Engine loom...what's this plug for?

[Jamz3k]

Doing an engine swap and can't for the life of me figure out what this plug on the loom is for.... it's driving me crazy.  Hopefully someone here can bring my sanity back.

(It's the grey one sitting on top of the intake manifold)

[SteveJ]

Air-con compressor clutch control.

[Essex2Visuvesi]

Air-con compressor clutch control.

Yep I concur
To confirm it exits the loom at the same place as the cables for the alternator, which it looks like in the top picture

[Carolyn]

Now is a great time to put a new thermostat in, clean out the oil control valve filter, check bearings in alternator - all piggy jobs once the engine is in.

[Essex2Visuvesi]

Now is a great time to put a new thermostat in, clean out the oil control valve filter, check bearings in alternator - all piggy jobs once the engine is in.

I'll second that suggestion
The alternator is easy if your day job is proctologist