Thanks,
I found the unit although the wiring between the unit and the connector are different to the wiring diagram, no surprise there then.
I just unplugged the unit and I no longer have the dimmed lights or the large voltage drop shown on the voltmeter.
I've done a check of all lights and other electrical units and everything is working normally.
There are only 4 wires on the unit itself, white, black, red and purple. These don't match anything in the wiring diagram so I guess it is component from another vehicle or supplier.
Looking at the diagram the lights are on a duplicate feed so they don't rely on the feed coming via the dim dip module.
