so the door sensor switch is definately in the door lock?

yes it's defiantly in the locking mechanism. Like i said I had the exact same fault, had new lock fitted by central VW and all is good now. Price 1 up from Tps and it less than £99 new

Sure it's not Water ingress into the connector block on the drivers door ?

2 locks showing the same problem (normally brought on by age/use), I would go with water ingress as my first port of call. Free to check.

Think it can degrade the metal pins resulting either that it needs cleaning or the pins fall out and you need a new connector

the fault was there when i bought the car, sourced second hand door lock and still the same fault.have been into door loom as i had a fault with electric window and there was no water in there then. still have original lock so might strip that down see if i can find this stupid switch. just seems strange how it will work on 1st click of door been open but not when fully open