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

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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...
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Hachiroku ハチロク wrote:

Typical dome light bulb is a dual contact base, he may have caused a momentary short circuit to ground removing the broken bulb. Sounds far-fetched, but possible that that could have damaged something.
nate
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Hachiroku wrote: <snip crap>

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.
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jim beam wrote:

Hi, No way? If short caused a surge in the electrical system, anything is possible. In cases like this mostly nothing serious happens but result unpredictable. Protection is not absolute 100%.
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Bullshit!!
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Mike wrote:

Hmmm, Live little longer and gain some more experience!
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Tony Hwang wrote:

short won't cause voltage surge. measure the voltage across a battery as you increase current load - voltage goes down, not up. only other potential source of surge is back emf from relays, motors, etc, and they're all diode/condenser protected, as is the ecu. bottom line: it's not the dome light.

yeah, it could have been hit by meteorite.

yeah, it could have been hit by meteorite.
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jim beam wrote:

hmmm, Whatever you think. A car battery has lots of energy in it. Think current in this case.
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Tony Hwang wrote:

do what i said - measure voltage as a function of load. then report your results.
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jim beam wrote:

Hmmm, No, current as a function of load! Do you remember the days of generators under the automobile hoods?
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Tony Hwang wrote:

electrical current /is/ load...
take any battery, then measure the voltage as you increase current load on it. then let us know what happens. and how you think high current [short] can cause a "surge".

why? have any basic laws of physics changed since then?
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jim beam wrote:

No. Some times in real world things happen where basic law has difficulty to explain how and why. First thing I learned about generator when I was a kid was polarizing.
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trim posts
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On Sun, 11 Nov 2007 12:23:01 -0500, "Elmo P. Shagnasty"

ok.
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way, way, way too much.
As he always does, apparently. Gary L. Burnore doesn't know how to trim posts.
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Tony Hwang wrote:

bull - that is a function of insufficient learning by the observer.

polarizing is not surge!
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What does that have to do with a car that doesn't contain a generator? What does that have to do with something supposedly related to a battery? Why aren't you answering his questions or providing results of the tests that would prove your "surge" claim invalid?
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I do, and there weren't ECUs then. Basing your argument on something that is now non-existant is very telling.
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A short won't cause a voltage surge.

You might want to try starting with just plain thinking.
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Tony Hwang wrote:

You are utterly without a clue. Best keep quiet.
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