on one of my vettes (1988) on the passenger side in the engine bay is the like a/c box and the heater core box and the 2 hoses going threw the firewall to the heater core, well right before they enter the firewall, teh one has some kind of solenoid on it that seems to be vacuum operated. that vacumm line wasnt hooked up to anywhere and i need to find up where it hooked up to, i cant find a t or vacumm line or anything anywhere thats not hooked up. its just just this one, no extra ports or hoses anywhere for this to connect to. maybe im not looking harfd enough or it was just never hooked up, can someone let me kno where that should connect too or where to look for it to connect to? thank you

 

That's your heater control valve. It shuts off water to heater core when a/c is on and vacuum is supplied through the a/c control head.