Which cable to disconnect
Thread Starter
Veteran
Joined: Jan 2000
Posts: 2,082
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From: Louisville KY
Which cable to disconnect
When you're getting ready to work on the car which battery cable should you disconnect? Does it matter? Is their a safety issue in regards to the car or my own personal well being?
Thanks
Thanks
Melting Slicks
Joined: Dec 2004
Posts: 2,677
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From: I have to return some videotapes
I'm glad you asked this question ROCKnROLL, as I have been wondering the same. I've always disconnected the positive first, then reconnected the ground first, but I'm not sure that's correct or where I learned it.
On a related note, when dis/reconnecting the cables, they make intermittent contact with the terminals as I'm tightening, sending short bursts of power through the electrical system. I feel like this cannot be good for various electrical components, and I'm pretty sure it led to my recent column lock nightmare. Do you know a better way, or am I needlessly obsessing? TIA
On a related note, when dis/reconnecting the cables, they make intermittent contact with the terminals as I'm tightening, sending short bursts of power through the electrical system. I feel like this cannot be good for various electrical components, and I'm pretty sure it led to my recent column lock nightmare. Do you know a better way, or am I needlessly obsessing? TIA
Instructor
Joined: Sep 2005
Posts: 140
Likes: 13
From: Harrisburg PA
You should always disconnect the negative cable first. The reason for this is if you touch your wrench to ground when taking off the positive cable off first it will short causing sparking or possible explosion. If the negative cable is disconnected first the circuit is not completed when taking off the positive cable.
Racer
Joined: Oct 2006
Posts: 445
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From: State of Perplexity California
Originally Posted by kawasaki eric
You should always disconnect the negative cable first. The reason for this is if you touch your wrench to ground when taking off the positive cable off first it will short causing sparking or possible explosion.
You've not had a truly exciting day until you've seen your wrench short to ground, making a big spark and instantly welding itself to the rest of the car. The next few seconds, things get really interesting...
Melting Slicks
Joined: Jul 2006
Posts: 2,332
Likes: 31
From: Silver Spring MD
battery disconnect
NEGATIVE FIRST for reasons given ie shorting out against metal frame etc.
Does anyone remember the old GM DELCO COMMERCIAL for batteries?
NEGATIVE
&
POSITIVE
& RUBBER SEPERATORS.
DELCO POWER
WE'ER GONNA MAKE POWER
Does anyone remember the old GM DELCO COMMERCIAL for batteries?
NEGATIVE
&
POSITIVE
& RUBBER SEPERATORS.
DELCO POWER
WE'ER GONNA MAKE POWER
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Team Owner
Joined: Jul 2006
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From: Kannapolis NC
I learned the hard way in the 60's. I tried disconnecting the positive first on a 65 Vette and had on my high school class ring. With the wrench on the positive terminal and in the palm of my hand, I turned the bolt and my ring touched the engine block. Not only did it melt my gold ring, it blistered a new ring all around my finger. I don't do it that way now.
Drifting
Joined: Oct 2005
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From: Terrell North Carolina
Always negative First. This really became important with the start of computer cars. The idea is to remove negative first and positive last. The reasoning for this is to prevent a voltage spike that can harm the computers. There have been voltage spikes that have been measured over a 100 volts, when that happens, good by computers. When reinstalling the cables, Positive First Negative Last. When you reinstall in this order, voltage spike goes to ground.
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Originally Posted by BELVIN20
Always negative First. This really became important with the start of computer cars. The idea is to remove negative first and positive last. The reasoning for this is to prevent a voltage spike that can harm the computers. There have been voltage spikes that have been measured over a 100 volts, when that happens, good by computers. When reinstalling the cables, Positive First Negative Last. When you reinstall in this order, voltage spike goes to ground.
That's the way to do it.
Le Mans Master
Joined: Aug 2003
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From: American Canyon Lethal Injection
Originally Posted by BELVIN20
Always negative First. This really became important with the start of computer cars. The idea is to remove negative first and positive last. The reasoning for this is to prevent a voltage spike that can harm the computers. There have been voltage spikes that have been measured over a 100 volts, when that happens, good by computers. When reinstalling the cables, Positive First Negative Last. When you reinstall in this order, voltage spike goes to ground.
This is the correct way.
Safety Car
Joined: Jul 2005
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From: Omaha Nebraska
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Originally Posted by BELVIN20
Always negative First. This really became important with the start of computer cars. The idea is to remove negative first and positive last. The reasoning for this is to prevent a voltage spike that can harm the computers. There have been voltage spikes that have been measured over a 100 volts, when that happens, good by computers. When reinstalling the cables, Positive First Negative Last. When you reinstall in this order, voltage spike goes to ground.
Yup, this is what I've always been told. 
Race Director
Joined: Jan 2006
Posts: 10,554
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From: Not on either liberal coast.
...along the same lines, always remove any jewelry like watches/rings or body piercings if you don't disconnect the battery.
It's never happened to me...however, I've seen images of people who failed to do this and not only welded their favorite wedding ring to their car, but got really nasty burns as well.
It's never happened to me...however, I've seen images of people who failed to do this and not only welded their favorite wedding ring to their car, but got really nasty burns as well.