INERTIAL SHUTOFF SWITCH WIRING

[RRoller123]

I bought a Ford XF3Z9341AA inertial shutoff switch to shut the fuel pump off in the event of an accident.

I need to know how to wire it, as it is not obvious. There are 3 terminals, labeled:

NO
C
NC

I was thinking that I would just wire this in line with the pump, but maybe it should be wired as a trigger to a relay for shutoff?

Anyone use this switch and know what's what? My next stop is a Ford dealer, but I thought I would start here.

Thanks.

Pete

[spider2081]

The switch is a little pricey so not knowing its current carrying capacity I would use it to trigger a relay. I Googled the part number and was not able to find its capacity.

The C is the movable part of the switch
The NC is the contact that the movable part normally contacts. This connection opens when the "G" force is exceeded.
The NO is the contact that movable part will contact when the "G" force is exceeded.

You will connect the relay coil through the "G" switch C and NC contacts. This will hold the relay closed. If the "G" force is exceeded the switch opens the relay coil circuit.

Hope this helps

[RRoller123]

Awesome, thanks for the info! I just went over to the local Ford dealer ( this is my summer "staycation" while I care for my dear wife) and asked them about it and they basically said the same thing, but they wire it directly to the fuel pump feed, without a relay. It seems that the feed TO the FP goes to the center lead "C" and then out to the FP goes to the "NC". My guess is that stands for "normally connected", and the NO likely stands for "normally closed". They said NO was unused in any applications they knew of, maybe on a some dual pump or foreign job cah.

[wizard124]

Is there a specific mounting orientation for that swiitch to work?

[RRoller123]

They are 3-d, all axes.

[perthling]

NO and NC refer to the switch state - Normally Open and Normally Closed.

If you wired to the NO side in line with the fuel pump you would have no circuit as the switch is normally open.

[RRoller123]

This thing is a pain in the ass. There is no standard connector that will fit on the odd sized pins (they are wider than standard), and they are spaced so closely together that even if you modified/widened out a smaller Molex type female, they likely would touch side-side.

So the choice is to either solder directly to the terminals, which will require cutting away some of the plastic housing for access, or to pay Ford about 50 bucks for the custom mating connector with pigtail wires. Soldering directly to the terminals could damage the unit by heat, so I am tempted to swallow the cost and buy the damned connector. No wonder the big 3 are profitable again.

[divace73]

This thing is a pain in the ass. There is no standard connector that will fit on the odd sized pins (they are wider than standard), and they are spaced so closely together that even if you modified/widened out a smaller Molex type female, they likely would touch side-side.

So the choice is to either solder directly to the terminals, which will require cutting away some of the plastic housing for access, or to pay Ford about 50 bucks for the custom mating connector with pigtail wires. Soldering directly to the terminals could damage the unit by heat, so I am tempted to swallow the cost and buy the damned connector. No wonder the big 3 are profitable again.

couldn't you get one from a wrecker for almost nothing??

[vandor]

That's what I was thinking, just go to you local Pick n Pull.
It would be easy to wire it to an FI fuel pump's ground wire by them left rear taillight.

[RRoller123]

That's a REALLY good idea, (which is why it escaped me). Anyone know where these are mounted on Ford products? It is going to be about 90 and humid today, perfect for scrounging around a junk yard!

Pete

[RRoller123]

Thanks for the idea Csaba. So that worked out perfectly. There is a Pick and Pull in Millis, MA on Rt. 109, for future reference. 2 bucks entry fee, 3.99 for the connector and wires. Found it in 5 minutes.

For those thinking of doing this mod, and willing to use a used Inertial Switch, I can tell you that I found the inertial switch in a Ford Explorer, mounted on the inside of the passenger side firewall below the glove box. Not hidden by carpet. The red reset button faces UP. I was able to get about 8" of wire with the connector before I had to cut it.

One thought on this: The mass difference between a Ford Explorer and a Fiat Spider is, shall we say, significant. Since I only wanted the cable and connector, it didn't matter to me, but it occurs to me that there may be different calibrations of these switches for different mass cars. The same impact force on a Focus is going to yield very different G forces than that same impact on an Explorer. I am just speculating here, but it might be wiser to pick a switch and the cable from the Focus versus the Explorer or a truck, say, in order to get one that will react more like we would expect in a Spider? I don't know if Ford, etc. have various Inertial Switches for their various weight-class vehicles, but we don't want these things triggering on bad potholes.

[nibbes123]

Hi RRoller123 here is a PDF of hook up of the switch.

[PDF]
INERTIA ACTIVATED FUEL PUMP CUT-OFF SWITCH FCS1
http://www.oemautoparts.net/downloads/IS31.pdf
BEFORE INSTALLING THE INERTIA SWITCH. The inertia Switch is a device intended to automatically shut off the supply of fuel to the engine following a heavy.

[donm]

When I did this mod 2 years ago, I bought the switch new from a Ford dealer and he said the switches are the same across their vehicle line, and the third terminal is for a dashboard warning light to warn you if the switch is tripped.

I mounted it in the trunk on the upright column by the left wheel well. I hooked it up by soldering small female push-on connectors to the pump wires. If you have the facit electric pump like I have you don't need a realy--it doesn't draw that much current.

[RRoller123]

Thanks fellows. Here is what I did this afternoon:

Got the connector and leads from the Pick and Pull in Millis:



Mounted it on the back wall next to the battery, and ran the leads in through the wall to catch the fuel pump feed under the rear carpet. On my car, the FP is fed through the interior, under the carpet about midway across the cab. This way, there are no penetrations to the outside. You need to pull the rear seats, and you need 2 grommets, as there is an ~2" air gap between the sheet metal in the trunk and the sheet metal in the back seat. i.e. 2 penetrations to get the wires inside the cab.





Took a test drive and all works well! I did accidentally drop the switch while working on installing it, and it tripped, so I know it works.

[nibbes123]

Where is the fuel pump located? In the car or in the engine cabin ? Also how did you you use to feed power to the pump?