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Thread: Temperature gauge

  1. #1
    Join Date
    Feb 2009
    Location
    Warrimoo, Blue Mountains, NSW
    Posts
    312

    Temperature gauge

    Having got my nice new engine turning over, I need to solve a couple of other problems.

    When I turn the ignition on and start up the engine, the temperature gauge starts off low, then rapidly climbs to maximum reading.

    There's no problem with the engine temperature, I can put my hand on the top of the radiator, and I can feel the radiator temperature lowering as I check out the radiator core lower down.

    The temperature sender is part 560794, and the gauge is part 560746. They should match up.

    The resistance across the gauge is 60 ohms. The resistance of the sender when cold is 390 ohms, and 60 ohms when hot. The body of the sender is well earthed, and it's brand new.

    Can anyone with a multimeter confirm that those readings are correct?

    Can anyone come up with some other trouble-shooting approach?

    Thanks, Peter

  2. #2
    Join Date
    Jan 1970
    Location
    Central West NSW
    Posts
    20,228
    Assuming you are talking about the factory temperature gauge fitted 1967 on, (and the part numbers confirm this) then the problem is most likely that the voltage stabiliser is :-

    1. Missing or not in the circuit
    2. not properly earthed (on this model it is mounted on the bulkhead and relies on the mounting and the bulkhead for earthing)
    3. Faulty.

    (in that order)

    The voltage stabiliser gives 10v nominal, but this is actually an intermittent 12v switched on and off by a bimetal strip with a period of several seconds.

    If the stabiliser is present and working (confirm by switching on the ignition and check voltage at the sender, should go on and off, also is the fuel gauge behaving), you may have a problem with manufacturing tolerance of the gauge and/or sender. I had this, so the normal running temperature was only just below the hot mark. I simply experimented with small resistors until I found one that gave the normal reading when in series with the sender.

    John
    John

    JDNSW
    1986 110 County 3.9 diesel
    1970 2a 109 2.25 petrol

  3. #3
    Join Date
    Feb 2009
    Location
    Warrimoo, Blue Mountains, NSW
    Posts
    312
    Thanks John. There's no voltage stabiliser in the circuit - this is running on a test bed, see the circuit diagram attached. I'm assuming the voltage stabiliser in the alternator will be adequate for the job.

    If my arithmetic is correct, the resistor would need to be 2/10*(60+390) ohms, say 10 ohms at 5%?

    Peter
    Attached Images Attached Images

  4. #4
    Join Date
    Feb 2009
    Location
    Warrimoo, Blue Mountains, NSW
    Posts
    312
    Thanks again John - a 39 ohm resistor did the job.

    Peter

  5. #5
    Join Date
    Jul 2006
    Location
    East-South-East Girt-By-Sea
    Posts
    17,654
    Peter

    The voltage stabiliser/resister for the guages is usually screwed to the back of the instrument cluster. Its a little rectangular metal box with 3 Lucar (blade) connectors pointing out.

    Diana

    You won't find me on: faceplant; Scipe; Infragam; LumpedIn; ShapCnat or Twitting. I'm just not that interesting.

  6. #6
    Join Date
    Feb 2009
    Location
    Warrimoo, Blue Mountains, NSW
    Posts
    312
    Thanks Diana, that sounds like part 148876, from a Series 3. Do you think it's required, or is it an optional extra?

    Peter

  7. #7
    Join Date
    Jan 1970
    Location
    Central West NSW
    Posts
    20,228
    The voltage stabiliser is not optional. The reading of the gauge depends on the supply voltage and the resistance of the sender. The alternator regulator limits the maximum voltage to about 14v, but the voltage with the engine idling after starting is probably less than 12v, and this variation will make the readings pretty meaningless. The stabiliser from the Series 3 and 2a is the same except that the Series 2a one does not have a connection for earth, but relies on being earthed by its mounting screws.

    John
    John

    JDNSW
    1986 110 County 3.9 diesel
    1970 2a 109 2.25 petrol

  8. #8
    Join Date
    Feb 2009
    Location
    Warrimoo, Blue Mountains, NSW
    Posts
    312
    Thanks John. I'd better set about getting one. Can you tell me what the I and B markings on the pins mean?

    Peter

  9. #9
    Join Date
    Jan 1970
    Location
    Central West NSW
    Posts
    20,228
    Quote Originally Posted by peterg1001 View Post
    Thanks John. I'd better set about getting one. Can you tell me what the I and B markings on the pins mean?

    Peter
    Not absolutely certain - I'd have to look at one to confirm, but I think that B is for Battery, and I is for Indicator or gauge.

    John
    John

    JDNSW
    1986 110 County 3.9 diesel
    1970 2a 109 2.25 petrol

  10. #10
    Join Date
    Dec 2009
    Location
    Canberra
    Posts
    1,551
    Quote Originally Posted by JDNSW View Post
    Not absolutely certain - I'd have to look at one to confirm, but I think that B is for Battery, and I is for Indicator or gauge.

    John
    yup

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