In article ,
Kaz Kylheku wrote:

Would a bit of napthalene mothball keep spiders and other small creepy
crawlers out of the warmth of an always-on, so warm, bit of kit, or any
better ideas to keep bugs out of there.

Napthalene smells like **** and is a poor insecticide. It's used
in closed spaces where the concentration of the vapors builds up.

And, both acute and chronic exposure to it can do Bad Things to the body.

I'd spray some permethrin-based insecticide in the vicinity,
and maybe even inside the unit.

The stuff is available in the form of bug spray which contains only
around 0.25% of the stuff. It leaves no visible trace and the sprayed
areas stay effective for weeks to months.

Spraying the inside of the case might be sufficient.