Is it officially nonsense about jump-starting and pulling the auto-transmission fuse?

[DL4567]

I recently had to jump-start my car, and being on the forums since 2004, I remembered reading about pulling the auto transmission fuse when doing so just in case, so I still did it just to be sure. It was by far the biggest pain in the ass of the whole jump-starting process. That got me thinking to research it again, and all I could find was this thread:

http://dmctalk.org/showthread.php?3196

Elvis was the most vocal in post #17 about it being total misinformation, but I just wanted to put the question out there again, is it totally unnecessary to pull that fuse?
I have DMC Midwest's new digital shift-computer, and I'd hate for anything to happen to it. It seems the biggest danger mentioned in the above linked thread is reversing the polarity of the cables or accidentally touching the ends together even for a split-second. But assuming you are very careful and don't do those bad things, please tell me the fuse can stay put without any worry whatsoever to the shift-computer....

[Michael]

Are not the fuses in place to protect the components?

Seems like if you do anything worst case you blow a fuse. I have boosted my car off from a power pack several times.

[dmcnc]

I've done the same without pulling any fuses and no issues.

[Dangermouse]

I would suspect that early failures of the AT governor were initially blamed on owners jumping their car, rather than components drying out. P

[eseethal]

Jump-starting is always a bit of a risk for electronic components. Spikes of higher voltage are possible. I just worked on a Hummer H3 which supposedly had it's ECU fried due to frequent jumpstarting. Jump-Starting just with a battery is much safer. Do not have the engine running before you connect to the car you want to start. The fuses won't protect here anything, fuses just protect from higher currents and not higher voltage.

Eugen

[Bitsyncmaster]

Are not the fuses in place to protect the components?

Seems like if you do anything worst case you blow a fuse. I have boosted my car off from a power pack several times.

Most often fuses don't protect electronic components. It takes a 20 amp fuse about 50 ms. to blow with a 100 amp load (short circuit) and running near 25 amps it can take 10 min. to blow.

Car electronics need to be designed with a lot of protection against voltage variations and noise caused by inductive load switching.

[Jonathan]

I would suspect that early failures of the AT governor were initially blamed on owners jumping their car, rather than components drying out. P

I think this is more along the lines of where the rumor came from. Misinformation back in the day and not knowing what really caused the problem.

I have always been suspicious of the inertia switch recall for much the same reason. I have never opened up the electronics or done any detective work to confirm it, but I think the whole inertia switch recall revolved around the ability to whack the car from the outside in the wheel well and get the door locks to open. The recall was first to move the switch and then soon after replace it and move it and I just don't buy it. I think replacing it was just cover for moving it away from the door lock opening whacking spot and had nothing to do with it failing internally.

[Dangermouse]

I assume the biggest risk would be connecting the jumper leads (correctly) and minimizing the amount of arcing between the clips and the post you are connecting to. As opposed to the actual charging of the D's battery from another source.

As such, if the donor/charging vehicle is off, the voltage at the ends of the leads would be around 12.5V whereas it would rise to 14.5V if the donor vehicle was running. Higher voltage - larger spark/arc.

[Jonathan]

Wasn't there a warning for our cars not to jumpstart directly at the battery as opposed to using the posts in the engine bay? Would that have been where damage to the shift computers could have come from?

[David T]

IMHO the problems with the shift computers were not caused by "jumping" the cars. Those caps would blow anyway and seem to be blown in just about every automatic car eventually. The bad solder connections are not caused by jumping and the blown transistors are caused by melted wiring. It certainly can't hurt to pull the fuse but isn't necessary. Jumping cars can be very dangerous to the cars AND the people which is why it is now discouraged. If you do it wrong you can blow all of a car's electronics and explode the battery. On newer cars all of those electronic boxes can get VERY expensive! Jumping a car should be considered an emergency procedure. Either charge the battery replace the battery, it's safer. If you find you are jumping a car often, find and fix the problem. If you must jump a car the safest way to do it is with a battery pack. That way if you mess up you only damage ONE car!

[DMC5180]

Wasn't there a warning for our cars not to jumpstart directly at the battery as opposed to using the posts in the engine bay?

Yes, but the reason not to jump start at the battery is for safety. Potential explosive gases venting near the battery. Even in traditional engine compartment battery locations, they tell you to always attach the negative jumper cable to a suitable chassis ground away from the battery.




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[David T]

Too hard on a Delorean to get to the battery terminals, especially the negative one. That is why they added the jumper terminal, not for safety, for convenience.

[DMC5180]

Both go hand in hand: Safety & Convenience


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[Ron]

Too hard on a Delorean to get to the battery terminals, especially the negative one. That is why they added the jumper terminal, not for safety, for convenience.+1
Not to mention it eliminates several connections and feet of cable power would have to flow through...