1. Welcome to Tacoma World!

    You are currently viewing as a guest! To get full-access, you need to register for a FREE account.

    As a registered member, you’ll be able to:
    • Participate in all Tacoma discussion topics
    • Communicate privately with other Tacoma owners from around the world
    • Post your own photos in our Members Gallery
    • Access all special features of the site

temp gauge pegged in red zone- but it's not hot !

Discussion in '1st Gen. Tacomas (1995-2004)' started by lvs2rock, Jun 17, 2020.

  1. Jun 17, 2020 at 3:26 AM
    #1
    lvs2rock

    lvs2rock [OP] Well-Known Member

    Joined:
    Jul 24, 2011
    Member:
    #60463
    Messages:
    187
    N. Cali
    Vehicle:
    96 Taco 2RZ-FE auto
    FINALLY replaced temp sending unit and harness connector (to instrument cluster) after 2 1/2 years driving with 'broken' temp gage- wired it in last week-it was working fine but the installation was 'incomplete' until today, when I was able to use my heat gun on the marine heat-shrink tubing with which I'd covered the splice. Later, started engine to warm it up and confirm I'd eliminated an unrelated issue been working on for days-some few minutes later I looked at the dash and the temp gage needle was pegged all the way in the red 'hot' zone. Shut it off (half-panic-stricken)-let cool completely, needle back down below 'c'-turned key on, needle instantly jumped back into red 'H'. Other than the temp gage there were no other indications of overheat/running hot.
    Did I trigger this by using the heat gun on the wires? Now what do I do?
    Thanks in advance for your input.
     
    cruiserguy likes this.
  2. Jun 17, 2020 at 6:44 AM
    #2
    Glamisman

    Glamisman Well-Known Member

    Joined:
    Oct 22, 2016
    Member:
    #200436
    Messages:
    3,011
    Gender:
    Male
    disconnect the wire from the temp sensor and see if the gage still pegs "H", if so, the wire for the gage is shorted to ground somewhere.
     
    cruiserguy and lvs2rock [OP] like this.
  3. Jun 17, 2020 at 10:14 AM
    #3
    lvs2rock

    lvs2rock [OP] Well-Known Member

    Joined:
    Jul 24, 2011
    Member:
    #60463
    Messages:
    187
    N. Cali
    Vehicle:
    96 Taco 2RZ-FE auto
    I'll try that, thanks for taking the time to answer.
     
  4. Jun 17, 2020 at 2:58 PM
    #4
    lvs2rock

    lvs2rock [OP] Well-Known Member

    Joined:
    Jul 24, 2011
    Member:
    #60463
    Messages:
    187
    N. Cali
    Vehicle:
    96 Taco 2RZ-FE auto
    so I did as suggested: unplugged, plugged back in. Took a moment or so but gage pegged 'H" again. That sensor only has one wire, AFAIK the sensor itself provides the 'ground' connection where it's threaded into the block. D'ya think I somehow fried the sensor or .....?
     
    cruiserguy likes this.
  5. Jun 17, 2020 at 6:32 PM
    #5
    cruiserguy

    cruiserguy Well-Known Member

    Joined:
    Jul 31, 2016
    Member:
    #193416
    Messages:
    19,072
    Gender:
    Male
    First Name:
    Elijah
    SLC
    Vehicle:
    2000 ext cab, 2.7L, auto, 4x4
    So just to make sure we understand correctly, you originally did a temporary install of the new sending unit and the temp gauge marked where it should around the halfway mark. Couple weeks later you came back to clean up some wiring of the sensor, adding heat shrink wrap to wiring. Reassembled and jumps to H quickly again without engine overheating.
    If so, I think the heat of the torch must've affected the temp send unit.
    Well yeah now that I think about it. That sensor only sees like up around 200-230 degrees huh? I guess heat from a torch could easily affect it.
    Do you have a digital multi-meter?
     
    lvs2rock [OP] likes this.
  6. Jun 18, 2020 at 7:52 AM
    #6
    Glamisman

    Glamisman Well-Known Member

    Joined:
    Oct 22, 2016
    Member:
    #200436
    Messages:
    3,011
    Gender:
    Male
    I am sorry if I didnt explain fully what I wanted you to do.

    The temp sesnor is nothing more variable resistor whos resistance changes with temperature. If you take the wire off the sensor and ground it the coolant gage should go to H. If you leave it disconnected is should go to C. If the wire is disconnected and the gage still shows H then there is a problem with the gage or the wiring for the gage.
     
  7. Jun 18, 2020 at 11:03 AM
    #7
    lvs2rock

    lvs2rock [OP] Well-Known Member

    Joined:
    Jul 24, 2011
    Member:
    #60463
    Messages:
    187
    N. Cali
    Vehicle:
    96 Taco 2RZ-FE auto
    thanks so much for the replies guys! Will follow instructions exactly and return here...…..
     
    cruiserguy and Black DOG Lila like this.
  8. Jun 23, 2020 at 4:56 AM
    #8
    lvs2rock

    lvs2rock [OP] Well-Known Member

    Joined:
    Jul 24, 2011
    Member:
    #60463
    Messages:
    187
    N. Cali
    Vehicle:
    96 Taco 2RZ-FE auto
    yup, evidently I fried the sensor.........(cursing, tryin' to kick my own behind).................and suddenly the truck won't start.

    edit:
    d'oh!
    Rookie move: Loose ground wire(s)=engine no start. Took me a few minutes of backtracking to figure out :facepalm: that although I'd put the engine ground connections back in place (after fixing the vacuum leak at the fuel injector) I had failed to properly tighten them down.
     
    Last edited: Jul 20, 2020
    cruiserguy likes this.

Products Discussed in

To Top