Anybody know how I can get a +12v source when the inition switch is switched to the on / run position. I have a 2005 F250 XL. John.

 

I'm not sure about the 2005's but the older ones (eg 2003) have a "customer access" wire on fuse # 29 which is a 10 Amp circuit. Locate your OBD II plug under the dash and follow it's wire bundle up towards the radio. You should have a white with blue tracer wire which is capped off with a black heat-shrink piece and that is taped to this wire bundle. Power is on in "RUN" only.

 

The 2005 and 2006's have the same customer access wire.


Here's a pic:

http://www.pbase.com/image/57277770.jpg

 

any idea for a 20 amp circuit? (for an air horn)

 

The powerpoint/cigarette lighter runs on a 20 amp circuit.

(actually I know it runs thru a 20 amp fuse, not sure if that means its a 20 amp circuit)

If you look in your owners manual they show you a fuse diagram with what each fuse runs to and the Fuse Amp Rating.

 

For my air horn, I tapped into one from the tow package. It runs right along the drivers side frame rail. I believe it was yellow. Use a multi-meter on the power plug at your hitch to determine the color and key on/off state.

 

I thought this was exactly what I needed, but either I didn't find the right wire, or it isn't quite what I'm looking for. I found a white wire with a blue trace, in what I think was the right location (behind the "ash tray"). It was a stub, and it only comes on when the key is in "run". However, the voltage isn't constant. It seems to increase with engine temperature, although I can't be sure of that. Seems like the voltage starts around 11.5V, gradually increases, then tops out around 13.9V.

I guess for many applications this would be fine. I need the power for my radar detector, however, and that seems to be voltage sensitive. Below about 12.? V, it behaves crazy. I could almost live with it, since the whacky behavior only lasts a few minutes (or less?), except part of the whacky behavior is incessant chirping. Drives me nuts.

Anyways, did I find the right wire, and this is what it does? Or did I find a different wire?

thanks,
-robert

 

i have upfitter switches on ebay. and then you would still have three switches to do whatever else with the upfitter switches only go hot with the ignition on. and there is an article here somewhere on how to make the switch momentary.

 

Thanks for the offer. I have factory upfitter switches, and that was what I was planning to use originally. Researching how to tap into them I came upon this thread, and thought this was and even better deal - on only when the key was turned to "run". I guess I'll go back to the upfitter switches.

What do you mean "make the switch momentary"?

thanks,
-robert

 

you can make it so it only supplies power when you are holding it on and when you let go it turns off

 

That sounds awesome. I'm going to install a winch soon, and that would be very handy.

 

it looks like it was real easy too you just have to remove a little piece of plastic or add one in i am not sure as i read the article a while back

 

ohh and are you sure that the wire you tested goes up with engine temp and not engine speed cause some of the trucks have speed sensitive cd players

 

The voltage did not go up if I revved the engine, so I'm pretty sure it wasn't engine speed.

My radio/CD has an adjustment to get louder as the cabin noise gets louder. I think that goes up with ambient noise, though, not engine speed.

 

i believe that the radio up is directly linked the the speedometer now that i think about it