Does anyone know why, on my '90 SR5 4x4, the headlights would have what appears to be an extension or adapter ??
I had the right lamp burn out and just replaced it. When I removed the old one I found what appears to be an extension between the main harness and headlamp that looks factory and don't know why it would be there.

 

I have seen adapters used between the factory plug and the headlamp for running a trigger line from the Hi-Beam to drive a spotlight relay.
I bought a lightbar that came with had an adapter like that.
If there is no wire running of the line - just a straight extension, and the standard plug reaches the headlamp fine - then i don't know why.