Like to put a stock tach in my 88 Blazer ?

Discussion in 'Tech Discussion' started by JTWard, Jul 2, 2018.

  1. JTWard

    JTWard Member

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    What do I need to do this job ? I bought a good instrument cluster off ebay with a tach, and I already have a good housing, so I bought a printed circuit for a Blazer with a Tach, and dam% sure their different. One is 2 leads short of all 18, it's only got a gas gauge and the 18 leads go I think to the tach which would of been in the gas gauge space on the cluster. What do you think ? 1988 Blazer dashboard w. tach.jpg s-l275.jpg

    SANY0831.JPG
     
  2. bucket

    bucket Super Moderator Staff Member

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    What year cluster did you buy? You need a '78 or newer cluster to swap in. The tach harness is separate from the printed circuit.
     
  3. JTWard

    JTWard Member

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    It was listed as 1979 to 1990. I have a new oil pressure gauge and the overall Lt. Blue gauge cluster housing is in very good condition. Yet it has an odd gauge in it. I'm not going to use it, but I've never seen one and I'm wondering what it is. But what I need to know is what do I need for this conversion. Thank you !
     
  4. bucket

    bucket Super Moderator Staff Member

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    So I'm guessing you have a cluster from a medium duty truck then? Is your fuel gauge built into the tachometer?

    If its a cluster from a C50-70 truck, all bets are off as far as wiring pinouts go. You will just have to trace the contacts on your stock cluster and your new cluster, then compare and see what pins need moved around in the connector or what wires need added in.
     
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  5. roundhouse

    roundhouse Full Access Member

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    Some had vacuuum gauges and some had a air pressure gauge for the brakes

    The printed circuit changed a lot over the years

    You just have to follow the circuit and see where it goes

    You can make a tool to pull the wires out of the main plug and move them
     
  6. JTWard

    JTWard Member

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    SANY0851.JPG New grid.JPG SANY0866.JPG SANY0850 (1).JPG SANY0851.JPG New grid.JPG SANY0866.JPG
    It's a 1986, and I think it was a diesel. I don't know what the bottom left gauge is and upon looking at the LCM catalog, I found I needed a replacement base/cluster holder and I bought 6 more of the clips that snap on holder and the gauges snap into the holder and make contact with the grid. I have another question, would you replace the dash lights with LED's SANY0180.JPG
     
    Last edited: Jul 7, 2018
  7. 1987 GMC Jimmy

    1987 GMC Jimmy Full Access Member

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    I’ll chime in. I use the Silverstar incandescent bulbs in my clusters. They do a good job, and there’s a considerable improvement in the backlit square body cluster where I didn’t see as much in a postlit cluster (my Caprice). Here’s a pic from the night I did them.

    914C5161-E103-4FD8-B234-CAF888D573EB.jpeg
     
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  8. JTWard

    JTWard Member

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    So let me have it, the dash cluster and tach are no good for my 88 Silverado K5 Blazer 350 V8 ?
     
  9. bucket

    bucket Super Moderator Staff Member

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    You can make those work, you just have have to trace where all the contacts end up in the harness connector compared to your stock cluster, then re-pin wires if it's needed to match it up.

    The printed circuit you bought will not work however. It is for the light duty trucks with a fuel gauge in the lower left and no gauge built into the tach.

    You have a medium duty truck cluster with a fuel gauge in the tach, and an air pressure gauge in the lower left corner.
     
  10. bucket

    bucket Super Moderator Staff Member

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    I also just noticed that your new cluster has an ammeter gauge instead of volts. If not rewired correctly, it can cause a fire.

    Personally, I'd modify the stock cluster to use that nice tach/fuel combo gauge. Chances are good that it was an 8 cylinder too, rather than a 4 or 6 cyl diesel. So as long as it still works, it shouldn't need calibrated.
     
  11. JTWard

    JTWard Member

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    SANY0851 (1).JPG Yeah, it's got a SANY0849.JPG 4000 RPM tach and the gas gauge is in the tach on the bottom. The more I investigate it I starting to think this isn't going do-able. Maybe a 'A' pillar tach ?
     
    Last edited: Jul 9, 2018
  12. bucket

    bucket Super Moderator Staff Member

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    There's a company that makes a drop-in tach that looks factory. It has the fuel gauge in it too. All you have to do it run a tach harness which is very easy.

    I just can't remember the name of the company. But there's been threads about it here in the past.
     
  13. Craig 85

    Craig 85 Supporting Member Supporting Member

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    It was GM Sports. Frankenchevy just called them about 2-3 weeks ago. They told him the man making the tach died and they don't know what their future plans are. The website says on backorder until further notice.
    http://www.gmsports.com/trucks

    On my last truck I mounted the tach on the column Autogage 3 3/4" #2300. When I pulled it into gear, it would center in the dash. On my '85 I'm doing the same thing, but I'm using a 2 3/4" Autogage #2306. I also put a green filter on the bulb.

    79 GMC 4.JPG
     
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  14. dvdswan

    dvdswan Full Access Member

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    So what do you plan on doing with the cluster?
     
  15. roundhouse

    roundhouse Full Access Member

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    I would just cut out your existing cluster to fit the tach

    And re pin the wires or make some that go to the fuel gauge

    That tach is from a diesel if it’s a 4000
    That were usually driven from the alternator ?
     

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