Do the '04+ F150's employ positive or negative ground? I THOUGHT I read something about this a few years ago when installing my alarm but for the life of me I cannot be sure. I did a few searches here as well as on the web and cannot find any mention of positive ground, so I thought I'd ask just to be sure.
The reason for my question is I have a power inverter and it does not like positive ground.

Thanks for any info!

 

The neg side of the battery is connected to the frame of the truck.

Some items might switch either power or ground, depending on what it is.

That I recall, only British cars used Pos grounds, but that does not count here, Rover is gone

You should be good to go with the inverter.

 

Ok, you shook more of the cobwebs loose...the positive ground was for my horn, thats why I had to get the relay for the alarm to honk my horn, rather than output to the siren. So my electrical system is negative ground, except for some items, as you mentioned. Thanks for confirming! BTW, I still need to install that damn relay....

 

Actually the horn is switching ground.

I could see where this could get confused, but it is switch of ground, and pos is always hooked up to the horn relay coil.
The neg ground system with the horn is still the same, as are all other items that switch ground on the circuit, vs switching the pos side of the circuit.

I am guessing the output of the alarm is a Pos voltage, and you need to have a relay where this is to the coil ( and ground on the other side of the coil ) and the Normally Open contacts are ground to pin #30, and then 87 to the horn relay ( as if it is from the clock spring in the steering wheel )

 

old volks wagen and porsche's had a postive ground system to. so make it British and German with the wierd stuff.