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  •  » Temperature Gauge reads backwards

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    4/20/2017 7:34 AM  #1

    Phil42
    FYI FORD Member

    Offline

    From: Edmond, ok
    Registered: 2/10/2017
    Posts: 49

    Temperature Gauge reads backwards

    My 1965 Mustang has a problem with the Temperature gauge reading backwards.
    When the ignition is off it reads "C" correctly. When the ignition is turned on, the gauge
    needle moves up to "H" and stays there throughout the time the engine is running.
    The engine doesn't heat up..I suspect it is in the instrument wiring because I
    had the speedometer replaced because the odometer wasn't working. Before that,
    it would move from "C" to "H" and then slowly move to "C", as the engine heated up ,,which I thought
    was correct because, I hadn't driven the car in years and assumed that was the way it worked.   
    BTW..I think my instrument panel is referred to as the Falcon style.

     

    4/20/2017 9:56 AM  #2

    Michael H.
    I FYI 24-7

    Offline

    From: Laurel, MS
    Registered: 4/01/2013
    Posts: 869

    Re: Temperature Gauge reads backwards

    If the wire is grounded somewhere it will cause the gauge to read "H"... so I would trace  the wire looking for bare spots or cracks in the insulation that are grounding... or use an ohm meter to check for continuity between the wire and ground.

     

    4/20/2017 9:19 PM  #3

    MS
    Forum Originator

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    From: Canyon Lake, Texas
    Registered: 1/24/2013
    Posts: 11,721

    Re: Temperature Gauge reads backwards

    Also be sure you have the correct TEMP sender on your engine.
    The suggestion above to check the wire for a short to ground is very good advice.  If the wire grounds, the gauge will peg out.

    Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     

    4/21/2017 5:17 AM  #4

    John Ha
    I FYI 24-7

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    From: Mitchell, SD
    Registered: 4/02/2013
    Posts: 736

    Re: Temperature Gauge reads backwards

    The easiest start to your troubleshooting is to pull the wire off the temperature sender while the engine is running.  If the gauge goes back to "C" you probably either have a bad sender or the idiot light sender instead of the temperature measuring sender.  While the wire is off the sender put a voltmeter + lead on the wire and the - voltmeter lead on a good ground.  If you see either a steady 5V or a pulsing signal that averages out around 5 V your dash wiring is good.

    Founding Member of the Perpetually Bewildered Society
     

    4/22/2017 6:18 PM  #5

    50vert
    Senior 24-7 FYI Addict

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    From: QLD Australia
    Registered: 4/01/2013
    Posts: 1,356

    Re: Temperature Gauge reads backwards

    I once had the same problem on an old english ford I useta own.
    It turned out to be the oily/greasy engine, (we've all had one of them,right ....??) was providing a path to ground over the outside of the sender body. As it heated up, the conductivity of the oil/grease would change, causing erratic readings.

    Disregard if your engine is cleaner than a lot of mine were, or you use more fuel than oil. 
     

    Last edited by 50vert (4/22/2017 6:19 PM)

    "Those telephone poles were like a picket fence"
     

     

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