1968 Buick Skylark Vacuum Diagram for A/C

**jaw0001** · 12-12-2015, 06:21 AM

I have ripped my car apart to fix a no-defrost problem. This includes taking the inner (& outer) fender off and replacing the blower motor. Now it will not blow air up to the defrost. So I took the heater/AC box out and found that the twin diverter doors were in need of some freeing up and did that. Wanted to make sure that all vacuum was working before putting box back in. But there are a lot of them and the vacuum coming from the canister on the firewall is weak. Does someone have the appropriate vacuum diagram they can send me? Or can someone verify which manual this diagram is in (obviously would prefer an image)? Or just some general wisdom born of experience? Thanks.

**Bob** · 12-12-2015, 08:51 AM

Here you are: http://www.teambuick.com/reference/l...files/13-a.pdf

**jaw0001** · 12-12-2015, 11:44 AM

That's awesome. Thanks a lot. Will post my success. Merry Christmas!

**BluesBrothersBuicks** · 12-13-2015, 05:01 PM

Originally Posted by jaw0001

That's awesome. Thanks a lot. Will post my success. Merry Christmas!

Be sure to check the vacuum canister for pinhole leaks. This happened to me. The holes are usually at the crimped seam on both ends of the can. See if the can will hold a vacuum. If it doesn't - then you have a leak and you won't have enough vacuum to operate anything under the dash. Just smear silicone around all seams and let it cure. This procedure solved my problem. Good Luck!! BluesBrothersBuicks

**jaw0001** · 12-14-2015, 05:46 AM

I did notice that there is precious little vacuum coming out of the vacuum canister (round ball on firewall), but plenty going into it - stock 250 6 plumbed to manifold under carb base (not ported vacuum). I tried to plumb directly to vac source (bypassing canister) at idle and didn't fix problem. But I will look into it. I broke the stub going into the ball from the engine trying to pull the vacuum line off. Epoxied it back in. How dare a 50 year old piece of plastic break! I assume the canister is there as an accumulator for low engine vacuum situations (for instance WOT)?

**jaw0001** · 12-14-2015, 06:20 AM

I thought I posted a reply to this, so if it pops up twice forgive me.

I accidentally broke the to-engine-barb off the vacuum canister (round ball on firewall) when trying to pull the hose off and had to epoxy it back in (basically filled the hole and pushed in the barb and drilled a hole after it cured. I did notice there was precious little vacuum coming from the tank but plenty going in. I assume the tank is an accumulator for low-vacuum situations like WOT. Hose goes to intake manifold under carb, not ported vacuum so should be good. I tried plumbing it directly at idle and see if it works but did not. I need to buy about 10 feet of new hose and start testing things. But there is no harm in siliconing up the vacuum tank / canister / ball since I already butchered the looks of it. Thanks.

**BluesBrothersBuicks** · 12-14-2015, 02:11 PM

Originally Posted by jaw0001

I thought I posted a reply to this, so if it pops up twice forgive me.

I accidentally broke the to-engine-barb off the vacuum canister (round ball on firewall) when trying to pull the hose off and had to epoxy it back in (basically filled the hole and pushed in the barb and drilled a hole after it cured. I did notice there was precious little vacuum coming from the tank but plenty going in. I assume the tank is an accumulator for low-vacuum situations like WOT. Hose goes to intake manifold under carb, not ported vacuum so should be good. I tried plumbing it directly at idle and see if it works but did not. I need to buy about 10 feet of new hose and start testing things. But there is no harm in siliconing up the vacuum tank / canister / ball since I already butchered the looks of it. Thanks.

Yes, I did the same thing - plumbed directly to engine vacuum and I had the same result - still wouldn't work. I thought your vacuum canister would be a sheet metal "can" - guess not!!! I apologize. I know the round "ball" that you have mentioned - just make sure to take care of all leaks. BluesBrothersBuicks

**jaw0001** · 12-30-2015, 09:11 AM

Thanks for the replies. Here is all the things I did.

Took off outer passenger fender, inner passenger fender (did not suck down AC to temporarily remove the hose - hah), hood. Replaced the blower motor (old one barely blew). Removed heater box. Cleaned up corrosion and dirt from an evident prior heater core leak. Free'd up main diverter door (not the defrost door, the big door) with some WD40. Fixed cracked hard ducting. Replaced 45+ year old 2 3/4" ducting (they carry it at O'Reileys, not at AutoZone, not at Advance Auto Parts). Siliconed up vac can per suggestion (not sure it needed it). Fixed one broke tab which mounted the defrost door control cable to the heater box, Cut 1/2" off and reattached about 4 vac tube ends which were leaking. Fixed. One thing I did for troubleshooting was bought 12' of 3/32 vac tubing to test both vacuum actuators for proper actuation prior to re-assembly. Thanks for the help!