I've just installed some new headlights(TYC) in my VL, I did disconnect the battery and headlight looms to carry out the install. The problem I am having, and you'll probably need a wiring diagram for this, whenever the car is running (has to be running) and the interior light is meant to come on, ie door opening/adjusting dimmer switch to full bright, the horn goes off. The only point when the main interior light comes on, and it is only momentarily, is when switching between high/low beam. Prior to installing the lights everything worked as advertised. For what it is worth after the install I found my high beam fuse had blown, it has now been replaced. Can any guru's shed some light on this?? TIA

The issue sounds unlikely to be caused by installing new headlights but to rule this out unplug both headlights and see if this fixes the issue, otherwise check all the fuses in the fuse box to make sure they aren't blown and also check the fuse rail for melting which is common in VL's and may be causing a dodgy connection. Next I would try the indicator switch with another one and see how you go. Also check all earths around anywhere you worked on.