Hi All, My 68 California GS has a cranky vacuum system. Not getting any air flow out of the dash vents. Recently replaced both the AC/Heat/Vent/Rec. thumbwheel switch and the heater blower thumbwheel (both NOS) including a NOS master vacuum valve that attaches to it. I Used a vac. guage starting from the port on the rear of the intake manifold, through the vac. reservoir and to the heater control valve and all was ok. Had vacuum going into the master vac. valve but nothing coming out so I replaced it with the NOS unit. Everything is back together, and I still can't get airflow out of the dash vents. Noted when I had the AC/Heat/Vent/Rec. switch out that there are 4 ports on it. The 68 Skylark shop manual only shows 3 vac. lines coming off of it, not only for my application, but for all the other series included in the manual. The schematics don't show the 4th port either. The old switch I took out had 4 ports, so does the new one. Anyone have any ideas?? Everything that works off of the cables (defros and temp control) is working. I can switch the air flow from the bottom floor vent to the defrosters. Just can't get any AC air to the dash. The main entry door behind the passenger side kick panel is fully open and there is no vacuum there on either line. I've checked the vac hoses and am quite sure that they are hooked up where they're supposed to be. Thanks. Tonino
Bolding mine. That door is used to switch between inside and outside air, so you may want to look at that a little more closely. I just put AC in mine, but haven't gotten it all hooked up. Also, I dog-robbed the whole system off a '69, though the only difference I can see between '68 and '69 is that the thumb wheels (which I despise) are '68 only.
Thank you for the reply. I shoehorned myself under the dash yesterday to find that there is a small manifold that all of the vacuum lines to the AC/HTR/VENT/REC switch connect into. The manifold then plugs directly into the back of the switch. I have everything working now with the exception of the main air entry door. There are two vac. lines from the manifold to the vac. motor on the door. One is reading solid vacuum at 15, the other - regardless of switch position - is only reading 1. I'm going to pull the line and blow it out to see if there is an obstruction in it. If its clear, next will be to remove the manifold itself off the switch to see if the port is obstructed. If the manifold is damaged internally, the manifold should be a replacement item, but I haven't seen any anywhere on the internet. Will have to check a parts list to identify it correctly and look again. If anyone out there has a parts list for a 68 Skylark w/AC, I'd be forever grateful if you could pass me the part number and correct nomenclature of that little manifold. Thanks Tonino
