Main beam will not switch off

Hope some one will be able to help.
Noticed at the weekend that the main beams were on when I locked the car up. the car is a 1.4 petrol 03 plate without driving lights
I checked that all the lights were in the off position on the stalk. and with no key in ignition. dipped beam and side lights were in off position, but the main beam was still on.
I have tried various things
disconect the battery and reconnect and the lights go off. lock the car with the remote control and the lights come back on.
If I disconect the batter and reconect and the lights go off, open a car door and the main beam comes back on
Removed each main beam fuse in turn and one side goes out, but other remains on.
Cleaned the contacts in the engine bay fusebox,
There is no diagnostic codes showing at present.
My thoughts are on a short somewhere, but where to look?
At present the only safe way to drive not dazzling drivers is to keep both fuses out

Any help would be greatly appreicated.
Chris

Hi Chris,

According to my diagram, the main beam is switched by a relay in the fuse box under the bonnet (engine bay fusebox), this would be worth a look.

The step after that, if the relay turns out to be ok, would be a look at the 'switches under the steering wheel' or the com2000 or the unit that has the light switch on it. They are all the same thing, but are given different names depending on who you talk to.

The relay for the main beam which is in the engine bay fuse box must be controlled in some way by the switches under the steering wheel, but I can't currently see how. I will dig a bit deeper to find out.

Agree with C3driver52, headlamp control is from the relay/fuseboard under the bonnet. It looks like there is a feed from the ignition so this should prevent the headlights being on when the ignition is off. The actual switching is done by the BSI (Built-in Systems Interface - Main control box for the car), it reads the switches and send signals along the data bus.

I would say a faulty relay is the most likely candidate followed by a wiring short. It would be worth taking the relay out and checking if there is power to the coil when the lights should be off, one side of the contacts should be permanently live, the other side should be volt free when the relay is off (will show as chassis/earth as there is a circuit through the bulb).