A little help please. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

kevinr1970 · 01-24-2005, 03:02 AM

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 · 01-24-2005, 03:25 AM

That thingy is the lockup switch for the torque converter.

kevinr1970 · 01-24-2005, 04:18 AM

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

**Phuloi68** · 01-24-2005, 08:42 AM

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 · 01-24-2005, 12:16 PM

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 · 01-24-2005, 02:34 PM

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

FLAGG · 01-25-2005, 02:56 PM

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 · 01-26-2005, 02:03 AM

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.

01-24-2005, 03:02 AM	#1
kevinr1970 Senior Member Join Date: Aug 2004 Location: Everett, WA Posts: 2,316	A little help please. 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? __________________ 2009 Honda Fit CfC (bsf 44.9 mpg) 2000 Tahoe Limited 1991 GMC CrewCab Dually 2wd, will end up swb, not dually and replace CCswb below 1991 GMC CrewCab Dually 4x4, just going to fix things up for now 1982/1989 K5/GMC Jimmy 2wd 1987 GMC 1/2 ton swb 2wd Crew (sold) Last edited by kevinr1970; 10-04-2007 at 11:28 PM.

01-24-2005, 04:18 AM	#3
kevinr1970 Senior Member Join Date: Aug 2004 Location: Everett, WA Posts: 2,316	For the 700r4, or do I need to hook something up to it to get my TC to lock-up? __________________ 2009 Honda Fit CfC (bsf 44.9 mpg) 2000 Tahoe Limited 1991 GMC CrewCab Dually 2wd, will end up swb, not dually and replace CCswb below 1991 GMC CrewCab Dually 4x4, just going to fix things up for now 1982/1989 K5/GMC Jimmy 2wd 1987 GMC 1/2 ton swb 2wd Crew (sold)

01-24-2005, 08:42 AM	#4
Phuloi68 Senior Member Join Date: Dec 2003 Location: Valparaiso, In Posts: 1,114	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. __________________ Phuloi68 Indy survivor Norwood survivor Big Sandy survivor for those who fight for it... F R E E D O M has a price the protected will never know.

01-24-2005, 12:16 PM	#5
kevinr1970 Senior Member Join Date: Aug 2004 Location: Everett, WA Posts: 2,316	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 __________________ 2009 Honda Fit CfC (bsf 44.9 mpg) 2000 Tahoe Limited 1991 GMC CrewCab Dually 2wd, will end up swb, not dually and replace CCswb below 1991 GMC CrewCab Dually 4x4, just going to fix things up for now 1982/1989 K5/GMC Jimmy 2wd 1987 GMC 1/2 ton swb 2wd Crew (sold)

01-24-2005, 02:34 PM	#6
60-66 Nut Professional Beer Tester Join Date: Aug 2004 Location: Louisiana Posts: 453	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 __________________ 60 Ford F100 Custom Cab 61 Apache Short Fleetside 64 C10 Short Stepside 65 C80 409 V8 5spd(X-Firetruck) 83 GMC 350 Olds Diesel 85 GMC Short Bed 86 GMC Short Bed 90 GMC R3500 Crew Cab 92 GMC 1500

01-24-2005, 03:25 AM	#2
gchemist BAD BOW-Silverado XST Join Date: May 2000 Location: Senior Member from Austin, TX Posts: 6,431	That thingy is the lockup switch for the torque converter.

01-25-2005, 02:56 PM	#7
FLAGG Registered User Join Date: Feb 2004 Location: St. Albert, Alberta, Canada Posts: 89	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.

01-26-2005, 02:03 AM	#8
jimfulco Registered User Join Date: May 2003 Location: Shreveport LA Posts: 3,170	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.



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