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67' Cj5 V6 Speedometer / Gauge Install And Grounding

Discussion in 'Early CJ5 and CJ6 Tech' started by Fred T, Mar 30, 2019.

  1. Mar 30, 2019
    Fred T

    Fred T New Member

    Knoxville, TN
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    Fellas-
    I've been radio silent for a while. Sorry. I bought a new (95 year old) house last spring and the Jeep got pushed down the priority list, but now the garage is re-organized, spring is here and the Jeep has risen back to its rightful status.
    I've struggled with my temp and fuel gauge accuracy for years, but a few weeks ago my brother in law, Maury who posts here often, found me some NOS gauges. I've read lots of posts on here about the gauges and it seems my problem may have been grounding. For now, I'm not going to ask about grounding the temp and fuel sending units, I think I can figure that out, but my questions center around grounding the gauges and speedometer itself.
    I'll try to post photos, but my speedometer housing has little cardboard "insulators" all over it. The gauges themselves have hard "cardboard-ish" backs to them and then there is another insulator between the gauges and the speedometer housing and then more behind the gauges on the back of the housing. Are all these insulators correct? Also, should I try to ground my housing to the firewall just to make sure it's grounded?
    Here are some photos:
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
     
    Last edited: Mar 30, 2019
    maurywhurt likes this.
  2. Mar 30, 2019
    62CheepJeep

    62CheepJeep Member

    Spartanburg SC
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    Pics not coming through. 404 on the link for me at least
     
  3. Mar 30, 2019
    Fred T

    Fred T New Member

    Knoxville, TN
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    Maury just helped me fix them. Thanks for letting me know.
     
  4. Mar 30, 2019
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    First point, the shell of the cluster must be grounded when the gauges are powered or you'll release the magic smoke.

    Second, the little cardboard tubes are light shields to keep the light from the bulbs on their respective indicators. These are definitely cardboard.

    Yes, you need the insulation. The gauge posts must be insulated from the cluster body. Kinda doubt the original insulators were cardboard; likely they were a cheap grade of brown phenolic (an early plastic) that looks like cardboard. They may be thin hardboard (masonite), but not cardboard. Cardboard will fall apart with moisture and age, and that will be bad. That black bar tha goes across is at 5V always and must be insulated, and the other post goes to the gauge sensor and must be insulated. If the original insulators are falling apart, I would make new ones from some plastic, not cardboard. A Tupperware lid would work well, and you can cut it with scissors. You can buy phenolic sheet which would be most like the original, I'd think, but I expect any plastic will do.

    https://www.amazon.com/dp/B0013HKZTU/ref=biss_dp_t_asn
     
    Last edited: Mar 30, 2019
    Lee Bennett likes this.
  5. Mar 30, 2019
    Fred T

    Fred T New Member

    Knoxville, TN
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    Thanks for the response! Are you saying that both the gauges should have essentially three layers of insulation? First the insulation that is integral to the back of the gauge, second the insulation that is attached to the inside of the speedometer housing and third the insulation on the back of the speedometer housing?
    It also sounds like maybe you're saying the little posts on the back of the gauge cannot be touching the housing at all?
     
  6. Mar 30, 2019
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    Yes, absolutely. It would help to read about the circuit. Gauge Repair Information

    You understand that there is a constant voltage regulator CVR in the fuel gauge? The ground for that voltage regulator goes through the gauge body to the cluster housing and to the dash. The other grounds are through the senders. If you fail to ground the CVR, it will not regulate and the gauges will burn up. Unlikely the CVR ground is responsible for inaccurate readings.

    Could be the aftermarket part makers added more insulation, but I would not leave out any of it. May be excessive, but maybe not.
     
    Last edited: Mar 30, 2019
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  7. Mar 30, 2019
    Lee Bennett

    Lee Bennett Banned

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    Thanks. I think you may have just fixed the problem I have been having. Donation coming!
     
  8. Mar 30, 2019
    Lee Bennett

    Lee Bennett Banned

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    If the 12v terminal on the fuel gauge Is not connected, what would be the effect? Will it cause a no output from alternator?
     
  9. Mar 30, 2019
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    No effect on the alternator or alternator light, I would expect. I'd have to check the wiring diagram (which I do not have) to comment on the alternator light circuit. The gauges will stay at zero.
     
  10. Mar 30, 2019
    Lee Bennett

    Lee Bennett Banned

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    I'll have to check that. I have everything new - all switches, cluster, harness, alternator, ignition, and regulator. Engine starts but alt light stays on. I guess the wiring harness is letting the gauges work.
     
  11. Mar 30, 2019
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    Which alternator?

    I would not drive that Jeep without a front bumper. Ok for a test drive, but the frame horns need the reinforcement of the bumper.
     
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  12. Mar 30, 2019
    Lee Bennett

    Lee Bennett Banned

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    She's still sitting. Look at the new bumper! Wish I could drive it. Need an alternator to work first. The alternator is a DL 7091. That's what matches OEM.
     

    Attached Files:

  13. Mar 30, 2019
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    Woohoo!

    Just wondered whether it's the original alternator or a Delco. I understand how the light works on a Delco, not so much for the Motorola. I expect the light sits between the regulator and the ignition switch, and the regulator line should go high when the alternator is charging.
     
  14. Mar 30, 2019
    Lee Bennett

    Lee Bennett Banned

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    It is the motorola design. What do you mean by "regulator line should go high?
     
  15. Mar 30, 2019
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    High is +12V, low is ground potential. When you start up, the regulator end is at ground potential (low), the circuit conducts and the bulb lights. As the alternator starts charging, the voltage of the regulator end rises (goes high) so that there is no longer current from the ignition switch to the regulator, and the light goes out.
     
  16. Mar 30, 2019
    Lee Bennett

    Lee Bennett Banned

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    Please help me make sense of this. 1. With the engine running, should the field terminal be in a voltage output phase, or should it show grounded? 2. What would the 12v switched terminal on the back of the gauge be for?
     
  17. Mar 31, 2019
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    Maybe my scribbles will help:

    upload_2019-3-31_9-36-26.png
     
  18. Mar 31, 2019
    Fred T

    Fred T New Member

    Knoxville, TN
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    This electrical stuff is so tedious.
    I did all the above and ran a ground wire from my fuel sending unit to the body where I have other things grounded and both gauges went to full and hot pretty quickly. Any new helpful ideas? Thanks again for any suggestions!
     
  19. Mar 31, 2019
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    Follow the link I posted above and test voltages. The first thing is always test voltages. You need a good multimeter and need to know how to use it. Recall that the cluster shell must be grounded during the tests!

    Next if everything checks out, I would substitute resistors for the sending units and see what readings I get. This is detailed in the TSM.

    If the CVR is defective, you will get a contant 12V at the black bar between the gauges. There is a ground for the CVR, shown in the pictures and diagrms shown here Gauge Repair Information (also posted above). If the CVR is grounded as shown and still does not work, substute a 7805 or 7806 voltage regulator integrated circuit for the factory CVR. This is an excellent upgrade IMO, and makes the circuit safer (no magic smoke if the cluster ground is not present). Search old posts to learn about this.
     
    Last edited: Mar 31, 2019
  20. Mar 31, 2019
    maurywhurt

    maurywhurt Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    Please forgive if this seems incredibly elementary, but I'm trying to help Fred fix his gauges, and at this point neither of us have figured this out.

    It appears that all of the terminals on the backs of both the fuel and temp gauges are on the hot side. If Fred and I are correct in interpreting the chart below (and the chart itself is correct), terminal #1 is 12v. Terminals #2 and #12 are stepped down to 5 volts by the internal regulator in the fuel gauge. Terminals #3 and #11 connect to the respective fuel and temp sending units.

    Knowing that the cluster housing must be well grounded, we're wondering....

    How are the temp gauge and the internal voltage regulator in the fuel gauge grounded to the cluster housing?



    [​IMG]
     
    Last edited: Mar 31, 2019
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