Vent Vacuum Controls.. HELP PLEASE!!

Discussion in 'Fox 5.0 Mustang Tech' started by Mavrick, Dec 28, 2003.

  1. The vents in my stang will not respond, when i want to change them from blowing on the floor, or the vents, etc. It is stuck in the defrost (default) position, and i can't figure out whats wrong.

    How many vac cans are under the dash that could be messing me up? I have check the one behind the glove box, its fine, the one on the drivers side behind the gauge cluster, i hooked it up (yellow vac line) and it still does this.

    The line going accross the back of the engine bay, i found was not connected. I hooked it up, and it doesn't appear to be cracked or anything.

    Could anybody point me in the right direction?

    Thanks in advance.. I am pretty damn frusturated with this crap.
  2. If you dont have a hand vacuum pump to test with (they are nice), pull the line in the engine compartment where it goes through the firewall and suck on it. Block it with you tongue after forming a suction. It should hold the tip of your tongue if you formed a good suction. If not there is a leak. Best way to find it is by the hissing sound it will make. Run the engine in a quiet spot, then shut it off and listen. I have been able to locate leaks by running the engine and listening under the dash. You can test individual diaphrams like this too. suck and hold. doesnt sound right, does it?
  3. Jerry, i don't know about you anymore buddy :p

    I have that hissing sound.. after i shut my car off, every time it makes a big hiss. That is a vacuum leak?? I'm pretty sure it's coming from under the hood on the passenger side, hopefully it's not the vac stuff under the fender!!

    How can i shut my car off from under the hood so i can hear better?
  4. Should be able to hear it with the car running too. Listen carefully.

    You could try pulling the coil wire, but you may get the snot knocked out of you and I dont know if thats a good idea, with all the electronic stuff around. Prolly something you better let me try first, I makes a good guinee pig. :nice: I still check for spark on a lawn mower by holding the wire and pulling the cord.
  5. I am not sure what year you have, I have a 79 and an 82. But on all of them I think you can access all the vacuum lines by pulling the controls out of the dash, which exposes the switch and the connectors. Then you can check for vacuum from the engine and also test each small vacuum line to each motor and find which one is leaking. You can use a hand vacuum pump or just the old mouth to mouth technique. Or run a long vacuum hose from the engine compartment with a tip on it that will plug into the small hoses, and just try it. You can look in a manual and see where and how many motors there are. It think there are 4, but this is totally from memory.

    Most likely one has pulled off of the vacuum motor fitting or from the connector at the controls. With the engine running you should be able to hear it, in spite of engine noise.
  6. I wish i could run the car, but it's in a tight garage right now... i might buy some exhaust hoses though.

    I tried the mouth-tongue trick with the black line, going into the car (from the engine bay)... it does seem to hold vacuum.
  7. if all you have is defrost then check the vacuum hose going into the firewall by the A/C accumulator. when that hose breaks, you lose vacuum to the controls and it defaults to defrost.
  8. Ok, just doubel checked it with the sucking method.. the hose going into the firewall does not hold strong vacuum. I'll check that tonight and see what i can find.