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#128515 - 05/14/03 09:21 AM car runs with no negative?
james S Offline
Member

Registered: 05/13/03
Posts: 102
Loc: West England
when washing my car last i got bored and decided to see what would happen if i disconnected the negative side of the battery.When dist the car continued to run with no change whatsoever?

[This message has been edited by james S (edited 05-27-2003).]

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#128516 - 05/14/03 09:34 AM Re: car runs with no negative?
C-H Offline


Member

Registered: 09/17/02
Posts: 1508
Loc: Stockholm, Sweden
If it started without battery, I have no suggestion, unless you have a very, very expensive car with two batteries.

If it was already running, of course it continued to run. The generator supplied the power. There is a voltage regulator on the generator that keeps the voltage to about 14V.

Running the car without battery is considered emergency operation and the electric system could be damaged.

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#128517 - 05/14/03 09:48 AM Re: car runs with no negative?
Bill Addiss Offline
Member

Registered: 10/07/00
Posts: 4196
Loc: NY, USA
Brings back memories. My first car was a '61 Rambler American. It had a stickshift and a bad battery (I'm thinking at times no battery at all ??). To get it started I'd let it roll out the driveway and down the street then pop the clutch, and I'd always have to remember to park it on a hill wherever I went.

Ah, the good ol' days...


Bill

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#128518 - 05/14/03 10:35 AM Re: car runs with no negative?
james S Offline
Member

Registered: 05/13/03
Posts: 102
Loc: West England
SORRY, SILLY SILLY QUESTION!!!!!!!!!!!!!!!

AT LEAST OUR BILL COULD SIT BACK AND RECALL THE GOOD OLD DAYS!

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#128519 - 05/15/03 07:04 AM Re: car runs with no negative?
George Corron Offline
Member

Registered: 05/16/01
Posts: 728
Loc: Lorton, Va USA
Actually, if you suspect you have a bad alternator, with the car running, lift one of the battery terminals. If it quits, the alternator has no output, but if all is good, the car will keep running just fine, but without a load to discharge into, the alternator will eventually be damaged.

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#128520 - 05/17/03 08:29 PM Re: car runs with no negative?
frenchelectrican Offline


Member

Registered: 02/06/03
Posts: 938
Loc: Wi/ Paris France { France for ...
yeah that bring me alot of memories with my old diesel truck few time the battery actally quit on me and can push start my diesel ( it is a old detort disesl [ 3-92TA]) and it have dual alternators both 12 and 24 volts and when the 24 fail i useally push start but dont ask me if someone want to jump start i have 2 jumper ports one marked 12 v and the second one is marked 24 it is really clear words and my engine have gear driven altenrors . and my heater fan is wired for 24 volts it stay running all the time during engine running time and the headlight are wired also on 24 but trailer connetions have both 12 and 24 volts there and i dont use the voltage conveter i just use relay for functions . most of my trucks have 24 system there and therefore if regulator go bad it will shut down anyway

merci marc
_________________________
Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)


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#128521 - 05/19/03 06:49 AM Re: car runs with no negative?
C-H Offline


Member

Registered: 09/17/02
Posts: 1508
Loc: Stockholm, Sweden
Quote:

Actually, if you suspect you have a bad alternator, with the car running, lift one of the battery terminals.


I once bought a car from a guy who had disconnected the warning light, as he knew the alternator wasn't working. He didn't tell me of course. Care to guess what happens if you drive a car without alternator?

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#128522 - 10/27/04 02:27 PM Re: car runs with no negative?
SimonUK Offline
Member

Registered: 10/15/04
Posts: 50
Loc: Ayrshire, Scotland, UK.
If you've ever been near a car battery when it explodes then you would know never to disconnect the battery when the engine is running.

If a battery or alternator is suspect then there is a very real chance of the battery gassing.

The spark caused by disconnecting the battery lead is enough to ignite the hydrogen gas and BOOOOOMMMM!!!!!!!

I was once on a wee grey Fergie tractor where the battery (in this case the battery was only 3 weeks old) is right next to your seat. I had just looked up from the battery as I was cranking the engine when it exploded covering me in battery acid and plastic from the case.

You've never seen anyone dismount from a tractor and run 80yds into a river as fast in your lives. Still didn't stop my jeans from disintegrating from the acid.

The same rule applies to jumper cables. Connect positive to positive first then connect negative to an engine mounting or a lifting eye on the engine to be started. Once the engine is running remove the grounded (car body negative) clip first.

You must have noticed the size of the sparks when you connect jumper cables. by making the final connection and first disconnect on the engine itself you are taking the sparks away from the vicinity of the battery.

You only have one pair of eyes, hands, arms and one head.

Be safe,

Simon.

PS how many of you have seen a brand new car on show in a shopping mall then looked under the hood only to find the positive lead is disconnected. Only takes a small slip with the spanner and you've melted through some brake lines or even worse fuel lines and....

....well need I say more.

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#128523 - 10/29/04 05:25 AM Re: car runs with no negative?
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
I think Simon makes a very valid point: If the generator has been overcharging, then there could have been a lot of gassing taking place.

Remember too that hydrogren is lighter than air, so with the hood closed the gas will have accumulated in the engine compartment rather than sinking and dispersing out the bottom.

Quote:
Only takes a small slip with the spanner and you've melted through some brake lines or even worse fuel lines and...

Yep, always disconnect the negative first and reconnect it last. Unless it's a vintage car which is positive chassis!

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#128524 - 01/17/05 07:32 PM Re: car runs with no negative?
cpalm1 Offline
Member

Registered: 01/06/04
Posts: 62
never disconnect the battery while the engine is running. aside from the danger of a battery explosion, there is a much larger possibility that you will damage a computer or other electronic part. the battery acts as a buffer and absorbs voltage spikes and and provides extra power when the alternator can't keep up. with the dozens of computers in todays vehicle's, you could cause a couple thousand dollars of damage in just a few seconds.

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