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Old 09-25-2004, 02:05 PM   #31
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could he of maybe not sense any current because negative current is actually running through that wire instead of positive? I don't know if the Bonneville is the same, but a lot of the turn-on leads on my Riviera are negative. (the horn input is negative, I think my headlight switch output is negative as well.) Not entirely sure though. I'm probably wrong, as usual.


--EDIT I was right, the headlight switch puts out negative current on my car. Is the bonneville the same?
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Old 09-25-2004, 02:15 PM   #32
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Quote:
Originally Posted by Custom88
could he of maybe not sense any current because negative current is actually running through that wire instead of positive? I don't know if the Bonneville is the same, but a lot of the turn-on leads on my Riviera is negative. (the horn input is negative, I think my headlight switch output is negative as well.) Not entirely sure though. I'm probably wrong, as usual.
Somewhere along the line, that negative is turned into a positive though. For example, you are correct that the horn is a negative trigger for the horn relay but the output to the horn is positive. Many newer cars are using negative and even multiplexed (different resistances or data) triggers as inputs to body modules but almost every output is positive.
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Old 09-25-2004, 02:28 PM   #33
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Let'* clarify this a bit. In a closed loop system like a car'* electrical system, it'* not possible to have electrons running both directions when we're not using AC current.

We're not talking about positive and negative here, we're talking about switched POWER or switched GROUND.

Let'* use the horn relay for instance. It always has 12v applied to the coil in the relay, but won't energized until the switched GROUND is applied. At that time, the 12V will travel to the horn and make noises.
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Old 09-28-2004, 05:53 PM   #34
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I got it fixed. When i went out to double check that the bulbs werent burnt and the fuses werent bad, i found out that fuse 14 was poped. I have no idea how i overlooked it, i guess it was because i was in such a rush all of the time, this is the first time that i have really had an opportunity to really get a good chance to work on it. Thanx for all of the sugguestions.
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Old 09-29-2004, 11:23 AM   #35
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Quote:
Originally Posted by randman1
Somewhere along the line, that negative is turned into a positive though. For example, you are correct that the horn is a negative trigger for the horn relay but the output to the horn is positive.
Maybe it would help to think of it in terms of whether the switch for the device is on its supply side or its ground side. A supply-side switch would have a positive output; a ground-side switch would have a negative output.

So "switched-hot," those devices whose switch is on the supply side of the circuit (i.e. you turn on its power), would include most things on the car like its lights, wipers, ignition and so on, but "switched-ground," those devices whose switch is on the ground side (you provide a ground path to activate it), includes the interior lights or the horn relay.

In fact the horn circuit(*) are kind of interesting that way: the horn itself is on a switched-hot circuit, where its switch is the horn relay. However, the relay itself is on a switched-ground circuit: it'* hot at all times, but its contacts close whenever its secondary wire is grounded through the steering wheel, which honks the horn.

Quote:
Many newer cars are using negative and even multiplexed (different resistances or data) triggers as inputs to body modules but almost every output is positive.
Ayup... The oldest one I can remember was the Cadillac Allanté back in, um, 1989 or thereabouts, which I think had one of the first body controllers for the lighting circuits, so that, for example, if a headlamp burned out, the controller would switch on the foglamp on that side to compensate.
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