loose wire!

Hello - I am a relatively new owner and user of a defender 90 and in looking under the bonnet earlier I noticed a disconnected wire - not sure if I did it in trying to reach the back end of a bolt nut (of the headlamp screens) - does this do anything - I couldn't see it in the Hayes manual

Hello and welcome, you've posted in the introduction part of the forum and normally posts like yours asking for advice are ignored. However, I'm also a tratter owner so you have my sympathy.
That is an aftermarket temp controller almost certainly for an aftermarket coolent cooling fan.

welcome aboard

Hello and welcome

Hi and welcome!

Best posted in the 90/110 section for answers. But yes, it looks like an aftermarket temp controller for an electric fan. I’ve got similar on my 90.