heater need heat

[noslow1986]

why is it the heat only comes out of the front dash defroster. and not my vents and floor. is there a switch or lever behind the control panel could be broken. i need to know where the heat box vent is and how to get to it. its an 86 mustang
know i been reading does the a/c vacuum line on the back side of the firewall run the heat too, if so from the a/c line where does the vacuum line go too

 

[oldskolbus]

Nice setup... I have a 86 with most of the same stuff. My third 86. If I remenber right when you move the lever on the vent controls there is a metal line that you can see on the passanger floor near the tranny hump. There is a metal clip that holds the line in. I think this controls the flapper inside dash. the clip might be loose or broken thats why it is stuck. I'm at work now so I can't check. I think the vacuum line goes to the air intake on the passanger floor board. The one I had with ac diden't work.
Hope I could help

 

[BlownFiveLiter]

Chances are, it's the vacuum line that controls the HVAC. Gotta figure, 22 year old plastic lines that have been exposed to the elements and underhood heat are going to end up becoming brittle over time. Check the vacuum lines along the firewall for any cracks, or breaks before you go tearing into the dash, as you'll probably find your issue before you get yourself up to your eyeballs in work, only to find later that it was a simple vacuum line issue. When that line breaks, it defaults to blowing the defrost, so that's why I'm thinking it's the most likely issue.

 

[SuperStang83]

It could also be that one of the lines became disconnected under the steering column. I had the same problem on my car and a buddies car, and we had to get on our backs and finagle the line back on. I'd check that out first, it's only a two minute fix.


Jacob

 

[Lunch Box]

Question and forgive me for temporary hi-jack didn't want to make another heater question...

whats the difference in heater cores sold that say for w/o a/c and w/ a/c

 

[Black1987Stang]

I believe the cores for without a/c are bigger to take up the space of the missing a/c evaporator but not totally sure, whatever your car came with I would get.

The same thing happened to me 2 winters ago when I was at school and to a school bus at my work the other day, brittle plastic vacuum line broke and defaulted to defrosted..I assume for safety reasons. I took a little 1 inch section of tubing from a flow bench at my school and connected the broken section of the plastic line and voila now have had heat since then.

 

[hotcobra03]

Fwiw 1988 has 3 twist knobs and is vacuum controled ventilation system.i c in manual 5 colors .black is vacuum source.white goes to outside air door.yellow which goes to panel defrost door.blue which goes to your floor defrost door.red which also goes to floor defrost door .fords note when vacuum is applied to both floor defrost vacuum lines red and blue a full vacuum condition exist .when applied to blue only a partial vacuum exists. hope that helps

 

[hotcobra03]

Forgot cable goes to temperature blend door