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Old 04-07-2004, 07:16 PM   #1
DougSilver
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Default Disconnect negative battery terminal--really necessary

I have been removing and inspecting the IAC valve on my 95 and have ordered a new one to install. I realize the service manual says to first disconnect the negative battery terminal and I neglected to do this. I figured if the key is not turned on, what is the risk? Then I noticed that the service manual states to disconnect the negative terminal when doing almost anything on the car.

Is the main reason for this to reduce the chance of shorting something when using tools inside the engine compartment or is there some other reason? I assume that if you are careful and keep the key turned off, it seems overkill to have to remove the battery terminal just to change a part.

Doug
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Old 04-07-2004, 07:22 PM   #2
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Default Re: Disconnect negative battery terminal--really necessary (DougSilver)

Not sure, but I learned that if you remove the ditigal dash out of the car( my 84) it will KILL the battery overnight. I mean kill. 1.35 volts left.

Just something to think about.
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Old 04-07-2004, 07:31 PM   #3
ZylaRace
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Default Re: Disconnect negative battery terminal--really necessary (DougSilver)

Mainly put in by the lawyers. Big Brother know's what is good for you,... just ask him.

Basic safety stuff.
As far as IAC,.... you won't harm anything.

Make sure the IAC is fully retracted before you install it. (Else you risk breaking it.)
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Old 04-07-2004, 07:57 PM   #4
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Default Re: Disconnect negative battery terminal--really necessary (DougSilver)

:iagree:
Though the ECM is sensitive to static discharge you should be ok, just keep fingers away from the cable socket.

I only pull the battery lead when it would be dangerous to me, like when changing spark plugs, working on the front, etc or necessary to change an electrical component like the alt or starter.
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Old 04-07-2004, 08:09 PM   #5
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Default Re: Disconnect negative battery terminal--really necessary (DougSilver)

The ECM and probably a bunch of things on your '95, that I don't even know about, remain "live" with the ignition off. I almost routinely disconnect the battery when I open the hood. Interestingly, changing plugs, is one thing, I don't disconnect the battery for.

RACE ON!!!
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Old 04-07-2004, 09:21 PM   #6
art1217
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Default Re: Disconnect negative battery terminal--really necessary (DougSilver)

In the 93, the CCM stays powered with the ignition off. The unit goes into sleep mode until the some action is detetected and then wakes up. If the CCM did not sleep, it would drain the battery.
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Old 04-07-2004, 09:29 PM   #7
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Default Re: Disconnect negative battery terminal--really necessary (CFI-EFI)

But even if there is some charge in the PCM/ECM, I can't believe there would be any harm in disconnecting the IAC and reconnecting it as long as the key was off. Am I wrong?
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Old 04-08-2004, 01:15 PM   #8
MrNuke
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Default Re: Disconnect negative battery terminal--really necessary (HeeHaw89)

I can safely say I've never disconnected the battery in my car for anything other than when I had to change the battery itself, or when I was doing major work (heads/full intake). I have never had anything fry either. Probably more of a 'safety' thing from GM to cover their butts from stupid law-suits..

Also to someone who posted about the battery wearing down when the lcd is disconnected, I don't think that is right. You might have a short somewhere there. I had mine off for almost 2 weeks when I had it rebuilt years ago, and the battery never wore down.
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Old 04-08-2004, 01:34 PM   #9
swifty
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Default Re: Disconnect negative battery terminal--really necessary (DougSilver)

I thought about doing it it just because you never know, but fretted about having to re-program the radio stations and clock. When I noticed it was suggested for literally EVERY procedure I decided to use common sense and just disconnect when there is a higher risk of damaging an electronic component - or the operator. So far, so good.
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Old 04-08-2004, 02:20 PM   #10
DougSilver
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Default Re: Disconnect negative battery terminal--really necessary (HeeHaw89)

Thanks for all the replies. I believe these confirm my own thoughts that while it is undoubtedly safest to disconnect the battery, it is not absolutely necessary if you take adequate care not to short something. I also suspect that even the dealership doesn't bother doing this as I have never had to reprogram my radio after picking up the car (then again, they may have disconnected the battery but installed some gizmo in the cigarette ligher to maintain radio settings, etc.)
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Old 04-08-2004, 05:44 PM   #11
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Default Re: Disconnect negative battery terminal--really necessary (HeeHaw89)

i read this thread yesterday and it reminded me of this weekend...the book says to disconnect the battery to change the o2 sensors and naturally i didnt , when taking off the passenger side one on my 94, my wrench hit the live wire on the starter and sparked, the wrench fell out of my hand and hit me in the forehead :crazy:

i guess im gonna start disconnecting the neg. side of the battery when i change my windshield wipers from now on :)
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Old 04-08-2004, 09:57 PM   #12
HeeHaw89
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Default Re: Disconnect negative battery terminal--really necessary (DougSilver)

I never unhook the battery except when pulling the chip. Never had a single problem.
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Old 04-08-2004, 10:35 PM   #13
George Dickel
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Default Re: Disconnect negative battery terminal--really necessary (DougSilver)

It's cheap insurance. Takes only a couple minutes to pull the cable off vs shorting out a circuit and frying a couple modules, sensors and burning up 35 feet of wire. I seem to have a knack for hitting the wrong wire at the right time.
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Old 04-08-2004, 10:39 PM   #14
HeeHaw89
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Default Re: Disconnect negative battery terminal--really necessary (George Dickel)

Quote:
It's cheap insurance. Takes only a couple minutes to pull the cable off vs shorting out a circuit and frying a couple modules, sensors and burning up 35 feet of wire. I seem to have a knack for hitting the wrong wire at the right time.
:iagree:
I should start doing this, you never know.


[Modified by HeeHaw89, 10:39 PM 4/8/2004]
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Old 04-08-2004, 10:39 PM
 
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