Rep Power: 786

I am just wondering if the ground wire for the decks on our cars is switched on and off by the ignition?

That sounds crazy, but the reason I ask is that I was wiring an LED scanner in earlier, and it had a 3 wire hookup (black [neg], red [pos], yellow [switched]). You can tell by that color configuration that I spliced the yellow into my deck's red wire and red into the yellow.

Wierd thing is that when I connected black to black which is what should be done, the scanner turned off... when I removed it, it turned on.

I'll be god damned if I know wtf is going on, but it almost seemed liek the ground wire is switched. My backup proof for this is that it doesn't remember the pattern that I left it on once I turn the ignition on, removing the switched 12v ground and wiping the scanners memory.

Anyway, if you can make sense of my nonsensical ranting, tell me what you think and try and explain WHY exactly I am experiencing this phenomena.

P.S. I did not come up with this theory until everything was back together and I was not about to rip it back apart and test to see if I was right.

 
Rep Power: 0

Could be like the ground on some HU's. On some if you forget to connect the ground the HU will still work. It grounds itself through the antenna hookup. However I'm sure it isn't good for the HU at all and will probably burn something out ASAP.

 
Rep Power: 786

It's not the fact that it works without the ground hooked up, I understand how that works, the switched 12v source becomes ground when the vehicle shuts off, effectively powering up anything in it's path given a constant 12v source.

The question is why does it not work ONLY WHEN ground is hooked up?

 
Rep Power: 329

the "switched" wire (or ignition) does not become a ground when the car is off. it simply creates an open circuit, thus there is no current flow.

i think that yellow is actualy the constant 12V or direct battery connection. red is then the ignition wire. thats how my harness is

battery generally connects in the middle of a 3 input switch, if that helps any. because LED's only turn on one way, reversing polarity of a logic circuit can give you some pretty crazy results, but i doubt you'd damage anything

you are right about that being nonsensical. i feel dumber everytime i try to read that.