thesameguy

Anyone have any thoughts on an '84 T/A that is roasting me alive? With the vent selector on VENT, heat is coming out of the vents even with the temp set to COLD. I just replaced the little vacuum dial thing and was sure that was going to fix it (mine was physically broken) but I still have seriously warm air coming out.

Is it possible the heater door isn't closing all the way? I removed the cable from the door and tested to be sure it was getting all the way closed, but even still, hot air! It does get a LOT hotter when I put the temp slider to HOT, so I know the slider is doing it's job.

Do the doors wear out? Is this why GM added the heater control valve to later cars? This sucks!

Aaron R.

Without knowing the history of the car, anything is possible.

The heater vent door has a very good, soft rubber that seals off the heater core. I just inspected the one on my 85 last month and it was still in excellent condition. The cable is the first suspect, but if you have checked that and are certain it is closing it sounds like something else.
This may seem like a dumb question, but are you sure the temps you feel aren't normal? If you aren't running your a/c and it is hot outside the vent temps will be pretty warm.
My vent ducts are sealed up better than factory and all working correctly and I get vary warm air without the a/c on.

thesameguy

I don't have much history on the car - I got from a girl who got it from a guy who got it from another guy, and none of them knew what was going on. I've been slowly going through it fixing it up - I paid $400 for it, and that price reflects its condition.

Last night I removed the cable from the heater box door lever and held it in the closed position, heat was still coming from the vents. I reattached the cable, and it looks like the cable does move it into "full closed."

It gets a LOT hotter when you turn the heat up, but the air coming out is definitely a lot warmer than ambient air temperature.

Any idea how difficult it is to remove that door to check out the seal? Based on the condition of the rest of the interior of the car, I wouldn't be surprised to find it wrecked, too. If it's too difficult, I'll put it off for now - I've got bigger fish to fry, and with the new vacuum valve at least OFF does in fact turn it OFF.

This really started out just trying to fix vacuum leaks - that's done, and the car is running & driving pretty well. I redid all the steering components, motor mounts, transmission mount, front swaybar, and every vacuum hose & emissions component. It's not shifting right yet, but I put in a new TV cable and I'm hoping with a little exercise it will stop shifting late - it's better already, so high hopes. Also looks like the steering box is leaking pretty severely, so I gotta deal with that... Once those are done, I'll feel pretty good about it mechanically - I replaced every single brake component about a year ago (calipers, MC, rotors, pads). If I can get it looking half as well as it drives right now, I'll be satisfied.

88gta_hiflyer

iTrader: (1)

One option would be to bypass the heater core at least temporarily. That way you can at least focus on more important things and be able to drive the car comfortably (relatively speaking).

thesameguy

Yeah, that is definitely an option. I thought about even putting a valve in there, so once winter rolls around I can just flip the valve on and *still* not worry about it.

Bman1320

So, I have an '86 Z28 and have the same relative problem.. The differences are that #1: my cable IS broke, and #2 it still puts air to the floor and the vents. But the vacuum switch is working because my stuff turns off when the switch is off.. I'm not quite sure about how to get under the dash, mainly because I've only owned this car since november.. So if anyone could help me out that would be awesome.

thesameguy

The cable controls how far open the heater door is; the vent control is done with vacuum. If you're cable is broken you're not going to be able to control the temperature at all. Basically, you can have full vent control and no temperature control, which is what it sounds like you've got. I'd replace that cable - it's extremely easy.

Maverick H1L

iTrader: (8)

Well, I have a bigger problem with my heater case in that the lever controlling the heat door is broken (at the door shaft, not the control head), meaning the only way I can shut the heat off is to shut the coolant flow to the core off with the vacuum valve. If your car doesn't have A/C, it may not have this. If it does, the valve may not work. Pull a vacuum on it if you have a pump to see if it holds vacuum AND if it blocks coolant flow when vac is applied.

mjshort

I have the exact same problem with my 82. I looked at the door that's supposed to close off the heat and it looks good (not worn or broken). It looks to me like it's just a poor design. Why did I notice it when it was new? I suspect it was because the A/C was on then (it doesn't work now). I was thinking of same fix of putting a valve in the heater line. But I'd like to know if there really is a problem, or it's just a poor design as I suspect.

mjshort

I just found this in another thread which may be our problem:

I'd still check those vacuum lines, and check the vacuum line on the heater diverter valve as well. The heater diverter valve is under the hood - looks kinda like a UFO on top, and has 2-3 heater hoses running in and out of it. What it does is when you switch the controls to heat, the heater controls opens a vacuum line that runs to the diverter - this vacuum opens a valve in the diverter that allows the hot water from the radiator to circulate through the heater core. When the valve is closed (ie controls set on cool side), the valve keeps the hot water from running through the heater core, thus reducing the amount of heat in the cabin.

Alot of us remove the heater diverter valve to clean up the engine bay - but we then have hot water circulating through the heater core all the time. To keep it or not is preference - but if it's there, make sure that vacuum line is not torn or loose or anything. AND - check all the other vacuum lines as well, in an effort to ensure that's not any issue causing your engine rough running problem.

I hear a hissing noise when I turn the air conditioning / heater switch. Plus I get heat in the cabin. Sounds like it could be causing the problems.
Here is the thread:
https://www.thirdgen.org/forums/inte...trol-help.html

Maverick H1L

iTrader: (8)

FYI, there's 2 vacuum switches on the control head. There's the one for the diverter doors and a separate one for the heater control valve (which is what it's called at parts stores). The one for the HCV is attached to the temp control slider at the bottom, and will have 2 hoses on it, both black. Check the switch and the lines to make sure they're not broken.

mjshort

I just found this in another thread which may be our problem:

I'd still check those vacuum lines, and check the vacuum line on the heater diverter valve as well. The heater diverter valve is under the hood - looks kinda like a UFO on top, and has 2-3 heater hoses running in and out of it. What it does is when you switch the controls to heat, the heater controls opens a vacuum line that runs to the diverter - this vacuum opens a valve in the diverter that allows the hot water from the radiator to circulate through the heater core. When the valve is closed (ie controls set on cool side), the valve keeps the hot water from running through the heater core, thus reducing the amount of heat in the cabin.

Alot of us remove the heater diverter valve to clean up the engine bay - but we then have hot water circulating through the heater core all the time. To keep it or not is preference - but if it's there, make sure that vacuum line is not torn or loose or anything. AND - check all the other vacuum lines as well, in an effort to ensure that's not any issue causing your engine rough running problem.

I hear a hissing noise when I turn the air conditioning / heater switch. Plus I get heat in the cabin. Sounds like it could be causing the problems.
Here is the thread:
https://www.thirdgen.org/forums/inte...trol-help.html

thesameguy

I haven't even been able to determine how to inspect the door - is it painfully obvious & I'm just dumb, or is disassembly required? Just based on other, similar designs, I'm betting that the insulation around the door becomes flattened over time and doesn't block off the core as well as it should.

thesameguy

I'm not sure where I read it, but my understanding was the heater control valve wasn't added until like '86 or '87, possibly to fix this exact problem we're having on our early cars. Rockauto.com lists the UFO-shaped heater control valve for an '87 Trans Am but not my '84, for whatever that's worth.

mjshort

Yeah, I went and looked on my car after reading the post and there is no such device. I guess the hand turn valve might be the answer. Does anyone know if the diiverter valve can be easily made to fit pre '86 camaros?

Bman1320

So, along with my cable being broken, it's stuck too. any common places that stick?

thesameguy

I'd bet it could, but you'd need to get a later-style control panel to run it, too. It's just a vacuum operated valve, but you'd need something to generate that vacuum, something the later-style panel does automatically.

thesameguy

Why not just remove the whole cable and replace it? It's only a couple feet long, not difficult.