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I'm trying to connect an old/possibly broken switch to a light from a 12V battery (very good first question isn't it?). The switch is meant to light Green when ON mode and Red in OFF mode.

The schema (as I traced it) looks like this but actually looks like shown at the bottom

enter image description here

My first question is, is the schema correct? I went several rounds tracing and came up with the same but it looks wrong i.e. when switch is ON there seems to be a short circuit but that obviously can't be right. So I believe the pins should be GROUND, +VE and CONTROL. But this doesn't align with what's printed on the circuit. So which one is correct?

My second question is, how can I wire this to a 4pin relay (to connect to a car battery)? e.g. something like this?

enter image description here enter image description here

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  • \$\begingroup\$ There's no way that's correct, pressing the switch would short out the supply. \$\endgroup\$
    – Hearth
    Commented Jan 24, 2021 at 1:07
  • \$\begingroup\$ Measure the voltage between the 12V+ and 12V- terminals - sometimes those labels are used to mean the + and - terminals of a single 12 volt supply, rather than two 12V supplies relative to Ground/Zero volts. \$\endgroup\$
    – Peter Bennett
    Commented Jan 24, 2021 at 1:12
  • \$\begingroup\$ Yes, it looks incorrect the way terminals are marked - the only sensible explanation is +/-12v indicates poles of 12v supply. If that's the case still, both lights should be ON regardless of the switch isn't it? So my guess is my schema trace is wrong. So what's the actual schema.. it looks pretty simple and sort of puzzles me.. \$\endgroup\$
    – ubi
    Commented Jan 24, 2021 at 1:26
  • \$\begingroup\$ If you think you've drawn up the schematic wrong, have a try at drawing it up again. Start with one wire, draw everything it's connected to, then repeat with other wires and components. \$\endgroup\$
    – K H
    Commented Jan 25, 2021 at 7:45
  • \$\begingroup\$ the schematic looks fine to me, the labels are a little confusing, but note it says "12V+" not "+12V" there is a difference. \$\endgroup\$
    – Jasen Слава Україні
    Commented Jan 25, 2021 at 19:12

2 Answers 2

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schematic

simulate this circuit – Schematic created using CircuitLab

enter image description here

Proof by sim

Updated Request : Solution —- If you can modify the wiring to look like this, it will work for the relay.

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  • \$\begingroup\$ there's no way that that matches the circuit board. \$\endgroup\$
    – Jasen Слава Україні
    Commented Jan 25, 2021 at 1:50
  • \$\begingroup\$ the question is not how to make one, the question is how to use the circuit he has., \$\endgroup\$
    – Jasen Слава Україні
    Commented Jan 25, 2021 at 19:09
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    \$\begingroup\$ Thanks this is a great answer @TonyStewartSunnyskyguyEE75 I'll try your updated circuit (with diode). The 12v comes from car battery - and don't want to keep the RED ON when ignition is OFF. So I got to take the 12v from a source that's switched by car ignition? \$\endgroup\$
    – ubi
    Commented Jan 26, 2021 at 1:50
  • \$\begingroup\$ Yes but the switch must to latch if want relay to stay on \$\endgroup\$
    – D.A.S.
    Commented Jan 26, 2021 at 3:41
  • \$\begingroup\$ it's not -12V it's 12V- which is entirely different. \$\endgroup\$
    – Jasen Слава Україні
    Commented Jan 26, 2021 at 5:28
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schematic

simulate this circuit – Schematic created using CircuitLab

your ?? terminal connects to the lamp. (or to the relay coil in your planned modified version)

+ is your positive supply terminal (blue wire) - is your negative supply terminal (black wire) it also connects to the lamp (or relay coil)

the lamp (or relay) must be present for correct operation.

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  • \$\begingroup\$ This does not reflect the PCB layout \$\endgroup\$
    – D.A.S.
    Commented Jan 25, 2021 at 0:56
  • \$\begingroup\$ I was working off the Falstad schematic, how is the layout different? \$\endgroup\$
    – Jasen Слава Україні
    Commented Jan 25, 2021 at 1:34
  • \$\begingroup\$ apart from the resistors (now corrected to 4k7) \$\endgroup\$
    – Jasen Слава Україні
    Commented Jan 25, 2021 at 1:41

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