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Got a head scratcher...

Discussion in 'Early CJ5 and CJ6 Tech' started by scoutpilot, Sep 10, 2014.

  1. Sep 10, 2014
    scoutpilot

    scoutpilot Member

    Asheboro, NC
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    '69 CJ5, F4-134, New wiring harness, properly installed. new gauge cluster. Temp gauge doesn't register and oil press idiot light won't go out. I removed the dash board. I cleaned the four mounting posts for the cluster. I cleaned the nuts holding the cluster to the dash. I performed a resistance test on the sender in the block and as heat went up resistance went down. I took the lead for the temp gauge and with the key on, momentarily grounded it. The gauge pegged hot. Hooked it all back up and zilch, nada, zip. The block is grounded to the frame. I had just recently swapped motors so the grounds were cleaned. I think the oil press sending unit may be bad, but I have an analog gauge to reassure me that pressure is there. What am I missing?
     
  2. Sep 10, 2014
    Walt Couch

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

    cordele, Ga.
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    So I take it the fuel gauge is working or the temp gauge would not have gone up when grounding the temp sender wire? So what gauge cluster did you install?
     
  3. Sep 10, 2014
    Twin2

    Twin2 not him 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Virginia Beach, VA
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    that's a big problem with aftermarket temperature sending units . some will read correct and most won't .when I am wasting time in junk yards . I'll grab a few for the things I drive . just for spares . last time the gauge quit working in my work car ( 88 ford ranger ) went to all three auto stores here in town , not one would read correct . so next trip to junk yard fixed that . yes to what walt said . what aftermarket cluster did you use . now that the temperature needle makes a full swing . leads me back to sender . as to oil idiot light if unhooked it should go out . sender again . could you still take senders off other engine and try them
     
  4. Sep 10, 2014
    scoutpilot

    scoutpilot Member

    Asheboro, NC
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    I got the cluster from Walcks. This is number two. First one didn't work at all. Going to put in new oil press sender and swap temp senders again. The bushing for the temp sender is steel, that makes a difference. Oh, and speedometer reads about 10-12mph high.
     
  5. Sep 10, 2014
    termin8ed

    termin8ed I didn't do it Staff Member

    Mason, MI
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    Is the oil sender a switch or sensor? If its a resistive sensor the light may never go out. Just dimmer. I would assume its a switch of some kind?
     
  6. Sep 10, 2014
    scoutpilot

    scoutpilot Member

    Asheboro, NC
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    Yes. A pressure switch. Late sixties motor.
     
  7. Sep 11, 2014
    termin8ed

    termin8ed I didn't do it Staff Member

    Mason, MI
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    Do you know what the spec is for it? From same motor or somethjng laying around?
     
  8. Sep 11, 2014
    scoutpilot

    scoutpilot Member

    Asheboro, NC
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    taken off old f-head.
     
  9. Sep 11, 2014
    Walt Couch

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

    cordele, Ga.
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    Yep oil is just a pressure on/off switch that opens at around 5 lbs pressure and turns out the light. The temp sensor has to be immersed in coolant fluid or it will not work. Also will not work in steam. Make sure there is no air lock in system.
     
  10. Sep 11, 2014
    scoutpilot

    scoutpilot Member

    Asheboro, NC
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    I'll b burp it this afternoon. Thanks Walt!
     
  11. Sep 11, 2014
    kamel

    kamel Senior Curmudgeon

    Erlanger, Kentucky
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    I had a brand new oil sender that I put in a freshly rebuilt engine and a couple of months later the oil light came on intermittantly. Put in a new sender unit and it works fine now.

    The oil sender is simply a pressurer switch that is normally closed. Not much rocket science here.

    The temp sender is a variable resistance unit and I'm sure that the repro senders aren't calibrated to the jeep engine, so they will read all over the map. If you could put in a mechanical temp gauge that would tell the correct story.
     
  12. Sep 13, 2014
    scoutpilot

    scoutpilot Member

    Asheboro, NC
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    OK. Double checked everything. Replaced Oil Pressure sending unit with a new one. Replaced Temp sender with known good one. Still no temp reading or idiot light shut off. Where to now?

    One other thing I've stumbled on to. I've been reading analog gauges for so long, I didn't notice until now that the AMP idiot light does not come on when I turn the key to either ON or ACC. A clue?
     
    Last edited: Sep 13, 2014
  13. Sep 13, 2014
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Hills of NH
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    Sometimes the idiot lights get swapped around and end up in the wrong locations. Are you sure yours are all in their correct places?
     
  14. Sep 13, 2014
    termin8ed

    termin8ed I didn't do it Staff Member

    Mason, MI
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    Is the wiring good? With switch disconnected can you jumper the wire to the switch to (assuming) ground to get the light to turn on and off?
    Verified the oil pressure with gauge?
    If yes then has to be bad oil switch
     
  15. Sep 13, 2014
    termin8ed

    termin8ed I didn't do it Staff Member

    Mason, MI
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    If the light stays on when switch is disconnected theres a short to ground somewhere
     
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