Just tinkering with the speedo assembly/binnacle today and suddenly I was aware that the headlights were on.
Ah, I must have hit the switch. Turned it off, but the headlights are still on. The taillights are not, the side lights are not.
Went back through what I was doing on the car up to when I noticed the problem, but I have not been able to correct the fault.

Here is what I was doing up to that point;
-I gave the front left of the engine bay a bit of a jetclean, just where oil had been spilt by previous owner. Water may have got to the rear of the lamps?? I can't see that happening though.
-Took off the steering column shroud and the panel underneath the column, to get at the four bolts holding the instument cluster to the dashboard. Didn't remove the cluster though, bolts too long for a socket.
-Put it all back together.

Now the headlights stay on dipped. Main beam will work, I can turn the side and tail lights on too. It's just that the dipped lights stay on even without the keys in!

Anyone ?

Do they go off on their own after around a minute if so you have the delay turned on.

Water from the jet wash in the fuse box?

It's a 1988 Classic, so I am not sure it has a delay for the lights and they stay on all the time.

Water in the fusebox is a possibility, but I only jetted a small area at the front of the car, can't see a fusebox there.
Risk of sounding like a complete numpty, but where is the fusebox on these cars?

Partial answer from another forum was to unplug the voltage transformer under the dash. This seems to have constantly been supplying + battery feed for the left and right headlights - hence always on.
This has provided a 'fix' but has not solved the problem or why it happened and I am not sure what damage may be done by leaving this unplugged.

If anyone knows if it is OK or not to leave it unplugged, let me know?

Had the same problem on my 89 classic, the thing you unplugged is the dim/dip relay its not a problem to leave it unplugged . If you open it up chances are you will find couple of dry joints on printed circuit, few minutes with soldering iron and its back working, had same thing with older astras and cavs which use same relay (its behind ashtay on astras, cant remember where on caviliers think its same place).

Thanks.
I read about these dim/dip things but thought they operated the dipped headlights at a low output when the sidelights were on. Don't remember them doing this on the car though?

I might have a look at it if I have time but if it isn't really needed, maybe I won't.

I have just dealt with the same problem. You can leave the dim dip unconnected or repair. Not being clever with a soldering iron I have purchased a replacement from ClassicLSE in Kent at £17.50 delivered. I am sure there are other RR breakers about who will supply. They will need to know the colour of the plastic plug as there are 3 different types.