63 AC controls

[Zimm63]

Back at making my AC work the way its supposed to.    

 

Regarding the door controlled by diaphrams 1 & 2 that directs air from the fan either through the heater or the evaporator.  It appears to be spring loaded to cause air to flow to the heat side, absent the diaphrams pulling it the other way.  Question is how strong should that spring load be?  Moving it by hand, it seems like it takes considerable effort to open it to the AC side and keep it there.   It will snap right back when I let go.  

 

Is that correct, or do I need to figure out a mechanical problem before diving deeper into the vacuum switches etc?

 

 

[KongaMan]

That's correct.

 

Free advice (which is worth what you paid for it): Take the blower box apart anyway.  After 55+ years, it could probably use a good cleaning and lubing, and it's probable that internal seals have degraded and you have leaks galore.

[gungeey]

hook a mitivac handheld vacuum up to them see if they hold

[Zimm63]

Blower box comes apart from the engine compartment?  

 

Oh boy, another adventure.  Hope this one doesn't spiral like the stinkin center bearing. 

 

 

 

 

[Jim Cannon]

13 hours ago, Zimm63 said:

Back at making my AC work the way its supposed to.    

 

Regarding the door controlled by diaphrams 1 & 2 that directs air from the fan either through the heater or the evaporator.  It appears to be spring loaded to cause air to flow to the heat side, absent the diaphrams pulling it the other way.  Question is how strong should that spring load be?  Moving it by hand, it seems like it takes considerable effort to open it to the AC side and keep it there.   It will snap right back when I let go.  

 

Is that correct, or do I need to figure out a mechanical problem before diving deeper into the vacuum switches etc?

 

 

 

That is correct. It's a pretty strong spring holding the door toward heat with no vacuum applied.

 

That is why, when you are driving down the road with he A/C on and you hit the gas hard, you lose vacuum and the air starts blowing out on your feet. Then when you take your foot off the gas, the air jumps back to coming out of the dash outlets again. This is a '63 problem. Later years added a small vacuum reservoir to provide a reserve supply. I suggest you add a vacuum reservoir can to your '63 system.

 

These vacuum diaphragms have considerable pull, due to a pretty big diaphragm area. Assume 3 inch diameter, that makes the area pi*D*D/4= 7 sq. in.    So every 1 psi of vacuum on that diaphragm gives you 7 pounds of pull against the spring.  Our engines easily give us 20 in. Hg of vacuum, which is 10 psi (1 in Hg is about 0.5 psi) so your little diaphragm can pull up to 70 pounds force.

 

I have found that the vacuum switches leak vacuum a little bit all the time and don't seal well. A quick shot of spray silicone lubricant into the ports of the switch, and then operate the switch with your fingers repeatedly, will get them working properly again. 

 

You will really want to get a little hand-held vacuum pump, if you don't already have one, to troubleshoot everything piece by piece without having to run the engine. Plug lots of lines with golf tees at the start, to eliminate potentially leaky components, and start tracing the operation of the controls with a vacuum gauge. Then connect components after you have confirmed they don't leak.

 

A little detail on the upper diaphragm unit: Apply vacuum to the outer port to get 1/2 travel. Apply it to BOTH ports to get full travel. If you apply vacuum only to center port, it will act like it is bad (leaking) when it is not. Vacuum must be applied to both ports.

 

God luck.

[1965rivgs]

There should be a small cylindrical metal vacuum check valve on the `63 manifold, no?

Tom Mooney

[Jim Cannon]

1 hour ago, 1965rivgs said:

There should be a small cylindrical metal vacuum check valve on the `63 manifold, no?

Tom Mooney

 

Yes, Tom, there is. And on the new vehicles, with no little vacuum leaks anywhere in the system, the vacuum held and all was good. But on a 50 year old car with a little leak here and a little leak there, the vacuum bleeds off pretty fast.  A small reservoir provides a little more time before all the vacuum is gone.

 

[telriv]

The small reservoir Jim is talking about is used on '64,'65 & I believe '66 cars on the r/fender well which can be added to the vacuum check valve on the manifold which will supply the much needed reserve nec. to keep things operating properly for a longer period of time.

[Jim Cannon]

19 minutes ago, telriv said:

The small reservoir Jim is talking about is used on '64,'65 & I believe '66 cars on the r/fender well which can be added to the vacuum check valve on the manifold which will supply the much needed reserve nec. to keep things operating properly for a longer period of time.

 

Yes, I got mine off of a '64 parts car. Easy to add to the line between manifold and control valves. Adds some storage, otherwise does not change the way anything works.

[R8RS]

I bought a 64 last August, and the seller told me the AC blows cold, so I tried it and it did.  Then I noticed while driving with that nice cold air coming out the dash outlets, I had hot air blowing on my backside from the air outlets at the rear center console. How does one fix that issue?  

 

[abandg]

Close the heater control valve on the passenger side inner fender. It is probably open or stuck open. 

[Zimm63]

Thanks all.  I will figure this out, just need to allocate some time when I can get at it.    I have some used as well as new parts to go into it as needed.

 

Gene- would you happen to have one of the vacuum tanks in your stash?  Could pick it up when I come up for the trunk boards and signal/tilt stalks.  

[Zimm63]

OK.  Spent some quality time with my Miti Vac and the shop manual.  Found the #1 switch bad and fixed that.  Found both #3 and #4 diaphragms did not hold vacuum.  Plugged those lines and the air now comes through the dash vents when the cool lever is moved in.   

 

From reading old threads, those diaphragms are hens teeth.   It appears the fix is to install one of Old Air's replacements for 1 & 2 and T both lines into one.  

 

Question is:  Am I better off to have the recirculation door fully closed when ever the AC is on, or only when at Max?  If fully on, the line to #3 would be the source of vacuum to the T, I think.  If only at Max, the line to #4 would be the source.

 

Have I got this right?  

 

How hard is it to replace the #3 & 4 diaphragms?  I haven't gone under the car to look yet.  

[Jim Cannon]

I recirc all my air when A/C is on because the A/C unit is marginal on a 1st gen. Riviera in the hot summer. Closed (recirc) is the result of no vacuum to either diaphragm. Original Buick design always had partial fresh air coming in, even on Max. cooling.

 

I take in 100% fresh air when A/C is not on.  Otherwise the car will fog up in the winter.

 

Get a double diaphragm from a parts car.  Or that replacement unit.

 

Kind of a pain to replace. Similar to the dash unit (diaphragm #1/#2).Work from below.