AC/Heater Controls and Air Flow Problem [Archive] - El Camino Central Forum : Chevrolet El Camino Forums

: AC/Heater Controls and Air Flow Problem


84-Elky
10-01-2010, 09:47 AM
Need some problem solving help in understanding what is going on with ’84 El Camino. Have read many threads here but none seem to describe my problem. All control panel settings direct air where it should go, but with one problem – there is always air coming out of the heater vents, even with everything turned off (both levers are fully to the left). Some detail below but necessary:
- Car does not have vacuum controlled heater control valve.
- No vacuum leaks
- The heater vent air volume is car speed dependent; with more air blowing the faster the car is going.
- With everything off, the air is hot as if the heater is on.
- The AC/Heater door is, I believe, fully closed to block heat. That is, the threaded rod attached to the AC/Heater door is pushed in toward the firewall as far as it will go (I’ve pulled the rod out of the holder clamp and have confirmed this, but have no way of visually confirming the door is actually moving although it appears to be).
- When AC is on (set to Max, Normal, BiLevel or Defrost), the air from the heater vents is cold.
- The re-circulate door is closed on Max and open on all other settings.

Any ideas on what I can check or do to stop the heater vent air flow? Need to fix this because it really gets hot in the car when AC is off.

darbysan
10-01-2010, 01:39 PM
Without the Vacumn Control on the heater lines, you have hot water circulating through the heater core all the time. You need that control to stop the flow unless you want heat. I think that will fix your issue.

JJLT1
10-01-2010, 02:05 PM
welcome 84
yep,,,you need to stop the hot water flow,,,not the air flow,the blower runs on low all the time...
you could pinch off the hose and try it,,,or get a little manual valve,,,or the original type valve...:texas:

fixittroy
10-01-2010, 02:28 PM
I had this problem when I got my 84. I had to replace the valve that controld the heater flow.

21yearowner
10-01-2010, 07:38 PM
I had a similar problem and it turned out to be a low refrigerant (sp). Once the AC was fully charged, the problem disappeared.

84-Elky
10-01-2010, 09:06 PM
Thanks everyone for the prompt replies. Yes, the car does not have a heater control valve, but I’ve had other similar era cars that purposefully did not have them and there was no interior heat and no un-requested, high volume air flow. I agree that hot water will always run through the heater core this way, but I was told by someone with a chassis manual that even with the valve installed and working, it is only closed when AC is on ‘Max’. Otherwise it’s always open. And that if the Temperature Door is closed to prevent heat (bottom lever all the way to the left = rod attached to door pushed all the way toward the firewall, which it is), no heated air can enter the car. That makes sense.

But it's really not important. The real issue is: Why is air entering the car from the outside and coming though the heater vents when everything is off? And why the higher the speed, the more air flow?

There has to be an air door somewhere or something that is not closed that should be. And yes, the blower runs on low all the time, but this air flow is speed dependent and not from the blower. Still searching for a solution.

JJLT1
10-02-2010, 05:08 AM
iirc,, its called flow thru ventalation..
that re-circulate door lets outside air in from the pass side cowl area, at the base of the windshield,
and it may be open all the time??,except for max a/c..
.
and yes,i think the flow does go up with the speed of the cruck,,
probly just the change in air pressure around the cruck..
.
here in tex if i have a reason to get into the system,i try to lock that door closed,,
dont need the heat..it seems the vent setting is useless when its above 80*.
.
what may be happning at speed, the hood could be lifting off the rear seal,and letting heat from
the engine compartment get to the cowl vent ?? does that make sence ??
.
i was thinking the 5th gen did have the heater control valve,,i dont have heater hoses on mine
yet,,but i think i remember seeing the vacuum hose hanging there for it ??
good luck..:texas:let us know

Rally169
10-02-2010, 08:34 AM
The heat/a/c blend door should shut off flow to the floor when closed as you show. The foam rubber seal could be bad. You have to take the top of the unit under the hood of to fix. Very hard to get off without breaking.

The heater should have a vacuum controled shutoff valve installed. You can get a plastic replacement from most parts stores . You should find two 1/8" plastic vacuum lines coming from the a/c-heater switch. One violet line goes to vacuum source and one white line goes to the heater shutoff valve.

The blower motor should not be on low all the time . With the switch at off it should not run. It should follow the speed selected. The fan switch could be bad or the fan resistor could be bad. If it doesn't run at high the switch or the fan relay could be bad.

The cowl air inlet shoud close on max a/c like you show.

dougs85
10-02-2010, 09:41 PM
I've had an 85 and now an 87. The AC blower will always run at a low speed when the ignition is on. This is a venting feature built in the car. You are getting heat because of no heater control valve to cut the hot water off to the heater core. Install a heater control valve and your problem will be solved.

Doug

Brian Boru
10-04-2010, 05:01 PM
If there is no heater control valve visible and no vacuum colector(softball) could stopping the flow to the heater core with a shut off valve stop all the heat from entering the cabin. Would this create any other problems. If its cold,open the shut off valve and heat would flow. I have exactly the same problem and wonder if this would work in a mild climate like I live in. Really dont need heat or AC.I'm thinking of doing this until I can locate a local 87 owner and look at his set up.My shop manual helps to some extent but it presumes the unit has all the components referenced. Any help(as usual) would be greatly appreciated. Maybe Ernie , all the way from Europe(allowing for the time zone difference)has a thought. All jokes aside. Welcome home, Ernie. Brian Boru

darbysan
10-04-2010, 08:40 PM
A shutoff valve will work fine. You can also just disconnect both hoses at the heater core and tie them together, or run a loop from the intake to the water pump. I think you could also just cap off the outlets at the intake and the water pump, since their only function is to allow water to flow to the heater core.

JJLT1
10-04-2010, 08:50 PM
http://partimages.genpt.com/thumbs/395115.jpg (http://www.elcaminocentral.com/Detail.aspx?A=BK_6601200_0265434970&An=599001+101987+50014+2014016)this is what napa shows for a 87..and a 84...for a v8...v6 is differant
http://partimages.genpt.com/thumbs/395144.jpg (http://www.elcaminocentral.com/Detail.aspx?R=BK_6601413_0069254521)i have used these manual valves on other cars that dont use a htr control vlv..

http://partimages.genpt.com/thumbs/395119.jpg (http://www.elcaminocentral.com/Detail.aspx?A=BK_6601225_0166870976&An=599001+101984+50014+2014016)this one closes and bypasses...:texas:

BillyJack
10-05-2010, 09:14 AM
Pinch the inlet heater hose closed with a pair of vise-grips and take it for a ride. If your heat issue stops, you need a valve. If not, it's time to look elsewhere.

Bill

Brian Boru
10-05-2010, 11:19 AM
Going to pinch the hose with vise grips as advised.Sounds like the easiest quick fix(test). If heat disappears I'll install some type of diverter until I get a good read of a functioning system. The previous owner tore out AC and must have messed with heater control valve and vacuum collector. Thanks for the help. Brian Boru

84-Elky
10-08-2010, 02:40 PM
iirc,, its called flow thru ventalation..
that re-circulate door lets outside air in from the pass side cowl area, at the base of the windshield,
and it may be open all the time??,except for max a/c..
.
and yes,i think the flow does go up with the speed of the cruck,,
probly just the change in air pressure around the cruck..
.
here in tex if i have a reason to get into the system,i try to lock that door closed,,
dont need the heat..it seems the vent setting is useless when its above 80*.
.
what may be happning at speed, the hood could be lifting off the rear seal,and letting heat from
the engine compartment get to the cowl vent ?? does that make sence ??
.
i was thinking the 5th gen did have the heater control valve,,i dont have heater hoses on mine
yet,,but i think i remember seeing the vacuum hose hanging there for it ??
good luck..:texas:let us know
JJLT1 – You hit the nail on the head with heat from the rear of the hood and air pressure. Thanks. I’m learning more about this AC/Heater stuff than I ever wanted to know. All comments and the attached diagram from a 1986 G-Body Shop Manual have helped my understanding. And by the way, don’t want to start a war but this diagram just further proves why it is not necessary to have a heater control valve. Yea, the Heater Core is always hot, but if air is not allowed to flow through the Heater Core, no hot air can be generated (see “Temperature door” controlled by the temperature lever cable as shown in the “Cold” position).

So here’s what I’ve learned. The hot air from the heater ducts is only felt when the windows are open. What’s apparently happening is that my hood is not totally sealed at the back as JJLT1 suggested and engine heat is escaping there and being “sucked” into the Cabin Air Intake (under the windshield on the passenger side).

When the windows are open, air is not being prevented from entering the cabin as it is when the windows are closed (higher pressure in the cabin with windows closed). So, you get increased air flow into the cabin with windows open, and this increased air flow sucks more air out of the back of the hood which is causing the heat.

When the windows are closed, only a small amount of outside air comes through the heater vents, and its volume is not speed dependent. It never changes, and the air temp is the same as outside. Here, because there is a small velocity of air being allowed into the cabin, hot air is not being “sucked” out of the back of the hood into the Cabin Air Intake.

If my hood was totally sealed at the back, I’m confident that the hot air with the windows open would disappear and be the same temp as the outside air. I’ll stuff a towel along the back of the hood to prove that theory when I get some time.

And a question - How do you permanetly close the Air Inlet Door. Remove the vacuum line from the diaphram, plug the line and then what ??? Thanks.

http://i1226.photobucket.com/albums/ee411/84Elky/G-BodyCabinAirFlow.jpg

JJLT1
10-08-2010, 07:40 PM
check and see if your rubber seal at the back of the hood is still there,,after 25 years??
cant remember if its attached the hood or the cowl on a gbody??
these type of hood hinges dont lift as bad,, like the double scissor hinges did,,
or you may just need to adjust the back of the hood down a little...
.
also the foam seal on the temperature door Rally169 talked about is a common problem i hear,,
which makes me want a heater control valve anyway,,even if its manual...
.
And a question - How do you permanetly close the Air Inlet Door
you may be able to reach it thru the blower motor hole,,thats where i was going to look first...
i havent had a reason to tear in to the elky yet,,but on my truck
as a temporary fix about 15 yrs ago
i stuffed a piece of water proof foam up in the outside hole (seems to work)...
u need to check where the drain holes are tho...
fyi,,with blower motor out,,clean out that side of the evaporator while your there...
good luck and let us know,,,your the a/c duct ex-pert now,,...:texas:

84-Elky
10-09-2010, 08:50 PM
I believe the Air Inlet Door and its open/close diaphragm are visible behind the glove box on my car. I say that because I can see that door move only when AC Max is selected. So, if I disconnected the vacuum line to that diaphragm, plug it, then tape the door shut; that should do it, right? Or maybe I should disconnect the arm going to the door if it is accessible and that would accomplish the same thing.

About the back of the hood, I think I’ll leave it as is. My rear seal is new but it does not quite mate with my 2" Cowl Goodmark hood - not exactly made to GM specs. My ride generates a lot of under hood heat with headers and letting that heat out anyway possible is best for me.

JJLT1 - Any chance you could provide the link to the bottom Heater Valve (the redirecting one), or where it might be purchased. Somehow I’m not being linked when I click on it. Thanks.

JJLT1
10-10-2010, 10:28 AM
yep, i think thats the one,,up high,on the pass. side...
most of those vacuum diaphrams are spring loaded,,so yes disconecting the vac. line could do it,,
or connect it to a constant vac. source may be needed,,it depends on if its normally open or closed...
.
with the humidity around here i wouldnt use tape,,it'll probly end up, wadded up in the blower???
.
i have disconnected the arm,,and tie wired it in the position needed,,on an newer electric motor system...

yea,,that site dosnt link very well,,it dosnt save the searches...
go to http://www.napaonline.com/ in the center of the page hit shop online,,,hit no specific vehicle,,
and search for,, heater valve ,,look on the the 4th page,,,there is a lot more choices,,have fun..:texas: