Defrost Vents

[live4theking]

Howdy all,
I've finally got my box all put back together, but I'm having a heck of a time getting the doors to open and close properly. The fresh air or recirculating door works fine, but of course it's on it's own actuator.

The doors for the heat, ac and defrost are operated on linkage that connects them together. I guess my question right now is how far are the round defrost doors supposed to open.
They barely open. This is one of the ducts I'm referring to.

 

[bigmoparjeff]

I think they should open a full 90 degrees. That linkage is a bit complicated and it may take the correct combination of vacuum pods to get it to work correctly. I'll try to take a look at one of my HVAC boxes in the next day or so and see if there's any trick to make it work.

Jeff

 

[bigmoparjeff]

The defrost doors do open fully.

The A/C door has to be closed first before the defrost doors can open.

Jeff

 

[live4theking]

I believe that you are correct in how far they should open. If you could take a picture or two like the ones below I would greatly appreciate it.

@Trace 300 Hurst do you have any pictures of the linkage from when you did yours?

 

[bigmoparjeff]

I can do that if @Trace 300 Hurst doesn't have some pics ready to go.

Jeff

 

[Trace 300 Hurst]

Hopefully these may help.

Have you applied vacuum to the hoses (and dashpots) using something like a Mighty Vac to see if they work? I did a lot of that to observe the action.

 

[Trace 300 Hurst]

A few more...

I don't know if your box is on the bench or not. But regarding vacuum, I also rebuilt my switch and bench tested it.

View attachment 489593

 

[bigmoparjeff]

Looks like yours is a fusey box.

I should shoot some photos of a slab box just in case the linkage is different.

Jeff

 

[live4theking]

@Trace 300 Hurst thanks for the pictures. Unfortunately your set up is completely different. I do have the box on the bench and I've been using a Mityvac to test it.

 

[Trace 300 Hurst]

Looks like yours is a fusey box.

Yeah, I'd say it's probably a fusey box.

 

[Trace 300 Hurst]

@Trace 300 Hurst I do have the box on the bench and I've been using a Mityvac to test it.

Have you tested the pots without being hooked to linkage, just to make sure they work and hold vacuum? (don't over-suck them!!) In my case, my "double pot" for the "open or closed" recirc box on the passenger side only worked nicely in one direction, that being the fresh air mode. So I left that hose disconnected and locked the box into recirc only, which is what I want when I have the AC on. The old-ish weatherstriping allows enough damn fresh air in, anyway.

Permanently set in Recirc mode, no fresh air:

 

[bigmoparjeff]

Photos. This is a 1966 box, but is probably the same as '68.

Jeff

 

[live4theking]

@Trace 300 Hurst yes I have actuated them with the mityvac without them hooked to anything and they seem to be fine. I have notice that both of the actuators in question seem to pull the rod back better than pushing it out.

Jeff - that box looks to be almost indentical to mine. Thanks for all of the pictures. Now I can compare to make sure that I've got the linkage installed correctly.

 

[Trace 300 Hurst]

@Trace 300 Hurst yes I have actuated them with the mityvac without them hooked to anything and they seem to be fine.

And they hold vacuum? I ask, because if they don't, they could be a "weak suck" to move the actuators. Do the various doors move freely and not bind when not hooked to the pots?

 

[live4theking]

I've been working on my heater / AC Box for what seems like an eternity. I've got the box reassembled now, but I'm unable to get all of the doors to move via the actuators.

The other night I was attempting to test my diaphragms with a Mityvac and a gauge inline.

Since my motor makes 15-17" of vacuum I applied 15" through the hose harness. The only diaphragm that was connected during the testing was the one for the recirculating door which has worked fine all along. I applied vacuum until the rod was either fully extended or retracted and then continued until 15 " was indicated on the gauge, with the exception of the Heat / AC Door in the extended position. The time that is indicated is how long it took for the vacuum to bleed off to the next level; 15 to 10, 10 to 5, 5 to 0.

Is this normal operation?

 

[Trace 300 Hurst]

That doesn't sound normal to me.

Is there ANY chance that the bleed restrictor has been improperly reinstalled into your spaghetti of hoses? Or that bleed has become plugged?

 

[bigmoparjeff]

Those vacuum actuators should not bleed off at all. Theoretically, they should hold vacuum forever. Despite that, your listed bleed off times are pretty long and the engine should have no trouble providing enough vacuum to compensate for the slight leakage you have.

I had to replace one of mine back in 1983 because it failed completely and wouldn't move the linkage at all it was leaking so bad.

I don't think your actuators are the problem.

On Sunday I'll use my Mityvac and do some testing on the HVAC box to see if I can come up with anything that might help.

Jeff

 

[bigmoparjeff]

I got the old Mityvac out and plugged it into each port on the main connector that goes to the control head. There doesn't seem to be any special trick to get the doors to open and close.

One thing that I did notice is that the defroster doors are slightly open any time the A/C door is completely closed. When the A/C door opens, the defroster doors shut the rest of the way.

You must have something that's binding or your linkage isn't set up 100% correctly.

Jeff

 

[live4theking]

I got the old Mityvac out and plugged it into each port on the main connector that goes to the control head. There doesn't seem to be any special trick to get the doors to open and close.

One thing that I did notice is that the defroster doors are slightly open any time the A/C door is completely closed. When the A/C door opens, the defroster doors shut the rest of the way.

You must have something that's binding or your linkage isn't set up 100% correctly.

Jeff

Thanks for checking.

 

[live4theking]

That doesn't sound normal to me.

Is there ANY chance that the bleed restrictor has been improperly reinstalled into your spaghetti of hoses? Or that bleed has become plugged?

View attachment 490079

View attachment 490080


View attachment 490078

I don't have the vacuum reservoir or the bleed that you pointed out.