A little help please.

[kevinr1970]

I searched this forum, but couldn't find the answer I was looking for. If someone knows of a thread that addresses this question please post a link or give me an idea of where to look.

So, in my '82 K5 2wd I get heat out of the vent in abundance. The problem is I can't get it to change over from the "vent" to the defroster or the heater. I thought I had read something here about what controls the ducts for the defrost/vent/heat (vaccum)? When I operate the switch on the dash, the cable moves the lever behind the dash, but I don't hear any thing change?
There is a "ball" shaped thing behind the A/C box that had a vaccum line that went nowhere and was obviously burnt from touching something real hot (like the headers?). On the engine I swapped into the truck there was a line I could not account for coming off the side of the carb. I thought it went to the ball thing on the other truck so I plugged it in there but nothing changed.
Does this thing have something to do with my heat/defrost/vent controls? And if so, where would the other end of it go?

[gchemist]

That thingy is the lockup switch for the torque converter.

[kevinr1970]

For the 700r4, or do I need to hook something up to it to get my TC to lock-up?

[Phuloi68]

I was having the same problem with my 85. I checked cables, switches, the plastic thing on the heater box(which someone said breaks keeping defroster door from switching). I spent alot of time putting my 6ft 1" 300 lb body upside down under the dash trying to figure out what the problem was to no success and kind of gave up. just kept rags to wipe the window.
I decided to change the carb.air filter. When I took the air filter housing off to look at the carb. I saw a rubber hose behind the carb broke off. It's one that comes off the tee fitting on the intake manifold(vacuum). I trimmed it and pushed it back on and I heard doors flopping, air gushing,etc. Now, my defrosters work so good I almost have to use hair gel to keep the few hairs left on my head from blowing in my eyes...
AND, I swear, the old beater is running better overall.

[kevinr1970]

So where did this hose go to? The intake manifold has a few fittings with nothing going to them, but was like that in the other truck and it ran good. It had fully functioning defrost/heat as well.
If you had a picture it would speek 1000 words

[60-66 Nut]

The "ball" shaped thing is supposed to be a vacuum reservoir for the a/c and heater controls in the dash. Normally it has two hoses hooked to it, one hose going to one of the 1/4" ports on the manifold tee, then the other hose is usually a small plastic line that goes through the firewall somewhere near the a/c evaporator box. Sometimes those plastic lines get hard and snap off, the one on my 83 GMC was broken off right at the firewall. I had just enough there to slip a piece of small vacuum/washer hose onto. Hope that helps.

60-66 Nut

[kevinr1970]

There is only one line coming of the ball? Sounds like a good place to check!

[Phuloi68]

The place where the hose was broke on mine was a couple of inches behind the carb on the intake manifold. it is a Tee fitting with several hoses coming off of it. I don't think you can see it with the air cleaner on. It's probably a 1/4 hose. I didn't pay any attention to where it went to but as soon as I pluged it back on things happened and it has worked fine since.

[kevinr1970]

I have a fitting on the back of the intake manifold, between the carb and distributor. It is not a "T" fitting (two fittings) but more of an upside "L" (single fitting). See retarded arrows.
I looked at my '81 Jimmy and it has a similar "L" fitting. The line from it is much larger diameter and it connects to I think a metal line sort of beneath and behind the distributor then goes underneath the truck on top of the tranny???

So I checked the ball thing and it does have a second plastic line that disappears through the firewall. I noticed on my '81 that the lines bypassed the ball thing so I tried this on my '82 and it did not change anything.

Finally, I was mistaken saying I had seen the cable move the lever. It was the hot/cold lever that was moving (behind glovebox). On my '86 diesel (no A/C) when I pulled out the ashtray assembly, I was looking right at the lever for the heater/defroster. On my 82 (with A/C) there is ducting behind teh ashtray assembly. How do I get to the lever to see if it is working or even hooked up?

[Phuloi68]

If you take out your glove box, you will see the first plastic piece for your air cond. ductwork. there are a couple of small screws holding it on. take them out and you can remove that piece and see the top of the heater box.
From what I have guessed from reading this board and other info about the defrosters not working, there seems to be 2 possible things that could be wrong. There might be other causes I am not aware of too.
Vacuum leak or some little plastic thing on the top of the heater box breaking.
With the fact that rubber hoses can get brittle as they get older and crack or break and they are easier to inspect then trying to see if that plastic thingy is broke, that is where I would look first.
The area behind the carb you marked was where my hose was broke. it came off a fitting I thought was tee shaped. it might have been L shaped, I don't remember. but it was a 1/4" hose and it was manifold vacuum.
I think you have a decal on the top of your core support that shows your vacuum lines set up.
As I am basically a shade tree mechanic i don't know of how or where to put a vacuum gauge on to see what you get. maybe someone on the board can be more specific as to where to test.
But from listening to others with this problem I would almost bet a donut it is a vacuum issue.
Hope you find it.

[86-C10-V6]

Not sure about the 82 model, but on my 86 there is a vacuum switch mounted in the same location that you are showing in the first picture you have posted. Looks the same to me, this is called a tip in vacuum switch and the vacuum line should be connected to the back of the carb just above the big vacuum line going to the brake master cylinder.
This switch senses a drop in vacuum and will cause the ignition control computer to retard the timing temporarly. Notice the wire to the switch passes through the fire wall and should go to the ignition computer module under the dash.
If you have bypassed the ignition computer under the dash or if you use an aftermarket distributor then you probably don't need this switch. There have been several threads about bypassing the computer module.

I believe the TCC vacuum switch for the transmission is mounted on the drivers side firewall.

I believe the change from heat to defrost is vacuum controlled under the dash.
Hope this helps.

[FLAGG]

I had an issue with my heater not switching to defrost when I bought it. Turned out it was a $5 plastic piece that connects the actuating rod inside the heater assembly to the flapper door that directs the air.

[jimfulco]

I had a '77 Nova I-6 that had the vacuum passage in the intake so coked up it wouldn't pass enough air to do much of anything for the heat/AC or the power brakes. It read 19" of vacuum, but there was less than a pinhole's worth of air passage. I took a drill bit to it (by hand) & got it working again.