Resolved No air to the vents, only air to the defrost and feet

[Dontknowchit]

I have read all (that I could find) the threads and checked the usual suspects, I swear. Here is the list so far:
vacuum line under the dash from (a/c) to check valve.
-I ran a fresh vac line from the tree to the far side of the car. The check valve is gone so is AC so I connected the vac line directly to the hose going into the firewall. inspected that hose nub and all looked in tact.
-I checked the yellow vac line under the dash that hooks to a canister, it is in tact and securley attched.
-I checked the vac manifold plug (transulcent gummy block connector under the dash.
-I checked the red, blue, white, and black vac hose lines behind the center consule leading to the controls, securley attached.
-I checked the vents are open at the dials

What is next?
just trying to get the vents working, fan still runs strong

FYI: The previous owner removed the A/C lines, the expansion valve, and dryer. The compressor, condenser and evaproator are still in the car but of doubious functionality. Thinking some day I may get a old system and reinstall but right now just trying to get vents working for summer. I typically only drive it in town and with the windows down for summer but not always able.

Thanks, there is not a "surging idle checklist" for this issue from what I have read, its always the vac line. I do not think it is in this case.

 

[85GTStangGuy]

Do the blend/divert door(s) move okay? Make sure they aren't stuck for some reason.

 

[limp]

Do the blend/divert door(s) move okay? Make sure they aren't stuck for some reason.

Not sure if Fox bodies are this way, but I know Ford had a small plastic part that would break on the iinterior heater box that created a problem... They would just wear out.... 50 cent part hundreds of dollars labor to replace if you paid to have it done.....
HOW have you checked all of these lines?? Is there still a round vacuum " box " on the later fox bodies under the pass fender?? If so have you checked this>> Have your dash control valves worn out??

 

[General karthief]

Start at the vacuum tree on the firewall, one is marked AC. Is there vacuum there, fallow the line across the firewall to the rt fender where you'll find a check valve, got vacuum there?

 

[Dontknowchit]

Start at the vacuum tree on the firewall, one is marked AC. Is there vacuum there, fallow the line across the firewall to the rt fender where you'll find a check valve, got vacuum there?

yes that is a new line I installed. The check valve is gone. I ran anew line from the tree to the passanger side to the A/C pipe inlets. There is a vac line there that I connected to that goes thru the firewall.

 

[Dontknowchit]

Do the blend/divert door(s) move okay? Make sure they aren't stuck for some reason.

Yup they look good, I poked them with a stick and they flap

 

[Dontknowchit]

I think I may have found the issue but its not looking great. I started the car and left the fan running and noticed that over buy the firewall opening where the AC condenser connnection pipes are and that little vac line goes thru the firewall it felt like air was blowing out of it. That seemed odd. I gingerly wiggled the vac line going into the firewall and it appears it may no longer be attached to wherever it goes into the air box. Does anyone have a picture of the back of the air box where this line goes in for me to determine if this is fixable without removing the dash?

 

[General karthief]

I need that info too, had my dash out years ago and don't remember where it went inside and mine needs new line.

 

[Dontknowchit]

After stalking some youtube videos we may be able to run a coat hanger into the firewall on top of the air box and just make a new connection to the manifold block from what I am seeing in these stills form a video. cannot yet confirm. this makes sense to have the vacum signal to t offr after in came in to distribute to the needed systems.

I think it's this one:

 

[85GTStangGuy]

yes that is a new line I installed. The check valve is gone. I ran anew line from the tree to the passanger side to the A/C pipe inlets. There is a vac line there that I connected to that goes thru the firewall.

I think that the check valve, tee and vacuum reservoir line are needed for proper operation of the hvac system.... particularly when their is little to no engine vacuum. Not sure if the revisions that have been made to the A/C affects any of this though.

 

[Dontknowchit]

I got it fixed! Turns out that I checked all the vac lines under dash before I reconnected the new vac line under hood. When I attached under the dash I pulled the black feed out of the manifold block. There is a "holder" on the air box so you can tug on the line and feel tension or slack that is not indictitive of the full line path. I added some leinght to the interior line once found and I have vents! Thanks for all the help and hopefully the sluething I did helps someone else. uktimatley, I think the air box blocks the "coat hanger" attempt but if you had the patience to jiggle it, that could have worked.

 

[LFierro-Vega]

I am having this same problem. I looked under the glovebox and found the rubber vacuum connector where four hoses meet and one was unplugged. I reconnected it, but the problem persisted. I am worried that I pulled on the black hose too hard and it disconnected from somewhere under the dash. Is this possible or does the hose run directly to the vacuum tree. Where is the check valve and do I need to take the dash off to check if it is connected. What can I do?

 

[Noobz347]

I am having this same problem. I looked under the glovebox and found the rubber vacuum connector where four hoses meet and one was unplugged. I reconnected it, but the problem persisted. I am worried that I pulled on the black hose too hard and it disconnected from somewhere under the dash. Is this possible or does the hose run directly to the vacuum tree. Where is the check valve and do I need to take the dash off to check if it is connected. What can I do?

Go down the parts store and pickup a few feet of vacuum line. Comb through and replace every line that looks the least bit worn.

You will probably find some other breaks and leaks while you are at it.

You can go through the lines ahead of time and take sample sizes with you to the parts store.

Pickup some dielectric grease while you're there too. It comes in handy for vac lines and electronic connectors.

 

[LFierro-Vega]

Go down the parts store and pickup a few feet of vacuum line. Comb through and replace every line that looks the least bit worn.

You will probably find some other breaks and leaks while you are at it.

You can go through the lines ahead of time and take sample sizes with you to the parts store.

Pickup some dielectric grease while you're there too. It comes in handy for vac lines and electronic connectors.

What’s the grease for?

 

[Noobz347]

What you would imagine... Tight fits.

 

[Dontknowchit]

I am having this same problem. I looked under the glovebox and found the rubber vacuum connector where four hoses meet and one was unplugged. I reconnected it, but the problem persisted. I am worried that I pulled on the black hose too hard and it disconnected from somewhere under the dash. Is this possible or does the hose run directly to the vacuum tree. Where is the check valve and do I need to take the dash off to check if it is connected. What can I do?

My troubleshooting was, 1st check vac line in engine bay @ firewall if hooked up or broken. Then look under the dash for where the black hose exits (have to get upside down on passanger side and feel around behind the blower box. trace the balck line as far as you can up to see if still connected. Grab a friend and get have them blow through the line at the firewall, see if you can feel the air at the interior black line. If flow feels strong, you are still connected and you may have issue at vac block connector pictured or inside your air box itself with the diverter flap. if flow is weak or not there you may have broken the line behind the fan and its just hung up. In that case pull the passanger seat, then pull the fan blower box to repair/replace the line. Pulling the fan box is a pain due to positioning but really just a few screws. It's modular to the rest of the air box so it can be removed.

Really, worst case senario is the diverter valve/flap inside the air box is stuck or broken, if so, everything comes out. May be able to somehow rattle it loose or something, but that would be happy accident if that worked. find the diagram of the inside of the air box and that will make sense.

Check your vac line first as that is the most likley issue.
Second most likley would be your connections at the block under the dash are bad or wrong or too much leakage from other uncapped ports on the block.