Why you should remove the negative battery terminal before doing ANYTHING!!!!

On Sat, 10 Nov 2007 18:04:00 -0800, jim beam wrote:

> Hachiroku wrote:
> <snip crap>
>> I had heard of this before; I can't remember what the car was, but
>> someone shorted out the ECU replacing the dome light...
>
> no way - the ecu's not even connected to the dome light. and they're
> electrically protected against all kinds of "user error", including
> battery reversal, over-voltage, dead shorts and static. short of direct
> lightning strike, water damage, or fire, none of which have a single
> damned thing to do with dome lights, the ecu's not going anywhere and it's
> /certainly/ not going to be fubared by a bulb change.

I talked to him last night. He says he wants you to come out and tell him
why his Pathfinder won't start after changing the dome light...

On Tue, 13 Nov 2007 02:12:44 GMT, Hachiroku ???? >
wrote:

>On Sat, 10 Nov 2007 18:04:00 -0800, jim beam wrote:
>
>> Hachiroku wrote:
>> <snip crap>
>>> I had heard of this before; I can't remember what the car was, but
>>> someone shorted out the ECU replacing the dome light...
>>
>> no way - the ecu's not even connected to the dome light. and they're
>> electrically protected against all kinds of "user error", including
>> battery reversal, over-voltage, dead shorts and static. short of direct
>> lightning strike, water damage, or fire, none of which have a single
>> damned thing to do with dome lights, the ecu's not going anywhere and it's
>> /certainly/ not going to be fubared by a bulb change.
>
>I talked to him last night. He says he wants you to come out and tell him
>why his Pathfinder won't start after changing the dome light...
>

Anybody that says a short on a voltage line can't hurt an ECU has
never worked on computers.....

--
Scott in Florida

I'm doing great!

Thank you.

If anything is connected to the BCM, it will be in someway connected to the
ECM. Through a Bus or a connector.

RK
"Hachiroku ????" > wrote in message
news:GGOZi.10705$h61.8533@trndny02...
> On Mon, 12 Nov 2007 01:54:05 +0000, Refinish King wrote:
>
>> On about 92 and up:
>>
>> The dome light is connected to the Body Control Module.
>>
>> RK
>
> Hey, RK, how ya doin'?
>
> I wanted to ask you something a while ago, but I forget.
>
> At any rate, right. The DL is connected to the BCM, which MAY have a
> connection to the ECM.
>
>
>> "jim beam" > wrote in message
>> ...
>>> Tony Hwang wrote:
>>>> Gary L. Burnore wrote:
>>>>
>>>>> On Sun, 11 Nov 2007 02:17:38 GMT, Tony Hwang > wrote:
>>>>>
>>>>>
>>>>>> jim beam wrote:
>>>>>>
>>>>>>
>>>>>>> Hachiroku wrote:
>>>>>>> <snip crap>
>>>>>>>
>>>>>>>> I had heard of this before; I can't remember what the car was, but
>>>>>>>> someone
>>>>>>>> shorted out the ECU replacing the dome light...
>>>>>>>
>>>>>>>
>>>>>>> no way - the ecu's not even connected to the dome light. and
>>>>>>> they're electrically protected against all kinds of "user error",
>>>>>>> including battery reversal, over-voltage, dead shorts and static.
>>>>>>> short of direct lightning strike, water damage, or fire, none of
>>>>>>> which have a single damned thing to do with dome lights, the ecu's
>>>>>>> not going anywhere and it's /certainly/ not going to be fubared by a
>>>>>>> bulb change.
>>>>>>
>>>>>> Hi,
>>>>>> No way? If short caused a surge in the electrical system,
>>>>>
>>>>>
>>>>> You're kidding right?
>>>> Hi,
>>>> Probably you don't even know basic Ohm's law or Kirchoff's or Tevnin
>>>> Norton's theorem, etc. If you want to debate, email me directly. Let's
>>>> compare our CV first.
>>>
>>> tony, this is usenet - "credentials" don't mean ****. just stick to the
>>> facts.
>>>
>>> fact 1 - batteries don't "surge". period. some [reactive] peripherals
>>> can do it, unless protected. in cars, they all are. dome lights are
>>> not reactive.
>>>
>>> fact 2 - ohmic behavior dictates that battery voltage drops as current
>>> increases, not the other way around.
>>>
>>> fact 3 - ecu's are "idiot proofed". per #1, a dome light has no
>>> reaction that could possibly cause a problem, even if the ecu was
>>> unprotected.
>>>
>>> conclusion: either address reality or move on.
>

The BCM is always communicating with the ECU!

RK
"jim beam" > wrote in message
t...
> Refinish King wrote:
>> On about 92 and up:
>>
>> The dome light is connected to the Body Control Module.
>
> yes, which is not the ecu!
>
>
>>
>> RK
>> "jim beam" > wrote in message
>> ...
>>> Tony Hwang wrote:
>>>> Gary L. Burnore wrote:
>>>>
>>>>> On Sun, 11 Nov 2007 02:17:38 GMT, Tony Hwang > wrote:
>>>>>
>>>>>
>>>>>> jim beam wrote:
>>>>>>
>>>>>>
>>>>>>> Hachiroku wrote:
>>>>>>> <snip crap>
>>>>>>>
>>>>>>>> I had heard of this before; I can't remember what the car was, but
>>>>>>>> someone
>>>>>>>> shorted out the ECU replacing the dome light...
>>>>>>>
>>>>>>> no way - the ecu's not even connected to the dome light. and
>>>>>>> they're electrically protected against all kinds of "user error",
>>>>>>> including battery reversal, over-voltage, dead shorts and static.
>>>>>>> short of direct lightning strike, water damage, or fire, none of
>>>>>>> which have a single damned thing to do with dome lights, the ecu's
>>>>>>> not going anywhere and it's /certainly/ not going to be fubared by a
>>>>>>> bulb change.
>>>>>> Hi,
>>>>>> No way? If short caused a surge in the electrical system,
>>>>>
>>>>> You're kidding right?
>>>> Hi,
>>>> Probably you don't even know basic Ohm's law or Kirchoff's or
>>>> Tevnin Norton's theorem, etc. If you want to debate, email me directly.
>>>> Let's compare our CV first.
>>> tony, this is usenet - "credentials" don't mean ****. just stick to the
>>> facts.
>>>
>>> fact 1 - batteries don't "surge". period. some [reactive] peripherals
>>> can do it, unless protected. in cars, they all are. dome lights are
>>> not reactive.
>>>
>>> fact 2 - ohmic behavior dictates that battery voltage drops as current
>>> increases, not the other way around.
>>>
>>> fact 3 - ecu's are "idiot proofed". per #1, a dome light has no
>>> reaction that could possibly cause a problem, even if the ecu was
>>> unprotected.
>>>
>>> conclusion: either address reality or move on.
>>

It could be a coincidence?

Maybe there is another problem.

RK
"Hachiroku ????" > wrote in message
news:wK7_i.1806$eV.1247@trndny04...
> On Sat, 10 Nov 2007 18:04:00 -0800, jim beam wrote:
>
>> Hachiroku wrote:
>> <snip crap>
>>> I had heard of this before; I can't remember what the car was, but
>>> someone shorted out the ECU replacing the dome light...
>>
>> no way - the ecu's not even connected to the dome light. and they're
>> electrically protected against all kinds of "user error", including
>> battery reversal, over-voltage, dead shorts and static. short of direct
>> lightning strike, water damage, or fire, none of which have a single
>> damned thing to do with dome lights, the ecu's not going anywhere and
>> it's
>> /certainly/ not going to be fubared by a bulb change.
>
> I talked to him last night. He says he wants you to come out and tell him
> why his Pathfinder won't start after changing the dome light...
>
>

On Tue, 13 Nov 2007 02:21:29 +0000, Scott in Florida wrote:

> On Tue, 13 Nov 2007 02:12:44 GMT, Hachiroku ???? > wrote:
>
>>On Sat, 10 Nov 2007 18:04:00 -0800, jim beam wrote:
>>
>>> Hachiroku wrote:
>>> <snip crap>
>>>> I had heard of this before; I can't remember what the car was, but
>>>> someone shorted out the ECU replacing the dome light...
>>>
>>> no way - the ecu's not even connected to the dome light. and they're
>>> electrically protected against all kinds of "user error", including
>>> battery reversal, over-voltage, dead shorts and static. short of
>>> direct lightning strike, water damage, or fire, none of which have a
>>> single damned thing to do with dome lights, the ecu's not going
>>> anywhere and it's /certainly/ not going to be fubared by a bulb change.
>>
>>I talked to him last night. He says he wants you to come out and tell him
>>why his Pathfinder won't start after changing the dome light...
>>
>>
> Anybody that says a short on a voltage line can't hurt an ECU has never
> worked on computers.....


He said there was a spark when he tried to remove the bulb. The bulb's
glass was broken, and he tried to grab it without touching anything else,
but there was a spark, and when he tried to start the truck...nothing.

He had it towed to a Nissan dealer. They're trying to find a used ECU and
told him that before doing ANYTHING electrical with the truck he should...

disconnect the negative battery terminal...

(Next week he's removing the terminal and installing a Negative Terminal
Shut-off...)

On Nov 11, 3:48 pm, "Steve W." > wrote:
> > tony, this is usenet - "credentials" don't mean ****. just stick to the
> > facts.
>
> > fact 1 - batteries don't "surge". period. some [reactive] peripherals
> > can do it, unless protected. in cars, they all are. dome lights are
> > not reactive.
>
> No but a direct short could cause a problem in the item shorted. In the
> case of some vehicles that could be the BCM if they use it for things
> like an interior light timer/dimmer (close door and dome light stays on
> for a bit) Shorting that circuit cause problems.
>
>
>
> > fact 2 - ohmic behavior dictates that battery voltage drops as current
> > increases, not the other way around.
>
> Yes BUT take a chunk of wire and toss it across the battery. Measure the
> battery voltage. It likely won't cause a voltage drop as it heats up and
> melts.
>
>
>
> > fact 3 - ecu's are "idiot proofed". per #1, a dome light has no
> > reaction that could possibly cause a problem, even if the ecu was
> > unprotected.
>
> VERY WRONG. ECUs are easy to kill if you are not paying attention. My
> SOP in the body shop is to pull the ECU on anything that rolls in for
> panel work. One good zap from a welder can kill the ECU without being
> near it.
>
>
>
> > conclusion: either address reality or move on.
>
> --
> Steve W.
> Near Cooperstown, New York
> NRA Member
> Pacifism - The theory that if they'd fed
> Jeffrey Dahmer enough human flesh,
> he'd have become a vegan.

Guys, guys... go get a schematic and find out if the dome light is in
the same circut as the ECU. Even if it is, I don't think the changing
of the bulb is what caused the problem. I do think that whatever
caused the light to function intermittantly MIGHT have cused the ECU
problem. Either way, if the light was working sometimes, that would
tell me that there was nothing wrong with the bulb. Funny thing about
light bulbs... they either work, or they don't. The filament is either
complete, or it's not. It doesn't go back once it's blown. Okay, so if
there's a short, it would be either in the fixture, or in the wires
going to it. Furthermore, That's what fuses are for! I've done it many
many times. Shorting things out and blowing fuses and replacing them
again. The fuse opens the circut in the event of a short before
ANYTHING gets damaged (unless the fuse is either disregarded, or
replaced with a fuse of a higher amperage). And furthermore, since
we're on the topic of fuses, this is the whole reason that things like
dome lights and tail lights and headlights and radios and ESPECIALLY
ECU's are all on thier own circuts with thier own fuses. Kind of
insurance, if one thing blows a fuse, you don't lose everything at
once. I do agree with the titlehead of this issue, being "disconnect
the negitive before working". But this rule is mostly in place because
sometimes people like to play with the wires and accidently drop the
exposed end of a hot wire onto the bare frame of body of the vehicle.
The result can be a blown fuse at minimum, or a small fire at most
(I've been there, too). However, I regress (and conclude), the dome
light bulb cannot be the reason for ECU problems. ECU's may or may not
be "idiot proofed," but they are not on the same circut as the dome
light, the dome light cannot cause "power surges" and niether can
anything else on a vehicle, and even if anything were to happen, the
fuses would have caught it. Case Closed. Go get a new ECU, and re-wire
your dome light. quit griping about crap that is not relevant. The
more you gripe, the more other people despise you, and the job still
is not done.

On Tue, 13 Nov 2007 04:33:54 +0000, fury45iii wrote:

> Guys, guys... go get a schematic and find out if the dome light is in the
> same circut as the ECU. Even if it is, I don't think the changing of the
> bulb is what caused the problem. I do think that whatever caused the light
> to function intermittantly MIGHT have cused the ECU problem. Either way,
> if the light was working sometimes, that would tell me that there was
> nothing wrong with the bulb. Funny thing about light bulbs... they either
> work, or they don't. The filament is either complete, or it's not. It
> doesn't go back once it's blown. Okay, so if there's a short, it would be
> either in the fixture, or in the wires going to it. Furthermore, That's
> what fuses are for! I've done it many many times. Shorting things out and
> blowing fuses and replacing them again.


Yeah, but we're talking a Nissan here! I've seenthings in Nissans I've
never seen in other cars.

And, he said the glass was broken. How it even lit without burning out is
a mystery!

On Nov 11, 3:48 pm, "Steve W." > wrote:

> VERY WRONG. ECUs are easy to kill if you are not paying attention. My
> SOP in the body shop is to pull the ECU on anything that rolls in for
> panel work. One good zap from a welder can kill the ECU without being
> near it.

A welder and a dome light are vastly different things. An arc
welder generates a HUGE reactive voltage spike when striking the arc,
and that spike can wander all over the entire vehicle and fry
sensitive electronics and not-so-sensitive things, too, like
alternator diodes. Standard procedure there is to disconnect the
battery whenever doing any welding on the thing. Shorting a dome light
will NOT generate any sort of spike. Period. You need a coil to
generate spikes, coils like those found in starters, alternator
rotors, ignition coils. You might as well try to generate a spike by
disconecting and reconnecting the battery.

Dan

wrote:

> On Nov 11, 3:48 pm, "Steve W." > wrote:
>
>
>>VERY WRONG. ECUs are easy to kill if you are not paying attention. My
>>SOP in the body shop is to pull the ECU on anything that rolls in for
>>panel work. One good zap from a welder can kill the ECU without being
>>near it.
>
>
> A welder and a dome light are vastly different things. An arc
> welder generates a HUGE reactive voltage spike when striking the arc,
> and that spike can wander all over the entire vehicle and fry
> sensitive electronics and not-so-sensitive things, too, like
> alternator diodes. Standard procedure there is to disconnect the
> battery whenever doing any welding on the thing. Shorting a dome light
> will NOT generate any sort of spike. Period. You need a coil to
> generate spikes, coils like those found in starters, alternator
> rotors, ignition coils. You might as well try to generate a spike by
> disconecting and reconnecting the battery.
>
> Dan
>
Hmmm,
Lamp filament is a tiny coil, LOL!