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  1. #1

    Default Fireball 225 Temp Sender for '58 Century?

    My Fireball 225 V8 is installed in a 1958 Century Arabian. It has two temperature sending units to the boat's two temperature gauges. One sender produces correct temperature readings and other does not read at all because it is not the correct sender for these gauges.

    The “correct” sender has no manufacturer’s markings on it at all. Other than its appearance (see photo), its only distinguishing characteristic is an initial resistance reading of ~ 180 Ohms when the ambient air temperature is ~ 75 degrees F prior to engine start.

    Any information leading to my locating and purchasing a “correct” sender would be appreciated!

    Fritz

  2. #2

    Default Re: Fireball 225 Temp Sender for '58 Century?

    This is the photo referenced in my post above: Click image for larger version. 

Name:	sender email photo.jpg 
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    This morning, I developed a profile of the resistance readings as the engine warmed to operating temperature. The Outside Air Temperature (OAT) was 50 degrees F. at the time. The other temperatures were according to the dash gauge. Here are the results:

    Temperatures Ohms
    ------------- -----
    50 295
    100 100
    130 55
    160 45

    I hope this is helpful to anyone with a sender that might be a candidate.

  3. #3
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    6,764

    Default Re: Fireball 225 Temp Sender for '58 Century?

    FWIW, the sender unit for any given gauge is specific to the gauge, not the engine...marine engines complicate things a little by adding the dual station option that wouldn't exist in autos.

    Finding a replacement will require the details from the gauge...many times, the make is sufficient; others it requires a a year or a model number...any good auto shop specializing in gauges should be able to locate a sender for you.

    The ohm value for a sender should be measured disconnected from the gauge as the gauge will change the reading...The numbers you posted suggest a "normal" US standard sender but the values fall off a little fast - could have been just the measurements...

    As far as the replacement, you can try a sierra or teleflex replacement or go to radio shack and buy a few resistors to characterize the gauge with.

  4. #4

    Default Re: Fireball 225 Temp Sender for '58 Century?

    Thank you for the info, Makomark.

    The gauge case markings only indicate "6V". The sender has absolutely no markings at all.

    The resistance values were recorded with the engine running and wire to the gauge unhooked. The temperature was taken at each step by briefly touching the gauge wire to the sender terminal and reading the gauge itself.

    I'll try those sources and any other that I find for a replacement.

    As an alternative, your concept of re-characterizing the gauge with the use of add-on resistors might be the way to go, possibly allowing the other sender - which has a higher overall resistance, has clear markings on it and can be purchased at auto supply stores - to be used. Thank you for letting me know about that possibility.

    Fritz

  5. #5
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    6,764

    Default Re: Fireball 225 Temp Sender for '58 Century?

    Actually, you characterize the gauge by using resistors in place of the sender units...the quick and dirty check is to apply power to the gauge and go the the sender end of the wire connecting it to the gauge. remove sender wire from sender - gauge falls to MIN value. take sender wire and ground it - gauge flys to MAX value. take 110 ohm resistor and connect one end to the sender wire and ground the other end - gauge should go to mid scale (1/2 way).

    the refinement is to substitute 240 ohms for the "open" test (min value on scale) and 33 ohms for the "short to ground" test...

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