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No economy controls after motor

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by MNorby, May 10, 2002.

  1. MNorby

    MNorby 3/4 ton status Premium Member GMOTM Winner

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    After I put the new motor in now when I select vent, heater, AC, defrost, etc you don't hear the sucking noise and the heat is directed in one way or another such as defrost or vent. There is a vacuum switch on the firewall on the left side by the AC stuff and that is hooked to manifold vacuum. There is a bigger 4 prong wire connecter hanging in that hole too but I don't see where it goes. This all ahppened after puttin in the '76 400 into my '86 GMC. One plug on the pass side bottom of block on the old motor had some wire going to it and this new motor just had a plug in that hole. That wire went to teh firewall where that vacuum switch and other mystery wire goes in. Any ideas? Thanks
     
  2. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    Correct If I'm wrong, but you don't have the little round ball on the pass side for a vac resovoir do you? I think they dropped that in '84 or '85 because they put a big on the driver's side for the cruise and just used that. Anyways...don't worry about all those electrical wires, those were for the ESC (electronic spark control) stuff. That wire to the block was for the knock sensor. You wanna have some kinda system rigged up with tee connectors and the like that lets your heater controls and cruise use that big resovoir for its vacuum.
     
  3. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Under the hood by the blower motor is a Vacume hose coming through the fire wall. That's the feed line to the controls. It usualy connects to a T on the intake manifold behind the carb. My bet is you left it off and it's hanging loose somewhere.
     
  4. MNorby

    MNorby 3/4 ton status Premium Member GMOTM Winner

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    thanks, I'll check it out. Gotta take the truck to the shop because the tranny isn't locking up. I'll check after I get it back. Thanks for the pointers
     

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