Hi Again, I've been trying to get my ac vents working. I 've read alot of previous posts on this forum and have done diagnostics and got it working with a temporary kluge. i can say the vacuum systen is good from the intake manifold to the inside of the dashboard. I think the problem is in the ac selector control panel, my ac system is a MCC type the one with 2 sliding levers and a rotary switch for the fan. I've read both the volvo green book on ac system and haynes manual and i can't find a picture of the vacuum switches, their location or a part number find a replacement. does anyone know the part number. or how to repair the vacuum switch? I'm hopeing this part can be replaced or fixed without taking out the entire dashboard, I kluged a temporary fix by running a line from the vacuum line to the vent actuator so cold air will flow out of the vents until i get it repaired, Mike

 

what year is this 740 ? my 92 has the rotary selector controls for the fan and vents, and a couple buttons for AC disable, and air recirculation.

pretty sure the whole heating/ac control panel is a single part number and whats inside is 'black box'. and, hmmm, pulled up the parts diagram for a 1986 (randomly chosen) and its controls are as you describe, two sliders, and there's several replacable parts inside, including 2 different 'vacuum valves', parts 5 and 6 on this page, http://www.volvopartswebstore.com/sh...ssembly=236345

 

Yay! Pierce! You rock! mine is an 89 but the panels look identical. That is the only picture i have ever seen after googling the web trying to find a diagram or a part number. I'll bookmark that site for future reference. Thank you again, Mike

 

the catch-22 with that dealer site is, they don't index any models older than around 1995. I have the older Volvo "VADIS" parts catalog from circa 2003 on my PC here, so I look up the year/model car, find the parts on there, then enter the part numbers onto that site to find the equivalent diagram ... Also note, that site may well list a lot of parts which are in fact no longer available, you won't know until you try and order them. As the factory and Volvo USA runs out of inventory, they aren't making any more parts for these older cars.

 

I don't suppose there is a website with the old "Vadis" catalogues online? I found a website with the volvo green books online and i found a volvo Regina Rex fuel/ignition book on a different site. These are extremely helpfull. i've already googled both part numbers and have found several online for sale. not cheap but not a arm and a leg either. I'm willing to bet it is part 5 aka 1323744. I'll know better when i dive in to it. I was worried that the valve block was buried deep somewhere in the airboxes, but since it is on the back of the controls, i feel better in getting to it.
Mike

 

vadis is a cdrom that only runs on up to windows XP (so I run it in a virtualbox on my windows 8 system). you can find iso files of the cdrom lying around the usual places to find suspect software.

 

cool, i run linux, but i'll look into a windows emulator, and see if i can find a copy, again thanks for the info, Mike

 

That panel is super easy to get to and get out. Just pop the bezel around it and there are some screws that hold it in. Then you can examine the whole thing for leaks, it's totally mechanical. Junkyards are full of these things--they rarely go bad.

 

Hello Again, I got the AC fixed, it turns out main flexible vacuum line feeding the controller had a clog in it. the main line has a splitter sending vacuum to a valve that controls the heater water valve and the other side goes to the controller to open air doors. The splitter is made out of clear "rubber /silicone" and i could see a black blob at the junction point. I cut that part out and couldn't blow air through it, so i made a new splitter out of vacuum line pieces from a local auto parts store. Thanks everyone for your help, Mike