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clicking sound from little box on firewall

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by TheBlazerKid, May 2, 2000.

  1. TheBlazerKid

    TheBlazerKid 1/2 ton status

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    i have a 71 K5 blazer 4x4 with a 4-speed manual tranny and whenever the key is ON or at ACC when i wiggle the shifter theres a little clicking noise. i investigated this farther and foudn the source,little grey box with a bunch of wires coming out,dont know what it is for,too my knowledge the only wire coming out of the tranny would be for the backup lights,.....anyoen know what the deal is with the clickety clack.
     
  2. 6.2 man

    6.2 man 1/2 ton status Premium Member

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    Sounds like aftermarket maybe some kind of ignition box . Backup lights are on the transmision .
     
  3. Corey-88K5

    Corey-88K5 1/2 ton status

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    I would bet that something is shorting out in the collum. That box sounds like a relay of some sort, and its catching the short instead of burning your truck up. Got an extinguisher?

    Corey
    88K5

    [​IMG]<font color=red>Girls Like Guys In Bow Ties
    http://www.geocities.com/corey_perez
     
  4. Blazer79

    Blazer79 1/2 ton status

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    What size is the box? and where exactly is it?

    <font color=black>//////
    What the heck!...Drive it like gas is $0.50/gal!!!
    </font color=black>[​IMG]
     
  5. Blazer1970

    Blazer1970 1/2 ton status

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    That box on the firewall is the relay for the TCS (transmission controlled spark) system. There is a second switch (besides the back up light switch) on the tranny that indicates when it is in 4th gear. The TCS system controls when vacuum advance is used. The system consists of; the switch on the tranny, the relay on the firewall, a temperature switch (usually in the pass. side head), and a vacuum solenoid valve that is in line with the vacuum line from the carb to the distributor. the solenoid valve is mounted on top of the intake beside the carburetor. If the solenoid valve is already gone or bypassed, you can eliminate the rest of the system too. This system blocks the vacuum advance under certain conditions. I have rarely seen a Blazer (or truck) that still has this system connected. I eliminated it on my '70 Blazer when I rebuilt the drivetrain, but the solenoid valve was already bypassed anyway. I used the switched hot wire from the relay for my electric choke. I am not sure exactly what benefit this system was supposed to give. I think it was for driveability, and not emmissions.

    Tim

    1970 Blazer CST 4X4 350 SM465 NP205
    1987 Suburban 4X4 350
    1988 Chevy Pickup 4X4 350
     
  6. TheBlazerKid

    TheBlazerKid 1/2 ton status

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    AAH HAA!!! thank you very much for your input on helping me figure out what it was, I thought there may be something shorting out but now it all makes sence,I'll just eliminate it most likely,

    Thanks again,

    The Blazer Kid
     

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