Hi all.

I hope that you technical wizards can help with this problem, the car is 2003 Octavia 1.9TDi Elegance, The problem is: remote central locking, electric windows, lights on buzzer, door open warning light,and interior light all fail together. Been to main dealers who suggest Convenience unit or possible wiring fault is to blame. Have fitted another Convenience unit from another Octavia (same spec) fault does not transfer to the Convenience unit donor car but remains on the faulty car. Local garage suggested a faulty driver's door locking mechanism, they replaced it but the fault remains. We have discovered by chance that removing fuse 14 and refitting it cures all the above faults, albeit sometimes only for a short time, sometimes for a couple of weeks. Has anybody any idea why removing/replacing the fuse would make the fault cure itself. It is baffling everyone who attempts to find a cure. When the car returned from the local garage having had the new door lock fitted everything was working OK, parked the car on the drive, locked it using the remote, come next morning and the remote would not open the car, but it opened using the key in the lock, this is the only way to open the car when the fault is present. I hope that somebody know what the problem might be as it is beginning to get me down now. Thanks in advance.

What do you mean by convenience unit (CU)?, as often here people get the CU and door control unit confused. The CU is behind the light switch, you have to remove that part of the dash to access it, the door control unit is in the door and incorporates the window motor, there is one for each door.

The door open warning light and interior light are operated from a micro switch incorporated into the door lock, the lights on buzzer will only work if the micro switch works. The replacement of this seems to rule out the micro switch. The next link in the chain is the CU as it reads the door statuses and sends signals to activate the interior lights etc.

Has your local garage checked the CU for faults and looked at the measuring blocks to see that what the CU is reporting is plausible?

Fuse 14 covers:

Interior lighting, central locking system, interior lighting

(without central locking system)

Presumably this is the power supply to the CU, so very much like restarting a computer, removing and reinstating the power to the CU will reset it.

I am of the opinion that you may be looking at multiple problems, one with the CU for the door switch problem and another for the remote locking. I suspect that the remote locking may be a broken wire in the multiplug to the drivers door control unit, the yellow/red wire that usually breaks very close to or within the plug, disturbing it during the lock change may have moved it enough to make contact for a while. This multiplug is also known for holding water and rotting the pins off the door control unit.

Even if you replaced the CU you won't know it has sorted your remote locking until you program your remote to it.

Hi fordfan

I have swapped the CU from another car into the faulty car and the fault persists, the CU from the faulty car was put into the "good" car and the remote locking worked using the remote key from the faulty car. We have remotes to both cars and the fault still stays with the faulty car. The CU is the one that is located behind the light switch.I presume that the local garage has gone through everything as they pride themselves on being able to diagnose faults pretty well, this one has them beat!! Same problem has re-occurred again tonight, replaced the fuse again and everything works, until morning?.

Thanks for replying, any other ideas very welcome.

What do you mean by convenience unit (CU)?, as often here people get the CU and door control unit confused. The CU is behind the light switch, you have to remove that part of the dash to access it, the door control unit is in the door and incorporates the window motor, there is one for each door.

The door open warning light and interior light are operated from a micro switch incorporated into the door lock, the lights on buzzer will only work if the micro switch works. The replacement of this seems to rule out the micro switch. The next link in the chain is the CU as it reads the door statuses and sends signals to activate the interior lights etc.

Has your local garage checked the CU for faults and looked at the measuring blocks to see that what the CU is reporting is plausible?

Fuse 14 covers:

Interior lighting, central locking system, interior lighting

(without central locking system)

Presumably this is the power supply to the CU, so very much like restarting a computer, removing and reinstating the power to the CU will reset it.

I am of the opinion that you may be looking at multiple problems, one with the CU for the door switch problem and another for the remote locking. I suspect that the remote locking may be a broken wire in the multiplug to the drivers door control unit, the yellow/red wire that usually breaks very close to or within the plug, disturbing it during the lock change may have moved it enough to make contact for a while. This multiplug is also known for holding water and rotting the pins off the door control unit.

Even if you replaced the CU you won't know it has sorted your remote locking until you program your remote to it.