12 volt systems....which is ground?

[87Rockwood]

Originally Posted by Sundancer268

The Dome light in most cars are wired hot to the light and ground through the switches. This makes it easy to use a self grounding switch in the door jams on the older vehicles. The Parking Brake warning light was also wired this way in several Plymouth's and Fords as well as my IHC Scout II. A lot of the newer cars use the ground wire for computer switches also.

Been there, done that. He is just stubborn and does not believe...

[randco]

Originally Posted by Sundancer268

The Dome light in most cars are wired hot to the light and ground through the switches. This makes it easy to use a self grounding switch in the door jams on the older vehicles. The Parking Brake warning light was also wired this way in several Plymouth's and Fords as well as my IHC Scout II. A lot of the newer cars use the ground wire for computer switches also.

Thanks for the reply. I have looked up a dome light wiring diagram on the internet. It is exactly as described by you and others in the thread. I never knew they wired vehicles like this.

[Dr4Film]

Originally Posted by randco

I an interested, can you name a few? Not something like a "kill switch" that is a "short to ground".

Monaco uses some switches where the ground is in series to the switch and then others they use the hot. No rhyme or reason for which way when.

Monaco also decided to use the ground wire to activate brake lights. Sure made it more difficult to wire in a Prodigy Brake Controller. Had to install a separate relay to get a 12 VDC positive brake signal for the brake controller.

So never say never.

Dr4Film ----- Richard

[randco]

Originally Posted by 87Rockwood

Been there, done that. He is just stubborn and does not believe...

Nah, I am not stubborn. I just don't take things said or posted on these forums as gospel. On the contrary, I do believe. I saw a wiring diagram and am satisfied.

[mahon1993]

Originally Posted by garym114

Use a multimeter. It is right every time.

One of the old time tricks if you don't have a volt meter and you're in a pinch to find out which is the + is to stick both wires in a cut open potato. The + wire will foam. Who needs a volt meter anyway!!
Greg

[randco]

Originally Posted by Dr4Film

So never say never.Dr4Film ----- Richard

Richard you are correct. Yes, I was wrong. I stand corrected. I should have never said "never".

Life is about learning new things on a daily basis.

[Dunner]

Alright everybody, leave randco alone; we've beat him up enough.
And to think, this all started on page 1.

[BCooke]

Originally Posted by randco

Nope, the NO Start switch and the NC Stop switch are wired in series to the coil of a relay. The NO set of contacts in the relay are wired in parallel to the NO Start switch.

Well look at a positive pulse input to continual positive latched output with SPST toggle switch to break ground, used in alarm circuits. A diode between the input and the positive output is all that is required to latch the circuit.
Just a FYI.

[randco]

BCooke,

Thanks for the additional information. In my 25+ years of working on packaging machinery with 24 vdc and 120 vac control circuits I had not seen an application where a circuit was switched between the load and ground.

After getting beat up and doing some research I find a lot of applications where the ground is switched. I can see the practical application as it applies to dome lights and various sensors in low voltage dc applications.

I also did some reading on other types of latching relays and was surpised to see the various other types that I was not aware of.

[Dunner]

There is no one smarter than all of us together.

[RustyJC]

Late 2nd generation Dodge Ram trucks used switched ground circuitry to control the headlights, parking lights, etc. This caused all kinds of havoc for accessory manufacturers. See one such bulletin from a snowplow supplier HERE.

Rusty

[BCooke]

Randco, no problem, as long as I keep my head........ I find I continue to learn also. It just takes more to convince me as the years go bye.

[bldrbob]

Some old houses I worked on were switched on the neutral.Made it interesting sometimes.Turn off the switch and grab a wire thinking it was dead.

[JGrosman]

Over head light in car. Lights in lower compartments. Car alarm switch. All have the ground switched.