KJL

I am trying to trouble shoot under dash vacuum leakson my 72 L48 and I am sure some of the plenum actuators will need to be replaced. I have found that the under dash area is not a friendly place. I have an assembly manual which helps with the indentification of the many vacuum hoses but does little to help you fugure out how to get to the various components. I recall in a Vette magazine a while back they did a complete AC rebuild. I am only interested in getting mine fuctional.

Gary79

TTT, anybody?? i could use this as well,as my windshieild defroster quit over a year ago.

mrvette

OK, here we go, this job is a pain in the axx, but simple, really...
my car was put together with all phillips screws....but someone could have changed that...anyway, pull the front two passenger sill plate screws, slip the kick panel out from under the alouminum...pull the add on plate on the console up front/side...one screw, pull the two screws in the door jamb holding the map pocket piece in place, there are supposed to be 2-3 screws going laterally into that map pocket fron the center instrument bezel, pull them.... and then the 3 top screws into the dash panel....now carefully remove map pocket assembly....
now you can take the screws from center bezel into tach/speedo assy out, then the one up top and the two under the wiper switch going into the vent assy....that releases the wiper controll assy.....it unpluggs.....
now the rest of the cluster should be easy, there are two small bolts, about 3/8-7/16 or so up under the console, best accessed by pulling consold shifter plate...4 screws and shift ****.....these two bottom nuts are on studs coming out of the center bezel....up under the metal support for console trim plate....I never bother to replace those bolts, or the side bolts into trim panels either, everything fits and rides fine on my car...just makes things simpler....
at any rate the center cluster has an oil line to the gauge, undo it, and unplug the electricals.....now that is out of the way.....
at this time you may be able to see the entire operation of the a/c ducting and all the dash pots, except one......

but before you do all that, as I did, .....snicker....try looking at the two dash pots in the vent returns....the one up top under the wiper door, under the fender and the one inside behind that kick panel....the rubber dries out, and so there are no replacements....ME, I just seal the outer upper door shut with RTV, and remove the inner door assy entirely, plugging the vacuum control lines with nails....it's in constant recirculate mode then.....good enough considering the air leaks and lack of a/c power/hot feet syndrome we shark owners have to put up with....

GENE

KJL

Gene,
Last night I removed the blower motor/fan figuring that is where I would find the second recirc dash pot and there it was. There are some companies that are making replacment under-dash actuators but this bad boy seems impossible to remove. The vacuum line is also a 2 pc connection through the plenum door. The dash pot is mounted to the door and I bet my bottom dollar that the leak is at that funky connection. Anyway.... I checked the other actuators with a vacuum tester purchased at Sears. I checked them at the console where the color coded vacuum lines connect to the selector switch. It was quite easy knowing from my assembly manual what color line goes to what dash pot. I had to isolate the recirc (pass. side kick panel and upper fenderwell) dash pots for they both run off the same line. When checked separately I found they were both shot. The other two where good.

So I basically came to the same conlusion as you and thought setting them up in recirc mode would be best and plug the lines. To do this I removed the return spring from the kick panel dash pot but how were you able to RTV the upper door? It seems to be spring loaded but I cannot see any springs? Is the spring in the dash pot? Should I remove the cotter pin from the rod and disengage the actuator rod to release the tension? did you just smear RTV around the edge of the door with you fingers and wedge the door shut until the RTV set up? Do you know of another way to access that actuator? I can see it through the wiper door but would have to remove door and door linkage to have any chance of getting a couple of figers on it. I can get one hand on it though the fan hole but can only see it with a mirror.

Thanks for your help!!

mrvette

KJL, you the spring is in the damn dash pot assy...I pulled the 2-3 5/16 bolts and removed the whole door assy, you have to have the entire WSW apparatus removed as well as vent grill, obviously....so upon diaabling my door junk, I jammed a small screw in the flapper and wired it shut to something in the wiper area, then took RTV on my fingers and sealed it from that side....messy job, then inside just removed the flapper, plugges all lines and had done with it....the dashpots on both assy...seem to fail internally...diaphragm....

GENE

KJL

Gene,
I am going to try to pull the cotter pin to release the dash pot actuator rod from the arm. This will release the spring tension, then I will spread around the edge of the door some RTV and wedge is shut. I think I can do this through the fan hole with a mirror and long needle nose pliars. Now that you have confirmed for me that the spring is in the dash pot, my idea just might work. I really want to avoid pulling the wiper stuff. I will let you know how it goes. Thanks a bunch!!