The Treehouse Blog

Tag: inertia switch

Vehicle Work

by on Mar.27, 2011, under Happenings

Firstly, I’m not a mechanic, but with electrical problems I’m willing to take a stab.

A few weeks ago, I was driving my truck (2005 Ford Ranger) back from a hike with a friend when the engine stopped.  I shifted into neutral and tried to restart, and it would crank but that’s it.  We got pushed off the road and checked for fluid leaks, etc.  Eventually I decided to try the fuel pump shutoff inertia switch and the truck started immediately.  I wasn’t completely convinced this was the problem – that maybe whatever the problem was had resolved itself around the time I reset the switch.  There was no jolting of the vehicle that should have set off the switch.  Researching the problem online, there was some indication that passenger’s wandering feet are sometimes the cause of the problem, as the switch is located in the passenger foot-well, and other indications that if it trips once reset it, if it trips twice, replace it.  I was content to reset and forget, as my passenger also indicated he may have been repositioning his feet when it happened.

A week later, the switch tripped again.  The same passenger was present, but this time there was no recollection of any bad feet positioning.  Resetting the switch was the first remedy attempted and was immediately successful.  It was now clear that replacing the switch would be the next step.  Researching Ford’s parts database found that in addition to a replacement switch, a “conversion kit” was available that would move the switch from its foot-well location to behind the trim panel (“cowl”) next to the fuse box.  I had initially decided against this (it was 4x as expensive), but the Ford dealer indicated that the kit was the appropriate resolution, so I bought one.

Installation was very straightforward, though it is difficult to position your drill in the necessary orientation to drill the pilot holes for the switch mounting bracket.  After breaking the head off a ground screw while trying to remove it (remedy: different screw), and breaking the pop-off holding the cowl in place (remedy: zip tie), the switch was finally in place.  Upon starting the vehicle, however, the airbag light began flashing a sequence.  Panic.  Must have drilled through airbag wiring or something.  No!

Fortunately, Google translated that code “27” was indicating that the passenger airbag off light was burned out.  Interesting coincidental timing.  So, I disassembled the portion of the dash and removed the offending keyswitch/light module for a little repair work.  I de-soldered the light and replaced it with a resistor and LED.  It ended up being a lot dimmer than the factory bulb, but the airbag computer is fine with it.

So far, so good.  Hopefully no relapse is on the horizon.


My Haynes Repair Manual does little more than acknowledge the existence of the fuel pump inertia switch and air bag system, so here are some of the resources I found.

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