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Have a few vent questions...

Discussion in 'The Garage' started by grafixxman, Oct 2, 2005.

  1. grafixxman

    grafixxman Registered Member

    Dec 1, 2004
    Likes Received:
    My 87 has a/c that will freeze your boys off... :D I have noticed here lately that when I turn everything to off on the controls ( truck running ), that I get a "ssssssss" noise like when you turn the truck off w/ the a/c on. It continues from idle to whatever rpm...till I can't hear it anymore over the motor. I have tried playing with the heater box and the "rods" on it to see if it was some sort of vaccuum issue and not completely pulling the doors shut. I have had no luck. I don't know what to do from here. It sounds almost as if there is a vaccuum leak...but there isn't. Any thoughts?

    Secondly, as I said earlier, my a/c works great. The only drawback is it doesn't blow really hard from the vents. It blows harder than hell from the floor ( even when the vents, not floor option are on ( if the a/c is on or the heat ). I realize that is almost a 20 year old truck, but I figured with the sound of the blower motor kicking a$$ ( working to its full potential ), it should blow harder out of the vents. I have tried everything I can to re-align the ductwork and seemed to do a pretty good job. I don't expect it to be like a brand new vehicle ( ie: blowing my hair like a tornado ), but I figured it should be a little better than it currently is.

    Notice how I said it still blows from the floor vent even when the dash vent option is selected? Is that right? It blows like a m-fr from the floor. I have tried holding my hand over the floor vent and the other free hand up to the vents to see if there was much change...there isn't...not extremely noticeable anyways.

    Am I dealing with some sort of heater box vaccuum issue? Has anyone encountered this before...and decided to do something about it? The vent "problem" isn't as much of a concern as the hissing noise I hear when I turn all the controls to off. That tells me that something in there ain't jiving. Can anyone help please?


  2. jhellwig

    jhellwig 1/2 ton status

    May 7, 2005
    Likes Received:
    Bonaparte, Ia
    Sounds like a vacume problem to me. The actuator to direct the air is probaly shot.
  3. Can Can

    Can Can Pusher Man Staff Member Super Moderator

    Feb 17, 2000
    Likes Received:
    Cochrane, Alberta, Canada
    All the vent/floor/defrost controls are vacuum-operated on AC-equipped trucks. It sounds to me like you have a loose vacuum connection somewhere behind the dash, which would explain both the hissing sound and the lack of vent selection.

    You'll have to start by taking off some of the black air tubing and tracing vac lines. It's been awhile since I tackled the job myself, but IIRC there's 2 vac pods that control where the air goes- One is below the glovebox(switches from floor to vent) and one if below the ashtray(switches from floor to defrost).

    The problem could also be where the linie goes from the engine bay through the firewall. Like I said, start tracing vac lines backwards and I'll bet you'll find the problem.

    Good luck, and keep us posted, brother!!

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