Anyone any idea where the convenience unit on a 1999 1.9 Octavia sdi hatch is located. Ive had the drivers door card off but nothing obvious there. The locks are key operated and no electric windows. The locking bolts are shooting up and down whilst I'm driving along albeit I can stop this by pressing the passenger side lock bolt down. Water has obviously got into the unit wherever it is located. Ive searched other threads and mention is made of it perhaps being behind the dash, if so where abouts behind the dash and how do I get at it.

It is on sitting on a bracket behind the dash panel that has the headlight switch on it. I doubt that water has got into the convenience unit.

What it is the problem?

The problem is the door bolts bolts shooting up and down,as mentioned it does this whilst I'm driving along but I can stop it if I press the drivers side bolt down. It also does it with the engine off if the car is left unlocked, the doors will just continually lock and unlock themselves until I lock them with the key. I can hear a clicking noise behind the dash when the doors lock themselves which presumably is a relay.

The reason you hear about water corroding the convenience unit contacts, is that it is located in the drivers door on other models. This does mean it cannot go wrong for other reasons.

More likely causes are:

1. The controller for the driver's side door (windows, mirror, door lock, etc) goes wrong. This is part of the the window motor.

2. There is a fault on the door wiring loom where it passes from the door through the 'A' pillar.

3. There are microswitches in the door lock mechanism. There can wear away and also can suffer from dry joints.

Manhandle the wiring loom as it passes from the door through the 'A' pillar. If this has no effect then you can eliminate the driver's door electrics by removing the plug from the driver's door window motor. If all the other doors still lock/unlock on their own then it is probably the convenience unit.

Look at http://briskoda.net/octavia-i/door-lock-malfuntion-maybe-cure-your-problemo/63827/ for info on the microswitch problem