I have a 94 grand am that the defroster quit working on. I tore everything down and found that there is no vacuum to the head unit. I believe there should be a main vacuum in and then the switch ports it to the appropriate actuator in the distribution system.
Does anyone know where the main vacuum source is or what faulty component I should be looking for? I've looked and listened under the hood and don't see anything along the firewall or the manifold(not to say I didn't miss it!). Everything under the dash looks to be in good shape.
Thanks
Chris