Air Coming thru Defrost Vents

[chrismc101]

While I'm driving, I can feel outside air coming in thru the defrost vents in the front dash & by my feet. It's cold as heck in NC this year and I need to get this fixed.

Can anybody think of what this could possibly be? I have everything off on my defrost/heater/AC swtiches, and the fan is on th eoff position. What could it be? Someone, please help me out.

Thanks in advance.

[HoodStrype]

As far as I've known, all cars after a certain year do that. Something about "fresh air" and "health". I don't know what year that was but my 86 did that as well. If you had that heater core fixed you could set the temp coming thru... but like I said, mine will never get fixed.

[DZEE'S LX]

Make sure your heater core is working. You should be able to get cool or warm air out of the vents by changing the temp knob.

If that is OK get your head behind the dash, or you might have to remove some of the stereo and console plates, and look for the cable that is connected to your temp knob. The cable is connected to a lever that moves the mixing door inside the case. You should be able to move the door from stop to stop while you move the knob from cold to hot. The door is the mechanism that "decides" how much cold or hot air should flow to the vents/heater/defrost vents.

You might also find that the cold air draft goes away if you leave the fan on low and pick a vent or heat setting.

[84LX89GT]

chances are that if there's outside air coming in the fresh air flap door is leaking or damaged. There's a door that is vacuum operated (or cable/linkage depending on what year) that when you set your system on vent or A/C fresh air is allowed in, putting it in max a/c closes the flap to recirculate and further cool/heat the in cabin air.
The things i'd check is the seal around the steering shaft, see if any body plugs are missing (rubber grommets out of place, etc.) and worst case is take out the entire dash and heater plenum and check all the seals and fresh air inlet door.

[chrismc101]

I notice under the hood that someone disconnected the two hoeses that run to the heater coil for the car to run heat. What they did was take piece of tubing and ran the two hoses together. I pulled them apart and I noticed (antifreeze) maybe (I don't know) coming out of the hoses.

WHY would someone have these two hoses ran together in this nature? What purpose does it serve for them to be connected? I know I wanna have my heat running. If I unhook them from each other, which hose goes to which connection?

Somebody help me out, it's about to get cold in NC, even though FOXIE is put away for the winter & beginning restoration/modificaions for summer.

[DZEE'S LX]

Someone has simply bypassed the heater core. I can think of two reasons why this might have been done:

1. Heater core is leaking. You don't mention the year of your car but most fox body Mustangs are a PITA for replacing the core. You have to pull the console, instrument panel, and dash to get to the case that houses the core. This can be a significant and frustrating job, but it is definately doable if you have the patience for it.

2. Mixer door is not working right and someone wanted the air conditioner to run colder by having no warm air mixing when the A/C is on.

3. Someone told the previous owner that bypassing the heater core would produce an extra 50 h.p.

I'd guess reason #1 is the culprit but you can simply hook the hoses back up and see if anything leaks inside on the passenger side or under the car after running the engine at temp for awhile (possibly days). If your windows fog up easily that is also a sign of a bad heater core. You can also smell the antifreeze because the fan will fill the cabin with that lovely scent.

Can't remember which hose goes to which side.

Good luck!

[Ieatcamaros]

They disconnected the hoses because they didn't want to put a new heater core in it. When you hook them up, you will either get a wet floorboard or your windshield will keep fogging up. If you want to restore heat, you will have to put in a new heater core and then hook up those two hoses. The one coming from the intake manifold goes in the left side(driver's side) of the heater core. The other one is the return line and it goes to the water pump. BTW, that is antifreeze in the hoses and it is supposed to be there.

[chrismc101]

Thanks for the info. It's obvious that, that is why even though I haven't checked it. My FOXIE is an 86 5.0 GT. I'm not too much worried about it cause I've decided to part her for the winter & get her ready for the summer where heat isn't needed, lol...

I just wanna get the supposed to be running thing s running. Ya know. I'm going small, not crazy, modifications. Wanna get her at about 300 HP at the rear wheel & I'll be happy.

I already have and cold air intake kit, MAC shorty headers and BBK Offroad H-pipes on her. So, I'm sitting at about 240 HP right now.

To come is a 65mm TB, '93 Cobra upper/lower intake manifold, 3.55 gears, subframe connectors, short shifter, underdrive pullies, & aluminum radiator. A BOMB ass white/black paint job and restore the interior & I'll be a happy camper!

[Ieatcamaros]

You'll be happier with 3.73 gears.

[chrismc101]

Why 3.73s instead of 3.55s? I've heard guys talk before but not in deatil why this gear over that gear.

So help me out or give me a lil clarity on why 3.73s over 3.55s. Thanks any and everybody.

[tmoss]

If your vlower only blows air through to the window and footwells, you have lost vacumm power.........see the diagram. You either lost the vacuum contrtol in the engine compartment or the yellow vacuum hose has pulled off the vacuum motor than changes air from the window/footwell to the dash vents.

[Ieatcamaros]

.........

Wrong thread, sorry.

[Drivingzone]

how do I make a new post on this site?

[j-wigg]

Originally Posted by tmoss

.....or the yellow vacuum hose has pulled off the vacuum motor than changes air from the window/footwell to the dash vents.

WHERE is that vacuum motor located at? Mine is disconnected (connected to the back of the ac control). i'm cannot see anywhere obvious. a general location would be apprieciated.

[j-wigg]

found it behind the instrument cluster clear as day. fixed it. now to get it colder

[DIESEL DOCTOR]

Originally Posted by tmoss

If your vlower only blows air through to the window and footwells, you have lost vacumm power.........see the diagram. You either lost the vacuum contrtol in the engine compartment or the yellow vacuum hose has pulled off the vacuum motor than changes air from the window/footwell to the dash vents.

I applied vacum to the defrost vacum motor and all air still blows through defrost vent.how do you replace vacum motor

[tmoss]

you buy a new or used vacuum motor and replace yours