Heater A/C controls

[blown motor]

My 74 had A/C but it's removed. In the first picture is the 3 pronged plug the fan control? And what do each of the other two spades control, they must be A/C.
On the vacuum plug there is a line with a red tracer, a white tracer and a yellow tracer. What are each of those for? What is the little white "bulb" in the line shown in the second picture. What does that line do? I have the push buttons set on defrost but most of the air is coming out on the floor so the box seems to be in the Heater setting. This is the issue I need to solve. At the very least I want that to be on the Defrost setting in case I get caught in a rain and the windshield steams up. That may have happened once before. @BIGSHCLUNK

[blown motor]

Oops, forgot the pictures.

[jimynick]

Murray, I think that white thing is a one way flow control valve. As for the rest, I haven't a clue. Good luck buddy! 

[Mr Cuda]

Check valve, check.  All the vacuum lines are color coded to a location.  Shop manual time. They don't usually come loose, but you could have a bad vacuum pot. Some have vacuum on both sides to operate.
From my long ago A/C experience,  I thought the default position was defrost. The electrical connection is rather melty, so you probably need a new push button controller.
I've heard of them being rebuilt so don't haphazardly take it apart.
The fan speed switch  is tied into the A/C harness to get the  max fan speed. I was going to check if the other end of the red plug went directly to the heater box.

[blown motor]

@Mr Cuda  Yes the three pronged terminal is a little melty. It got a bit warm at some point in it's life, the plug also has some melting, and I feared further trouble so I pulled the plug off and used a jumper wire in it to give me high speed on the fan. This has worked fine for several years, I just can't change fan speed but who cares. The bigger issue for me is being able to change from Heater to Defrost setting.

[blown motor]

A further thought, is it possible the problem with not being able to switch to Defrost lies with the push button controller? Just thinking out loud. When that three pronged plug got hot could it have damaged something else inside that relates to the function of the pushbuttons?

[Mr Cuda]

I don't think so. Lack of vacuum,  or a bad vacuum pot.
 The pushbutton controller can leak internally,  but usually suffers from broken nipples.
 The picture shown with the red hose is a vacuum on both sides flapper and will stay put once moved. The others are spring loaded and pop back with no vacuum.
 I would have to get a dash plenum to know which air port feeds defroster 

[EV2RTSE]

I can't seem to find the post where this came from right now but I had saved this pic for reference-

[Mr Cuda]

According to that nice picture,  #2 is hose with white tracer, not one of the vacuum pots in my picture.

[blown motor]

@EV2RTSE Great picture, thanks. Am I correct to assume 8 oz (?) is the correct vacuum?

[EV2RTSE]

Yes I believe so, 8 (inches) of vacuum. 

[BIGSHCLUNK]

WOW, am I late to this party... Yes its an issue!