[DaleM]

There has to be a difference, but why do instructions involving wiring always say to disconnect the negative (-) cable and don't say to disconnect the positive (+) cable? Wouldn't disconnecting the negative still leave a path to ground if you accidentally touched a hot wire (sic) to ground? On the other hand, disconnecting the positive cable should remove all power from any wires in the system - even those that are always hot as opposed to just ignition hot.

What am I missing here?

 

[68KMENO]

think circle 0 all things electric make a circuit or like I said a circle ... ground is the same as postive only the other side of the circle... OK now think what would happen if you touched ground when removing the POSTIVE side .... dead short !! now what would happen if you touched ground while removing ground ... NOTHING see why its safier to remove the ground wire now ??? this is a overly simple example but ... I'm not going to explain Ohm's law here

 

[DaleM]

I guess that makes sense when removing the battery cable itself...but doesn't that still leave the possibiity of accidentally shorting (or grounding) any wires when working on the car with the positive cable still connected?

 

[pmullaly]

But Dale, while your removing the Battery cable(*lets say the POS cable) to repair whatever it is. What would happen if your wrench touches the Fender and pos post at the same time?
Now doing the same repair you first disconnect the Neg side of the battery first... your wrench slips and you make contact with the Neg post and the fender == nothing happens -no sparks.
once you've removed the path back to the Neg post of the battery nothing in the car is going to be hot(except the battery)

 

[Barista]

So....it sounds like it's best to remove both cables, just do the negative first. Right?

 

[MalibuJerry350]

Originally posted by Dale McIntosh:
I guess that makes sense when removing the battery cable itself...but doesn't that still leave the possibiity of accidentally shorting (or grounding) any wires when working on the car with the positive cable still connected?

No, the current would have no return path with the negative cable disconnected.

 

[Dean]

Originally posted by Barista:
So....it sounds like it's best to remove both cables, just do the negative first. Right?

to remove the battery ,,, yes

otherwise, like Jerry said only the negative needs to be removed

 

[DaleM]

I use a side terminal battery and my positive cable is easier to get the wires off and on than the negative cable is due to hoses, other wiring and such plus I have a few "always hot" connections off the positive side.

I was just curious if there was some real "electical" reason for removing the negative side instead of the positive side. I guess I feel more confident removing the positive cable. That way I know there's no juice running anywhere through the car.

 

[John_Muha]

Only because you regard the positive as more important on a negative ground car. In reality the battery nor the circuit doen't care. Either electron theory or conventional current, it all goes around.

 

[MalibuJerry350]

AGAIN, as John said, the positive cable is more important to address in a negative ground vehicle. Lets say you're wrenching on the positive battery cable and the wrench hits the fender, a grounded bracket, radiator support. BANG!! A shower of sparks and possibly a welded wrench to whatever component it came in contact with! NOW, by removing the NEGATIVE cable first, there is NO chance of that happening. THAT'S the logic behind removing the negative cable first.....top OR side terminal battery. Ask my son how he found out the hard way while removing the positive cable first on his '86 Olds (side terminal)! Instant battery destruction! AND, a fresh change of underwear! After all, what does Dad know!?!

 

[John_Muha]

Yeah Jerry, sometimes live and learn. Mine was so smart one time also. Instead of removing the negative cable from the battery, like I told him, he unscrewed the cable off the alternator bracket. It was so much easier to remove. This doesn't remove the ground connection from the battery to the frame. So in changing out the alternator he goes and pops the new one. That one was a newly rebuilt one that I had sitting around that was costing him nothing. Now he needed to go out and buy one.

 

[68KMENO]

kids....... you got to LOVE em.. Mine decided that he had a charging problem & would check it by removing the battery cable while car was running !!! the resulting power spike took out the unilite ing.. the radio ... & the radar detector....... anyone intersted in a good used kid ????

 

[d1_bradley]

Its just a safety thing. If you slip and touch the wrench to the body while removing the negative cable, nothing happens (NO SPARK) Do the same with the positive cable and it will SPARK, and its right next to the hydrogen gas created by the battery acid. Can you say BOOM! Same when installing a battery or jumper cables, hook the positive up first, then the negative. And with jumper cables make the last connection AWAY from the battery, like an engine bracket. Much safer.

 

[Chevello]

Or, as my old boss told a new kid at the resto shop once, "Because you can do THIS" (and laid a wrench across from the negative terminal to the fender)
"But you CAN'T do THIS! Oh [email protected]**#*&(*&^$*&% somebody get me a damn hammer, the wrench welded itself to the terminal!!!!!!"

Apparently he was so into being cool, he didn't realize that the negative cable was still on.

I've got a couple of special stories about that guy.

K

 

[DaleM]

I totally agree that one must be careful when removing the positive cable when the negative is still connected...no argument there.

But let me get this straight in my head. Negative cable has been removed from the battery, positive cable is still connected. Positive cable still goes to the solenoid, a 10ga wire goes to a junction block and, in my case, there's a large (probably 0 or 00) gauge cable going to one stereo amp, one 10ga wire going to my Painless Cirkit box, and two smaller wires going to feed the fuel injection harness. You're saying that if the negative is removed and the positive is not there is NO possiblity of grounding any (always hot) wire or connection accidentally? Or more simply, with the negative cable off I can lay a wrench from the positive cable to any ground point and it won't weld itself? I guess in my mind I just see all these little electrons running from the battery along the wiring system looking for a ground. Bottom line, the only reason for removing the negative instead of the positive is step one, removing A cable; a slip removing the negative - no problem, a slip removing the positive - problem.

I guess that's a problem we "electrically challenged" guys have.

 

[Joe Y]

I just had a "great" expierence with my daily beater (and man it is beat). Battery died cause stupid me left the parking lights on at work. Battery was also 8 years old. Battery decided the plates inside would rather like to fuse together. Found out after I try and get a jump. Why are there tons of sparks comming from the posative? Short in my jumper cables? Get a different set of cables, still happens. So I ended up jumping it at the cable, covering the posative cable with electrical tape I keep in the glove box and drove it 90 miles home on the alternator.

 

[MalibuJerry350]

Originally posted by Dale McIntosh:
Or more simply, with the negative cable off I can lay a wrench from the positive cable to any ground point and it won't weld itself? I guess in my mind I just see all these little electrons running from the battery along the wiring system looking for a ground. Bottom line, the only reason for removing the negative instead of the positive is step one, removing A cable; a slip removing the negative - no problem, a slip removing the positive - problem.

I guess that's a problem we "electrically challenged" guys have.

Yep! No problem! The electrons can't return to the battery, so everyone's happy!