Why you should remove the negative battery terminal before..

I personally have seen a bunch of blown ECU's caused by wiring shorts,
mostly fuel pumps, but other things too.

Sure the ECU is 'protected' by a diode, but no one sells the damn diode
to replace the blown one nor do many 'authorized' places exist to fix
them. Half are sunk in a block of plastic also.

I have repaired a few by using a cheap diode with a +/- 10 to 15%
tolerance so they fell close to the original specs. Close enough to work.

If the dome light is on a timer, it is connected to some kind of
computer....

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
'New' frame in the works for '08

Hachiroku ハチロク wrote:
> I was lokking thorugh the Subaru manual to find out where the thermostat
> was. I'm used to it being on TOP of the engine.
>
> While it ididn't show the location, it did say, "Remove negative battery
> terminal, and remove thermostat housing..."
>
> Huh? Remove the - terminal berfore removing the thermostat housing?! WTF?!?!
>
> Last night I went to pick up my papers for my "paper route" and saw a
> big-ass GMC pickup I hadn't seen before. Then I saw one of my firend's
> fathers, who started doing the papers about 10 days after I did. He
> usually drive an '01 Pathfinder.
>
> "Where's the Pathfinder?" "I wrecked it." "WHAT?!?!?!?!"
>
> Well, he didn't really wreck it. He had a bad bulb in the overhead light.
> He removed the lens, and the bulb was in pieces, but still working
> intermittantly. He removed the bulb and replaced the lens, and then tried
> to start the truck. No Go. The starter spins, but the engine doesn't catch.
>
> Looks like he fried the ECU!!!! All the other lights work, the dome light
> works, but the fuel pumpo doesn't energize. He tried the reset procedure
> and nothing.
>
> I had heard of this before; I can't remember what the car was, but someone
> shorted out the ECU replacing the dome light...
>
>
 >> Stay informed about: Why you should remove the negative battery terminal before.. 

Scott Dorsey wrote:
> jim beam <spamvortex.TakeThisOut@bad.example.net> wrote:
>> with an air core and virtually no inductance. if you have instruments
>> that can measure any voltage spike you get from a coiled bulb filament,
>> i'd love to see your readings.
>
> I do.
>
> BUT, you don't need one. If you have an 1141 lamp with 50 loops of
> 1/16" (that's estimated by eye here) about 1/2" long, you can use
> Wheeler's Formula:
>
> 50^2 * (0.065)^2 10.5
> --------------- = ----- = 0.27 microhenries
> 18 * 0.065 + 40 * 0.5 28.0
>
>
> That's a lot less than the hundreds of henries that an arc welder ballast
> will have, and it's probably small enough to be compensated for by the
> capacitance of the wiring, even.

excellent. and it's /well/ below any level that could /possibly/ impact
the ecu!


> But it's enough that you could measure it
> carefully with a scope and a pulse generator, even though it's actually
> going to be swamped at any reasonable voltage by the nonlinearity when the
> filament heats up and its resistance increases.

indeed.
 >> Stay informed about: Why you should remove the negative battery terminal before.. 

"Hachiroku ????" <Trueno RemoveThis @AE86.gts> wrote in message
news:lzt_i.7967$ds.6186@trndny09...
> 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!
>
>

First you said that the bulb was in pieces, not that the glass was broken.
Was it really broken?
I have seen several times that the glass part of a bulb can separate from
its socket but still hanging by the leads it may still work.
And I have also seen that the ends of a broken lamp filament can dangle
together and get get kind of welded together, so it works again, but usually
not for long.
What may kill an ECU is the very very short transients in voltage when a
cirquit somewhere in the system is abruptly opened or closed, especially
when it is high current (a short) and/or repeated many times. If he made a
momentarily short cirquit while changing the bulb that MAY be enough.
That is why with modern cars we are advised not to use jumper cables without
transient suppressors.

Asbj�rn
 >> Stay informed about: Why you should remove the negative battery terminal before.. 

Hello:

This might seem odd to you but, newer cars use bulbs that are a specific
impedance. A 2157 is the same candle power as an 1157, but the impedance is
higher. That's why if you use a 2157 in place of a 3057 for argument's sake.

You'll get a check engine light in an OBD2 compliant vehicle.

RK
"Tony Hwang" <dragon40.RemoveThis@shaw.ca> wrote in message
news:zou_i.208792$th2.154494@pd7urf3no...
> Dan_Thomas_nospam.RemoveThis@yahoo.com wrote:
>
>> On Nov 11, 3:48 pm, "Steve W." <csr684....RemoveThis@yahoo.com> 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!
 >> Stay informed about: Why you should remove the negative battery terminal before.. 

The very reason that using a wrong bulb:

Will set a code on an OBD2 system.

RK

PS
I'm not speculating on Jim's method of earning a living. But there are such
instruments available.
"jim beam" <spamvortex DeleteThis @bad.example.net> wrote in message
news:eK-dnSP_xrPhEqfanZ2dnUVZ_qHinZ2d@speakeasy.net...
> Tony Hwang wrote:
>> jim beam wrote:
>>
>>> Tony Hwang wrote:
>>>
>>>> Dan_Thomas_nospam DeleteThis @yahoo.com wrote:
>>>>
>>>>> On Nov 11, 3:48 pm, "Steve W." <csr684... DeleteThis @yahoo.com> 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!
>>>
>>>
>>> with an air core and virtually no inductance. if you have instruments
>>> that can measure any voltage spike you get from a coiled bulb filament,
>>> i'd love to see your readings.
>> Hmmm,
>> You are so bone headed, can't even take a joke.
>> The more you babble, the more you reveal your lack of knowledge:
>> pratical or thory. My job used to deal with fraction of nano amps. VLSI,
>> ASIC, etc. on mil-spec.
>
> bullshitting idiot.
 >> Stay informed about: Why you should remove the negative battery terminal before.. 

Refinish King wrote:
> The very reason that using a wrong bulb:
>
> Will set a code on an OBD2 system.

that's load measurement, not inductance from a bulb filament coil.


>
> RK
>
> PS
> I'm not speculating on Jim's method of earning a living. But there are such
> instruments available.

of course! but i bet t.h. doesn't have any, and i'll bet he doesn't
know how to measure whether it has any noticeable effect!



> "jim beam" <spamvortex.DeleteThis@bad.example.net> wrote in message
> news:eK-dnSP_xrPhEqfanZ2dnUVZ_qHinZ2d@speakeasy.net...
>> Tony Hwang wrote:
>>> jim beam wrote:
>>>
>>>> Tony Hwang wrote:
>>>>
>>>>> Dan_Thomas_nospam.DeleteThis@yahoo.com wrote:
>>>>>
>>>>>> On Nov 11, 3:48 pm, "Steve W." <csr684....DeleteThis@yahoo.com> 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!
>>>>
>>>> with an air core and virtually no inductance. if you have instruments
>>>> that can measure any voltage spike you get from a coiled bulb filament,
>>>> i'd love to see your readings.
>>> Hmmm,
>>> You are so bone headed, can't even take a joke.
>>> The more you babble, the more you reveal your lack of knowledge:
>>> pratical or thory. My job used to deal with fraction of nano amps. VLSI,
>>> ASIC, etc. on mil-spec.
>> bullshitting idiot.
>
>
 >> Stay informed about: Why you should remove the negative battery terminal before.. 

jim beam wrote:

>
> excellent. and it's /well/ below any level that could /possibly/ impact
> the ecu!
>

You seem to forget that the dome light is 'live' all the time using a
ground as a switch.

They can have the glass fall out of the base and the loose internal
connecting wire(s) can and will cause a short circuit. This happens all
the time with bulbs such as the 1157 in taillights.

Short circuits can do nasty things to computers like blow the input
diode 'before' the fuse has a chance to blow.

It's not like the designers of modern vehicles are just BSing when they
say to unhook the negative before working on them.....

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
'New' frame in the works for '08
 >> Stay informed about: Why you should remove the negative battery terminal before.. 

Hachiroku ハチロク wrote:
\
>
> Well, he didn't really wreck it. He had a bad bulb in the overhead light.
> He removed the lens, and the bulb was in pieces, but still working
> intermittantly. He removed the bulb and replaced the lens, and then tried
> to start the truck. No Go. The starter spins, but the engine doesn't catch.
>
> Looks like he fried the ECU!!!! All the other lights work, the dome light
> works, but the fuel pumpo doesn't energize. He tried the reset procedure
> and nothing.
>
> I had heard of this before; I can't remember what the car was, but someone
> shorted out the ECU replacing the dome light...
>
>

I don't buy it. ECUs are actually *very* well protected against
intermittent faults, voltage spikes, etc. (Zener diodes are a wonderful
thing). 99.9% of the "failed" ECUs people pull out of cars are actually
fine and the problem lies elsewhere. There's no WAY you can hurt one
just changing a light bulb.
 >> Stay informed about: Why you should remove the negative battery terminal before.. 

Tony Hwang wrote:

> jim beam wrote:

>> yeah, it could have been hit by meteorite.
>
> hmmm,
> Whatever you think. A car battery has lots of energy in it.
> Think current in this case.

Think "fuse" in this case.... unless it was one of those Chinese-made
fuses from Harbor Freight...
 >> Stay informed about: Why you should remove the negative battery terminal before..