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Stewart Warner Green Line Tach on a 1965 CJ5 F134

Discussion in 'Early CJ5 and CJ6 Tech' started by Greevesman, Mar 7, 2015.

  1. Mar 7, 2015
    Greevesman

    Greevesman Member

    Napa, Ca
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    I bought one on ebay as it was sort of the right vintage for my jeep. It was supposed to be 4 cyl, 5000 rpm which I thought would be perfect for the F134, It arrived and had an original SW sender attached to the back of the unit. I connected it up and it indicated exactly half the rpm of my shop test instrument. Fellow couldn't explain so I sent it back. He tested it on two of his testers and found that the sender was probably weak so he got someone to produce a small circuit board sender that was supposed to take care of the problem. When it came back it was sort of correct but the needle was bouncing around like crazy. I rigged up a shielded signal wire and grounded the shield but it still bounced around. The seller said I needed a "tach filter" which he sent me. Small black cube with a ground wire and signal in and signal out. Connected it up and performance is better but the needle still bounces around mostly at low rpm.
    At low RPM there is bouncing in time with the brake lite being energized and de energized as well as the turn signal operating. High RPM it smooths out. There must be electronic noise in the power supply which I have connected to the ignition switch? Does anyone know of a way to clean up the source of power?
    Thanks in advance.
     
    Greevesman, Mar 7, 2015
    #1
  2. Mar 7, 2015
    Howard Eisenhauer

    Howard Eisenhauer Administrator Staff Member

    Tantallon, Nova...
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    Sender? Any tach I ever had just ran a wire to the points & you set a switch on the tach for 4, 6 or 8 cylinders.

    Is your ignition stock?

    H.

    EDIT- OK, did a little research, got temporarily miss-lead by the "new" green line tachs but eventually found my way - WOW- those things are "Old School".

    An electrical tach is what's known as a "Frequency to Voltage" converter- the more pulses it receives in a period of time the higher the voltage output which is fed to a voltmeter with a scale printed in RPM instead of volts. What's going on here is that instead of putting the converter & meter in a single case the conveter is in a separate box (sender) & the meter is a panel mount unit. The sender is , probably originally, electro-mechanical designed for for a specific number of cylinders like the one in link provided by 1960willyscj5 below, modern ones (anything designed after the early 60's) would use electronic converters with a selector switch.

    Your problem is probably that your new electronic "sender" is sensitive to the supply voltage, you must be feeding it from someplace where it's seeing voltage fluctuations (probably caused by degraded wiring/connections). You could try a 12 volt regulator to feed the sender (which may throw the calibration off) , or power it with a lead directly to the battery but you may find that any battery voltage changes will change your rpm reading.
     
    Last edited: Mar 7, 2015
    Howard Eisenhauer, Mar 7, 2015
    #2
  3. Mar 7, 2015
    1960willyscj5

    1960willyscj5 Well-Known Member

    Mesa, Arizona
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    Even not stock ignitions with tachs would work that way.

    Mine on my '60 with the pertronix in it is very accurate.

    Did you maybe get one for a diesel engine? Most of those are mechanical, meaning they run on a cable like the ones on motorcycles.
     
    1960willyscj5, Mar 7, 2015
    #3
  4. Mar 7, 2015
    1960willyscj5

    1960willyscj5 Well-Known Member

    Mesa, Arizona
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    1960willyscj5, Mar 7, 2015
    #4
  5. Mar 7, 2015
    Keys5a

    Keys5a Sponsor

    Florida Keys
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    I too have never seen a tach that needs a sending unit as the ones I am used to run from a wire off the distributor.
    On my old British sports cars, there is a "voltage stabilizer" that all the dash guages feed from. I'm not really sure how it functions, but my guess is a capacitor?
    -Donny
     
    Keys5a, Mar 7, 2015
    #5
  6. Mar 7, 2015
    Greevesman

    Greevesman Member

    Napa, Ca
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    This Tach is from the early to mid 60s. The sending unit is either mounted in the chrome can on the back of the gauge or could be remote. This one was on the back of the instrument in the chrome can.
     
    Greevesman, Mar 7, 2015
    #6
  7. Mar 7, 2015
    scoutpilot

    scoutpilot Member

    Asheboro, NC
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    Look up Sun Tachometer on eBay.
     
    scoutpilot, Mar 7, 2015
    #7
  8. Mar 8, 2015
    Greevesman

    Greevesman Member

    Napa, Ca
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    Why Sun? This is a Stewart Warner/ Sun senders had batteries that leaked and corroded the sender.
     
    Greevesman, Mar 8, 2015
    #8
  9. Mar 9, 2015
    Walt Couch

    Walt Couch sidehill Cordele, Ga. 2024 Sponsor 2023 Sponsor 2022 Sponsor

    cordele, Ga.
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    Am I reading this correctly that you have the Tac working correctly but the Tac is effected by voltage blips?
     
    Walt Couch, Mar 9, 2015
    #9
  10. Mar 9, 2015
    Greevesman

    Greevesman Member

    Napa, Ca
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    That seems to be the case.
     
    Greevesman, Mar 9, 2015
    #10
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