heat from defroster only

[TorontoJohn]

Ok, from the minute I bought my car the heat has not worked. I can't change which vent the air comes out of. I can move the selector but it doesn't actually change the vent. Now I am not as much of a noob as I would overlook the obvious. There is no vacume leak in the engine bay.

I have the vacum tree that runs the heat on the passenger side firewall disconnected now but I did hook it all up. I bought all new lines, hooked the the one end to the cannister, the other to the vacume tree, and still the vents wont change.

Under the dash the vacum hoses are all there, and seem to be connected properly. So I am thinking it much be some kind of mechanical failure somewhere.

Any suggestions would be really appreciated. This issue is more of a nusence then anything, as I rarely drive the car in the cold. I am just somewaht of a perfectionist and am going through the car(post carb swap) with a fine toothed comb.

 

[PRO50SC]

If you manually move the dashpots under the dash does it change or for that matter, when you change the control setting on the dash can you see them move on the heater box. If the answer is yes, then most likely there is something wrong in the heater box.

 

[PuterAmI]

I know this is 5.0 Tech, but what year car do you have?

I have the vacum tree that runs the heat on the passenger side firewall disconnected now but I did hook it all up. I bought all new lines, hooked the the one end to the cannister, the other to the vacume tree, and still the vents wont change.

This doesn't make sesne to me. The vacuum is not hooked up? The tree is on the passenger side?

On a Fox, the tree is on the driver's side. A small hard line connects to the tree and runs across the top of the firewall to a three-way check valve at the passenger side. Here, the vavle connects to 1) the vacuum reservoir that resides in the passenger fenders, and 2) a small line that goes in through the foam at the heater box and feeds source vacuum to your controls.

Check for vacuum at your check valve. It is very common for the hard line going across the firewall to have a leak that cannot be seen. If you have it there, check the yellow line inside at your controls. It's common for this to come out.

If that troubleshooting doesn't help, post again.

 

[TorontoJohn]

If you manually move the dashpots under the dash does it change or for that matter, when you change the control setting on the dash can you see them move on the heater box. If the answer is yes, then most likely there is something wrong in the heater box.

Well I will check that today. I am planning on taking out the glove box, and tightening any bolts that need tightening under there. Will let you know. Oh, and the AC has been removed from the car. So I was thinking maybe they forgot to re-connect it all properly after they disconnected it.

 

[TorontoJohn]

I know this is 5.0 Tech, but what year car do you have?


This doesn't make sesne to me. The vacuum is not hooked up? The tree is on the passenger side?

On a Fox, the tree is on the driver's side. A small hard line connects to the tree and runs across the top of the firewall to a three-way check valve at the passenger side. Here, the vavle connects to 1) the vacuum reservoir that resides in the passenger fenders, and 2) a small line that goes in through the foam at the heater box and feeds source vacuum to your controls.

Check for vacuum at your check valve. It is very common for the hard line going across the firewall to have a leak that cannot be seen. If you have it there, check the yellow line inside at your controls. It's common for this to come out.

If that troubleshooting doesn't help, post again.

It is a 87 lx 5.0

Ok, sorry for the confusion. I was calling the three way check valve the passenger side tree. I didn't know what to call it, sry!

There is only one line connected to that check vavle, and that is the line that goes through the dash. The other lines have all been removed. So I bought new hoses and hooked up the tree to the check valve. My vacum cannister (resevoir)broke, so I don't have that in there right now. I just blocked the other side of the check valve but still there was no control of the vents.

Now, the vacum check valve is supposed to mount hard onto the firewall am I right? If so, something is wrong! Mine is hanging about a foot out of the firewall. If it is supposed to be tight in there I would conclude that something isn't connected!

ty

 

[sgarlic]

Yep, there's a line at the vacuum tree labeled A/C, and if it's not connected, or capped off, the unit will only operate in defrost mode.. enjoy that heat once you get it back!

 

[PuterAmI]

Now, the vacum check valve is supposed to mount hard onto the firewall am I right? If so, something is wrong! Mine is hanging about a foot out of the firewall. If it is supposed to be tight in there I would conclude that something isn't connected!

It does not matter how it is mounted. That has nothing to do with whether you are getting vacuum or not. It may mean that your supply line going into the cabin is not connected. Have you done this as I mention above?

Did you test your vacuum with a vacuum guage? Since you do not have a reservoir, there is no need for a three-way check valve. Verify that you have source vacuum from the tree and hook it directly up.

The vacuum source ends up at teh vent controls with the yellow line. Trace and test your vacuum to there and post results.

 

[87_stang]

Check for a vaccum leak on your controls/knob. I have the same problem with my Blazer and I found the leak on the back side of my knobs. Still need to get a replacement for mine. I know how it is, defrost only can really suck!

 

[pa308]

it is definately vaccum line had same issue wit mine when i took dash out.its behind the dash about in the middle towards bottom i believe mine was yellow good luck

 

[tmoss]

Here is a picture.........

 

[TorontoJohn]

sorry for the late response...

I didn't get a chance to look at the car yesterday because I had to pick up my bike from the shop. I planned on inspecting it today but it's monsoon season outhere. So as soon as I diagnose what I believe the problem is I would inquire as to what course to take.