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Help with instrument cluster - 77 K10

Discussion in 'Gauge, Speedo & Instrumentation' started by Dleslie212, Sep 13, 2019.

  1. Dleslie212

    Dleslie212 Junior Member

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    Location:
    Phoenix
    First Name:
    Dustin
    Truck Year:
    1977
    Truck Model:
    K10
    Engine Size:
    5.7L 350
    I am trying to buy a new printed circuit board for my 77 K10. I had LMC Truck email me a picture of the boards they have for 77, but it doesn't match up to what I have. I found a number on my old board, and Googling brings this up, which is exactly what mine looks like.

    https://www.summitracing.com/parts/ado-25044897

    From what I can tell, this particular board was for 85-86. So I'm thinking somebody swapped out the gauge assembly at some point.

    I also found this:

    https://www.ebay.ca/itm/73-87-Chevy...ash=item4208ad8395:g:Y64AAOSwtYJdV1Xg&vxp=mtr

    Which is exactly what my cluster housing looks like, minus the hole for the clock at the bottom left - mine is just blank plastic.

    My question is, which circuit board should I get? The one for the 77? Would that even fit on my cluster housing if the cluster housing is from 85-86 (I don't know that it is)
     
  2. chengny

    chengny Full Access Member

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    Truck Year:
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    Truck Model:
    K3500
    Engine Size:
    350/5.7

    It looks like that bucket (case) shown in the link is part number 25051838. That P/N shows as used in the C/K 1,2 & 3 series for model years 1983 & 84. It appears to accept printed circuit with P/N 25044897 (C/K 1, 2 &3 without tach). The only thing that doesn't seem correct is that it is described as not having a clock?
     
  3. Dleslie212

    Dleslie212 Junior Member

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    Truck Model:
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    Engine Size:
    5.7L 350
    That's correct, the spot on the bottom left where the clock would be has not been punched out. So should I be getting the circuit board for a 83-84? Or should the 77 board work on the cluster housing that I have? Here are a few pics I just took of what I pulled out

    https://imgur.com/O5Y4S4Q
    https://imgur.com/RJWYPt8
    https://imgur.com/Hik0q2d

    Edited to add:

    Here is the picture LMC Truck sent me of the 77 board, their part number is 38-8037
    https://imgur.com/xPd8JK6
     
    Last edited: Sep 14, 2019
  4. Dleslie212

    Dleslie212 Junior Member

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    First Name:
    Dustin
    Truck Year:
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    Truck Model:
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    Engine Size:
    5.7L 350
    I am adding a few more pics I took of the cluster wiring harness, hoping somebody can point me in the right direction. I also read in a post from here that the 77 only came factory with a mechanical oil pressure gauge - electric didn't start until 78. Mine is electric, and is one of the only gauges that actually DO work. So now I'm thinking the harness must have been changed out as well? If that's the case, I'm assuming I should just get whatever works for the harness year-wise, so that I don't have to replace the harness again?

    Also, I've found this: https://www.classicparts.com/1981-87-Instrument-Cluster-Circuit-Chevy/productinfo/24-489GT/

    Which looks exactly like the circuit board I pulled off - but not the same as what LMC Truck has listed for the same year? Anybody know why?

    Here are a few pics of my cluster wiring harness -

    https://imgur.com/miBCynz
    https://imgur.com/JfCZ4oT
    https://imgur.com/1hwrX2k
     
  5. chengny

    chengny Full Access Member

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    I would stick with the 25044897 circuit. The connectors for the 77 and the 81-84 are not compatible. There do not even use the same number of tabs. That and the fact that the circuit for the 81 - 84 shows as correct (see below):

    Pages from Group 9 - Body  Mounts & AC.JPG

    To revert back to the 77 harness would require some serious re-pinning.
     
  6. Dleslie212

    Dleslie212 Junior Member

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    Truck Year:
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    Truck Model:
    K10
    Engine Size:
    5.7L 350

    My main concern is the possibility that the previous owner threw 81-84 gauge assembly in there, without replacing the harness. Can anybody tell from the pictures I posted whether that is the harness for a 77, or the harness for an 81-84?
     
  7. C10MixMaster

    C10MixMaster Full Access Member

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    First Name:
    Ben
    Truck Year:
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    Truck Model:
    C10 BIG10
    Engine Size:
    350
    The clusters from 73-91 all used the same connector they are just pinned different. If the oil gauge works the some one added wiring or replaced it with a newer harness. here's the pinouts for both. I would use the circuit board that matches the gauges These are real easy to repin..



    image2.JPG image3 (2).JPG
     
  8. Dleslie212

    Dleslie212 Junior Member

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    Engine Size:
    5.7L 350
    I actually saw this table a few days ago, but some things don't line up - my dark blue wire is on pin 12, which is not listed on that table anywhere. Dark blue only shows as 1, 3 or 5 on the table. Also, I have two pink wires at pin 18, and the table doesn't show pink at pin 18 anywhere. Any suggestions?
     
  9. Dleslie212

    Dleslie212 Junior Member

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    Truck Year:
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    Truck Model:
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    Engine Size:
    5.7L 350
    Here are the colors going to the pins in the harness. There are some pictures above if it helps any

    Pin -------- Color

    1 - Light Green
    2 - Grey
    3 - Black
    4 - Pink w/ black stripe
    5 - Brown (maybe tan, hard to tell if the wire is just discolored)
    6 - Pink
    7 - Pink
    8 - Black
    9 - Dark Green
    10 - Black
    11 - Light Blue
    12 - Dark Blue
    13 - Yellow
    14 - Blank, no wire
    15 - Blank, no wire
    16 - Pink w/ black stripe
    17 - Brown w/ white stripe + tan w/ white stripe (two wires in pin 17)
    18 - Pink + Pink (two wires in pin 18)

    I just can't find anything in the table above that matches.
     
  10. C10MixMaster

    C10MixMaster Full Access Member

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    Truck Model:
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    Engine Size:
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    looks closest to the 78-82 harnesses . when parts get mixed from different years these things happen. No telling exactly what the previous owner did and its possible there are others variations not on the table above. there are other wires not shown also, for example i believe one of the pink and black striped wires are for the seat belt light. The color codes seam remained fairly consistent. When i swapped a 91 cluster into my 77 i went through this. What i ended up doing tracing the circuits on the cluster, for example the gas gauge wire traced it back to pin 7 and did that for all 18 pins. then i used the chart above for a reference on the wiring. then repinned it to match. If your 77 has blade fuses and not glass fuses the harness is not original and has been updated.
     
  11. Dleslie212

    Dleslie212 Junior Member

    Posts:
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    Joined:
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    First Name:
    Dustin
    Truck Year:
    1977
    Truck Model:
    K10
    Engine Size:
    5.7L 350
    It does have blade and not glass. I just got finished taking a look at all the wiring - it's is an absolute rat's nest. I don't know how I'm going to get that sorted out.
     

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