Fun with 45 year old wiring

[Docsmitty]

I’m trying to troubleshoot the trunk popper and install a LED 3rd brake light, so I’m looking for the green “30” constant 12v line in the trunk. It appears to have been connected to this thing, along with a single yellow wire. I need to replace my multimeter so I’m not sure that the input is working, but want to see if removing this fixes it - just don’t know what this is.

Any idea what this is and if I can strip it out?

 

[Jack]

Looks like aftermarket relay probably for power antenna or an alarm ? But I’m just guessing

 

[dl242gt]

It's def a relay you aren't using anymore. So it's safe to remove. It should be getting a constant power and switched power wire depending on the accessory wiring it used to go to.

 

[Docsmitty]

It is mounted right next to the antenna, which is not a power unit anymore. Thanks!

 

[Docsmitty]

Seems like that relay wasn’t the issue. Is there any shortcut to chasing bad wiring? Feels like I’m about to dive down a rabbit hole. At least most of the interior is out