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  1. #1

    Default Temp sending unit

    I have a 1963 ford 221 interceptor with an eaton outdrive.

    I have a bad temp sending unit and am having a hard time locating a replacement.

    The unit is for a simple indicator light. In this case, the light simply stays on.

    Three trips to the auto shop and I have yet to get a unit that works. The current I am getting sent from these replacements is way too weak for the bulb.

    Any suggestions on a good source? Thoughts on what the problem is here?
    Last edited by copelandg; 11-08-2017 at 09:04 AM. Reason: typos

  2. #2
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    6,799

    Default Re: Temp sending unit

    its not a sending unit if its connected to only a light - its a switch...

    Sending units connect to gauges.....

    The current isn't sourced by the switch; the switch just passes the current from one wire to the other. If the contacts of the switch can't handle the current the bulb needs, I'd bet the easiest solution is to change the bulb to a lower current equivalent (or go high tech and drop in the LED replacement).

    It is also possible that there is one or more connections in the harness between the switch and the bulb that has high resistance and is inducing a voltage drop. If you ground the bulb side of the switch, the bulb should turn on and the rated current should be passing thru the wire. If the bulb is dim, the current thru that wire is probably much less than what the bulb is rated for - and you will have to dig into the harness to find the bad spot or just run a new wire...

    As far as sources, you'll have to be a bit more specific with what you wanna change....

  3. #3

    Default Re: Temp sending unit

    Quote Originally Posted by makomark View Post
    its not a sending unit if its connected to only a light - its a switch...

    Sending units connect to gauges.....

    The current isn't sourced by the switch; the switch just passes the current from one wire to the other. If the contacts of the switch can't handle the current the bulb needs, I'd bet the easiest solution is to change the bulb to a lower current equivalent (or go high tech and drop in the LED replacement).

    It is also possible that there is one or more connections in the harness between the switch and the bulb that has high resistance and is inducing a voltage drop. If you ground the bulb side of the switch, the bulb should turn on and the rated current should be passing thru the wire. If the bulb is dim, the current thru that wire is probably much less than what the bulb is rated for - and you will have to dig into the harness to find the bad spot or just run a new wire...

    As far as sources, you'll have to be a bit more specific with what you wanna change....
    Helpful info.

    I was hoping to get a new switch.

    Just a note that when I insert the old switch, the bulb is brightly lit. If I insert and install a new switch the bulb is very dim. Still I can run new wires to see if there is a problem. Actually may explain the bulb being continuously on in the 1st place.

    Thank again.

  4. #4
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    6,799

    Default Re: Temp sending unit

    if the switch is closed (cold) then it is likely bad...

    if the new switch has the bulb light dimly, then current is flowing thru the bulb - it may be going thru the switch or it could have found another path (wiring issue)....I'd suggest disconnecting the wire, from the switch, when the bulb is glowing dim....if it continues to glow dimly, then there's a wiring issue and the switch is probably ok....

  5. #5
    Join Date
    Dec 2006
    Location
    Chaumont Bay, N.y., USA
    Posts
    5,194

    Default Re: Temp sending unit

    Ayuh,.... It sure sounds like yer tryin' to use a temp sender, rather than an over-heat switch,....

    A temp sender works by varying resistence to ground,....
    A temp switch is either open, or closed to ground,....

    A sender would provide some ground, so the light is dim,....

    A test light or multimeter would clear this up in no time,...
    Any Grease is Better,... Than No grease at All....

  6. #6
    Join Date
    Mar 2009
    Location
    Portland, Oregon,
    Posts
    9,133

    Default Re: Temp sending unit

    Why not install a temperature gauge?
    You'll have much more meaningful information with a gauge than you will with a light that illuminates only during an issue!
    Rick ... aka Ricardo..... AQ series Volvo Penta repair
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP's

    Please... no PMs! Post your questions on the forum.

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