Well, I was going to mount the intertia switch in the rear part of the trunk, but found out on my wiring harness he has made it just long enough to put it under the dash near where the computer will be. How well does an intertia switch work under the dash? It takes a pretty good hit to set it off and the rear end is the most vital part when I get hit. I would want the intertia switch to switch off the fuel pump MOST if I got rear ended. How well do they work when they are center mounted in the car like under the dash?
EFI intertia switch location?
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reenmachine
20+ Year Stangneter 
Since it's sensing inertia, not direct impact, it should work exactly the same no matter where in the car it's mounted, as long as it's mounted to rigid structure. I don't think I've ever seen an OEM installation that wasn't under the dash somewhere.
reenmachine said:
I'm not sure what cars you are looking at with OEM installations but every Ford I have ever found them in at the salvage yard they have always been installed in the trunk area somewhere. On Mustangs they are right on the back panel and in the onthers I have seen them on the trunk hinge support. I'm not saying some are not installed under the dash but I have never seen any there.....but then again I am usually looking at the same types of cars for the switches.
I think the term interia witch is a misnomer also because they do take a pretty good sharp jarring to trip. I'm assuming that they should work fine under the dash but since I have always seen them in the trunk that is where I installl them and every set of instructions I have ever seen say to install them there as well. In fact the instructions form the Motorsport EFI wiring harness directly from Ford states "The inertia switch should be mounted on a flat surface on the vehicle's rear bulkhead with the plunger pointing upwards."
I just dug those instructions up to to see what they said and they confirm what I already felt to begin with so I personally will stick with trunk installations myself.
reenmachine
20+ Year Stangneter
Hmmm...it's been a while since I've worked on an OEM system I guess 
Regardless, the laws of physics still hold. There will be some amount of energy loss through the car between a rear impact and an underdash-mounted switch, but it will be negligible if the switch is mounted to rigid structure vs. to the dash sheetmetal or something. I think he will be just fine.
Regardless, the laws of physics still hold. There will be some amount of energy loss through the car between a rear impact and an underdash-mounted switch, but it will be negligible if the switch is mounted to rigid structure vs. to the dash sheetmetal or something. I think he will be just fine.
What are you worried about? If you get hit that hard, the explosion from the gas tank is gonna kill you pretty quick, anyway! 
Just in case you are concerned about your life and on the outside chance that you get a fuel cell... you should lengthen the wires to mount it in the trunk... the unibody will absorb alot of energy which may cause the switch to fail.
Just in case you are concerned about your life and on the outside chance that you get a fuel cell... you should lengthen the wires to mount it in the trunk... the unibody will absorb alot of energy which may cause the switch to fail.
WORTH
20+ Year Stangneter
