Why the negative cable?
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Senior User
Joined: Mar 2004
Posts: 155
Likes: 0
Why the negative cable?
People and Articles always say "Disconnect the Negative Cable" from the battery...
Why? What's wrong with disconnecting the positive?
All you're doing is removing electrical power from the components...
Since I am not using my '95, and after what happened to my first one (see gallery), I always disconnect the battery...
- Stranger
Why? What's wrong with disconnecting the positive?
All you're doing is removing electrical power from the components...
Since I am not using my '95, and after what happened to my first one (see gallery), I always disconnect the battery...
- Stranger
Elder User
Joined: Apr 2004
Posts: 970
Likes: 3
When you disconnect the positive there is always the chance that you slip with the wrench reinstalling it and you get burned or the diodes in the alternator take a hit
and shortout. It is the safe way to do it. Also when working on or around electrical
stuff take off your rings, no better way to get a nasty burn, or lose a finger
and shortout. It is the safe way to do it. Also when working on or around electrical
stuff take off your rings, no better way to get a nasty burn, or lose a finger
Lead Driver
Joined: Sep 2002
Posts: 9,182
Likes: 12
From: Gateway to the West
The simple truth of the matter is that if there is no load on the battery when you remove the cable it really makes no difference. However, since there is more than likely a problem of some sort that is necessitating the removal of battery power, its safer to remove the NEG for the reasons stated above. Electricity doens't really care where you stop it it just tends to "argue" more when you mess with the POS side of the circuit.
Something to keep in mind regardless of which cable you disconnect, if YOU or any part of you complete a circuit that has ANY load on it whatsoever, YOU will conduct that electricity... sometimes painfully. In other words if you decide to reconnect the NEG cable and the underhood lamp is connected, don't grab the NEG cable AND the NEG battery post at the same time with opposite hands. You WILL feel it even though its the NEG side of the circuit. Electricity just isn't at all discriminating about the path it takes to ground.
Something to keep in mind regardless of which cable you disconnect, if YOU or any part of you complete a circuit that has ANY load on it whatsoever, YOU will conduct that electricity... sometimes painfully. In other words if you decide to reconnect the NEG cable and the underhood lamp is connected, don't grab the NEG cable AND the NEG battery post at the same time with opposite hands. You WILL feel it even though its the NEG side of the circuit. Electricity just isn't at all discriminating about the path it takes to ground.
Post Fiend
Joined: Mar 2002
Posts: 19,402
Likes: 38
From: Bonita Springs FL
It actually DOES matter. 
The big reason is that these trucks are negative ground, meaning that every metal body part, including the frame, motor, and all body panels, are part of the electrical circuit to the battery. When you touch the door handle to open the door, it's the same as touching the negative battery post.
So if you remove the negative battery cable first, you're not doing anything different than opening the hood from an electrical standpoint.
Now, if you were to disconnect the positive terminal first, there is a lot more opportunity to get a nasty shock. Grab a hold of the frame and touch positive post and you'll get a surprise. You can do the positive cable first, but you have to be VERY careful. You don't have to be nearly as careful the other way around.
Once the negative cable is disconnected, you're eliminating the possibility of shocking yourself, unless you're a complete klutz, in which case you shouldn't touch the battery at all.
The big reason is that these trucks are negative ground, meaning that every metal body part, including the frame, motor, and all body panels, are part of the electrical circuit to the battery. When you touch the door handle to open the door, it's the same as touching the negative battery post.
So if you remove the negative battery cable first, you're not doing anything different than opening the hood from an electrical standpoint.
Now, if you were to disconnect the positive terminal first, there is a lot more opportunity to get a nasty shock. Grab a hold of the frame and touch positive post and you'll get a surprise.
You can do the positive cable first, but you have to be VERY careful. You don't have to be nearly as careful the other way around.Once the negative cable is disconnected, you're eliminating the possibility of shocking yourself, unless you're a complete klutz, in which case you shouldn't touch the battery at all.
Lead Driver
Joined: Sep 2002
Posts: 9,182
Likes: 12
From: Gateway to the West
Yes, true, but the fact of the matter is that electricity will still stop flowing no matter which cable you disconnect. My point was simply that other than the safety issue, the effect of removing a battery cable, be it POS or NEG will be the same. And once the positive terminal is no longer in contact with the positive post, the only shock hazzard is between the positive post of the battery and the frame. Obviously, as stated above, you have to touch the positive cable to remove it from the post. Thats where the danger lies. Once the positive cable is disconnected, there is no more electricity running through it.
Lead Driver
Joined: Sep 2002
Posts: 9,182
Likes: 12
From: Gateway to the West
Its very possible to get a 12 volt shock. Voltage isn't what kicks you in the @#$. Amperage does that. a battery capable of generating 600-800 CCA @ 14VDC will kick hard! Whereas the model train transformer that puts out close to 15VDC @ 3-5 amps will not even be able to get one of your headlamps to glow.
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Post Fiend
Joined: Mar 2002
Posts: 19,402
Likes: 38
From: Bonita Springs FL
You absolutely CAN get a 12v shock from a car battery. Lick your fingers and then grab both battery terminals. When you wake up a few hours later, you'll likely change your tune.
greystreak - I think we're on the same page. I was just explaining it a different way, that's all.
greystreak - I think we're on the same page. I was just explaining it a different way, that's all.
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Cargo Master
Joined: Nov 2003
Posts: 2,000
Likes: 38
From: North Dakota
Let me tell you! There is a such thing as a 12v shock! I had a cresent wrench and was disconecting the positive when I tapped the body. Melted the wrench to the post and singed the skin off both of my fingers! Hurt like crap!
Freshman User
Joined: May 2004
Posts: 31
Likes: 0
From: Richfield, Utah
Here is my two cents
I prefer to disconnect the battery completely.
Disconnect negative terminal FIRST and positive SECOND. That way, you wont get burnt like Kameronth did by accidentally touching any metal surface in the engine compartment.
To reconnect, alway do the positve FIRST, then the negative, exactly reverse order, for the same reasons as before.
Think about it, it works and you dont get hurt or risk damaging anything.
I repair TV's and have been hit by 30,000 volts of DC, stopped my heart.
I prefer to disconnect the battery completely.
Disconnect negative terminal FIRST and positive SECOND. That way, you wont get burnt like Kameronth did by accidentally touching any metal surface in the engine compartment.
To reconnect, alway do the positve FIRST, then the negative, exactly reverse order, for the same reasons as before.
Think about it, it works and you dont get hurt or risk damaging anything.
I repair TV's and have been hit by 30,000 volts of DC, stopped my heart.
Post Fiend
Joined: Jan 2004
Posts: 6,610
Likes: 2
From: Northwest, Arkansas
Ahh but no one has responded with the main reason to disconnect the negative first. The main reason lies in the fact that if you remove the positive first there is a greater and probable chance of arcing to the post as you remove it. Though this may be Small there is the chance that it could cause the battery gasses to explode. A battery blowing up in your face is not fun nor pretty so be careful. On newer vehicles it not only has a safety issue as already stated but it could also cause severe damage to the newer electronics on the vehicle.