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hooking up relay to turn off another device when turned on

Discussion in 'Electronic Repair' started by [email protected], Jul 18, 2006.

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  1. Guest

    I am trying to hook up a relay to turn off a light when I turn on my
    electric water, keep forgetting, I am sure this is a simple solution,
    Basically my little "IDIOT" light will be on all the time when ignition
    on until I turn on my switch for my fans and electric water pump on
    vehicle, then idiot light will turn off. I know I could hook it up for
    the switch and problem would be solved, but I have a temp sensor which
    turns it off and cools down without ignition on. thanks
  2. Arfa Daily

    Arfa Daily Guest

    I guess that you just need to hook up a 12v ( assuming that it's a 12v
    vehicle system that we're talking here ) SPCO relay's coil between the
    switched feed to your pumps and fan, and vehicle ground. You then need to
    hook an ignition-controlled 12v supply to the normally closed relay contact,
    and one side of a lamp to the moving contact. The other side of the lamp
    goes to vehicle ground. With the ignition on, but the fan / pump switch off,
    current will flow through the lamp via the normally closed relay contacts,
    and the lamp will light. When you switch on the fan / pump switch, the relay
    will be energised at the same time, and the contacts will change over. There
    will no longer be a current path through them and the lamp, and the lamp
    will go out.

  3. If the lamp was hooked across the two switch terminals then it would be
    lit when the switch is open (off) and unlit when the switch is closed,
    the pump and fan would act essentially as the 'common' line as they
    would have far less resistance than the light bulb.

    I am not sure what your reference to the temp sensor means... is it in
    series with the switch and disables the circuit when the unit is hot?

    John :-#)#
    (Please post followups or tech enquires to the newsgroup) John's
    Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 Call
    (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games) "Old pinballers never die, they
    just flip out."
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