///////////// just bought a 1990 4 dr. with the Caprice Chassis but the A/C main dash vents and defroster do not respond (they remain in the park position). I bypassed the Avant labeled control module with a jumper piece of hose and everything responds (didn't check the heater water valve). So it appears to be electrical but I do get 4.5 volts or so to the control solenoids. Does anyone have any suggestions before I pull the radio heater dash cluster apart? Do the controls and solenoids operate on a reduced voltage or can I apply 12 volts to test them? Don Lindner////////////// --------------- On the 1990 faulty A/C system. The electronic controller is a weak link. It can be found in late 80's, early 90's Pontiac Grand Prix. The default program for the air is to blow thru the defroster vents. The system uses simple algorithyms to determine whether air should blow to the floor or through the dash vents - if a higher temp is selected, it's supposed to blow through the floor vents. My electronic control began randomly selecting the dash or floor and I seemed to have little control. The factory wants $350 for a new one, so I bought a used one. Had trouble with that one too, so I tried to adapt a 93-95 Grand Prix controller, but the plug in was different and overwhelmed me so I bought another used controller the same as that came in the car. This seem to have fix my issues - hope it stays that way. I've also replaced the heater blower motor and IC controller for the blower motor (mounted at the top of the blower box in the engine compartment). I understand there are solonoids that control the flow of air (floor, dash defroster) that the electronic controller activate. Don't think I've had problems with them. Good luck, Rich Richard Morris Renton, WA Cell: 425-417-5556 1964 Avanti R-1 #5367 1990 Avanti 4-door #78