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k5 tach and hvac wiring

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 1975k5, Feb 28, 2001.

  1. 1975k5

    1975k5 Registered Member

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    I recently purchased a 1975 k5 with factory a/c. I cannot manually select anything but off. When I move the controls, nothing happens. I have pulled the controls out and all the vacuum tubes look in good shape, but there is a orange wire on the back that is disconnected. Does anyone know where this wire is supposed to go? Also, my blazer has a gauge cluster that has a tach where the fuel gauge is on most blazers. Is this tach a factory option or is it aftermarket? It has three wires on the back that are disconnected. They are black, pink, and brown. Any ideas where they go?

    thanks.
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    Well, if the tach loks stock (the numerals are the right color, size, script) then it is likely stock. Also, you will have a little gas gauge where the clock usually is on other trucks, the lower left position.

    Black is ground, Brown goes to the "tach" connection on the distributor, and the pink goes to an ignition hot lead. Not sure if on the '75's if you can plug accessories into the front of the fuse panel or not, like you can the later trucks with plastic fuses, but I just went to the wrecking yard, got wire and the connector on teh end from a truck for the ground, and the same for the ignition lead (such as the plug for power windows at the fuse panel, and soldered the tach leads to them, and plugged it in. The tach lead I believe came off a Camaro (very good source for tach stuff, since most had them, if not all) and should be pretty universal. Come to think of it, a mid 70's camaro tach harness may plug right into your wiring.



    Dorian
    My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
     
  3. Bigd

    Bigd 1/2 ton status

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    The tach is a factory option i had it in my 76.THe black wire goes too a body ground.Brown goes too negative side of coil or tach lead on hei.Purple goes too ign power source.I just had mine apart.There was a orange wire going too the cig lighter.Might want too check if that is it.Is the vacuum pod under the passenger side hood hinge connected or broke.I know if mine is not hook my controls will do nothing.
     

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