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speedo problems please look

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by doctor4x4, Feb 11, 2004.

  1. doctor4x4

    doctor4x4 1/2 ton status

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    Here's the stats
    1989 fullsize K5
    Upgrade 700r4- 205
    thats the problem
    was a electric speedo
    now is manuel
    bought the special speedo converter but must have switched the 2 wires and blew a inline fuse as all the ones in the fuse block are ok
    or ??
    oh yea when i first hooked it up the speedo pegged at 85
    so i turned it off and back on 3 times the needle tried to surge but the limit peg wouldnt let it go forward so i took the cover off and pushed it back to zero with the ignition off
    now it wont move at all
    anyways spedo dont work any body got a wiring diagram or know how they work when they went electronic ??
    should i be getting a positive voltage to either wire ??
    I hooked up a drill so i know its spinning

    Thanks
    R
     
  2. doctor4x4

    doctor4x4 1/2 ton status

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    top still need help
     
  3. 4xcrazy

    4xcrazy 3/4 ton status

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    Can't help much, but thats interesting you have electronic speedo, i have an '89 Burb and to my knowledge it's cable driven, guess i'll have to double check on it.

    Good luck with that. sorry not any help.
     
  4. Thunder

    Thunder 3/4 ton status

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    Hate to say it but if you hooked it up wrong and pegged the needle then you had to force the needle back. Its prolly time for a new speedo. Either that or your adapter is toast.
    Maby you can return it and try a new one.
    Strange. I have never seen a electric spedo in a 89 either.
    The spedo in my 89 K5, and all others I have seen is/are cable driven. Didn't think they went electric till 90.
    What are you using for a VSS?
     
  5. doctor4x4

    doctor4x4 1/2 ton status

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    yep i was wondering if i broke my speedo
    and mabe it was one of those late made(last on the assembly line so it got 1990 parts k5
    but it was a 700R4 to a np241
    does the computer need info from the speedo to do its job right ??
    I'l post up for a drawing or ??
    Thask guys
    It was nice to get a response at least
    R
     
  6. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    Computer does need speed input for IAC to work correctly. Also as previously said, GM did not start using electric speedo until 1990.
     
  7. Thunder

    Thunder 3/4 ton status

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    Yeah the computer needs input on speed for things like TC lockup and I believe it also has some effect on fuel curve. It will run ok without a Vss but you wil get a VSS trouble code, TC probabally wont lock up. There may be some small driveability issues like stalling or high idle and such.
     
  8. bablazer73

    bablazer73 1/2 ton status

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    My 87 has a speed sensor In the back of the cable driven speedo. 3 wires, red, green and black. Do you think you could replace with a cable driven and use that sensor for the computer??
    Just a thought.
     
  9. K5 NUTT

    K5 NUTT 1/2 ton status

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    Randy...89 was the last year of the cable driven speddo's...90-1 use a true electronic speddo with the drac module and all...87 -89 use a small greenish module on the cluster that is sort of a pulse generator...it feeds the ecm and the CC if you have it. Have all the wiring books from Helm. Suckin up overtime tomorrow but sunday before the big race i will be free to chat.

    If it was built late 89 then it could have all the 90 gizmo's...but not to worry....Howeel sells the correct 2 pulse vss for $85...then you should be fine...simple plug and play. Under the radio will be a white box...its called a DRAC....it converts the analog signal to a digital the ecm can read and the flows out to the CC...ECM..ABS...and the cluster...blue wire...circuit 824 if i member right...also signal from vss enters the cab via ecm harness and is routed thru a small metri pak connector that will be a 10 pin deal and black...then to the drac....my wifes 90 V2500 came with a non working speedo and lets say i learned the system pretty well.

    Good news is you can flash if you will the drac to adjust for tire height changes...ISS (Intstrument Sales @ Service can burn a new one for $85....they need the rear end gearing and tire circumfrance to do it...there is a post somewhere about how to clip some wires in the drac so you can skip the visit at ISS but i haven't checked out all the links and done the homework there...

    Speedo heads and Dracs are obsolete thru gm...LMC offers the correct speedo for $350....and for the same amount ISS will fix your cluster...the speedo heads are very delicate so don't finger them again....bad randy...lol.

    DW
     

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