[DML] Re: Jump Start & Computers (was Over revving Auto)

["Tom Niemczewski" <tomciodmc@xxxx>]

Hi,
The surge occurs when you start the car, right at the moment when the engine
starts and you release the key. When you start your car with a healthy
battery the voltage drops to about 9 to 10 volts. When you release the key
it goes back up to about 13.8 (with the help of alternator). This is where
the surge occurs. But since there is just one battery and one alternator,
it's not that bad. The problem is that when you jump the car using juice
from other car, or car starter. When the voltage drops during cranking there
is much more (two batteries and two alternators) trying to get the voltage
back up to 13.8. So, when you release the key you might get a spike going as
high as over 80 volts!!! That is what kills the governor.
Hope that helps.

Tom Niemczewski
tomcio@xxxx
vin 6298

----- Original Message -----
From: Mike Substelny <msubstel@xxxx>
To: <dmcnews@xxxxxxxxxxx>
Sent: Friday, January 28, 2000 5:20 PM
Subject: [DML] Re: Jump Start & Computers (was Over revving Auto)


> Duke said:
>
> > You're correct about the electrical surge. One thing that is
> > really bad for the computer governor is jump starting the car.
>
> Could someone elaborate on this, please? When and how does the surge
> take place?
>
> I assume this means that the tranny computer gets power even while the
> ignition is turned off, and the surge occurrs when the cables make their
> final circuit contact. In this case, jump starting the car will
> suddenly engage the computer . . . something like a battery cutoff
> switch does. Is this really dangerous?
>
> If the computer 'boots up' when you turn the key, then the surge from
> jump starting should be similar to the surge from normal starting. I do
> not understand the danger. How can the computer tell the difference?
>
> I do agree that a battery charger can be deadly to a computer. Most
> chargers do not put out the steady current that a computer wants. They
> put out some sort of wave, often a DC square wave, that is very
> unhealthy for computers.
>
> - Mike Substelny
>
>
> ------------------------------------------------------------------------
> Before posting messages or replies, see the posting policy rules at:
> www.dmcnews.com/Admin/rules.html
>
> To address comments privately to the moderating team, please address:
> moderator@xxxx
>
> ------------------------------------------------------------------------
> -- Easily schedule meetings and events using the group calendar!
> -- http://www.egroups.com/cal?listname=dmcnews&m=1
>
>
>