Hardwire Accessory

[Denyse]

I guess this might have gone in the Mercury or Montego areas, but it might be missed there by someone with the expertise with FORD products thatI require, so please forgive my posting it here.

I just purchased a 2007 Montego, and would like to install an electrical accessory that I only want to work when I start the car.

The dealer, says that the car uses a different wiring system that uses something called Ground Switching.

I have tried to ask other people, but all tell me this sounds like bunk, and the dealer just wants me to pay one of their mechanics the hourly rate to attach a hot and ground wire.

Would someone be so kind as to help a "dumb broad" by telling her where to attach a wire (I thought in the fuse box) so it will only work when I start the car? I figure a ground is a ground (right?)

My gateful thanks in advance.

Denyse

[lectra]

I would figure that you should be able to grab a tap off your ignition switch, or even something that already runs while you want the device to run. Other than that, you can just use a relay to do the switching. If it is "ground switched", like he is saying, your voltmeter should tell you this by registering voltage when the "indicator device" (the device you may grab a tap off of) is off, and then go to ground when the device comes on. Other than that, it's as simple as bringing your relay control wire by the wire for the existing device and putting a tap in place. Easy stuff if you can think your way through it. I've done it to my past two cars, myself.

Note: I absolutely, positively do not like ground switching. Not only is it a violation of the NEC (in buildings), but also it can cause all sorts of issues. Many devices are designed expecting your hot wire to be switched, and the ground to be hard wired. If you go ground-switching the device, you could easily fry the device. A short between the ground wire of the device being switched and the chassis could also result in a battery drain (the device being on all the time) on a good day.