What wire goes to this ?

[Marvan c10]

 I found that the wire for the Temperature Sensor was plug to it, looking at the Engine wiring Diagram here I can't find it.
 http://forum.73-87chevytrucks.com/smforum/index.php?topic=11766.0

[rsandusky]

There should be a dark green wire going to it. That is the idle kicker solenoid for when the air conditioning is turned on to increase the idle speed for the additional load. The connector that goes to this should have a tab and release lever so that it doesn't get disconnected accidentally.