Merry Christmas!! I need two power sources and being an electrical wiring newbie, I need some help. My first need is for a 12 volt, 10 amp fuse battery (which I assume means "constant"). I was thinking that the motor fuse box would be a good source because there are four available slots and of the two that are occupied, one is for the PCM memory which means the power would be constant...right?

My second need is for a 12 volt, 10 amp fuse, key on hot. I'm guessing that means it's only energized when the key is "on". What would be a good source for this?

Thanks!!

 

Since you never gave any info on what you drive I'll suggest the cigar lighter fuse may be your constant source but test with a test light first. As for IGN source use a test light to find a circuit that turns On with IGN in Run position. I'd try not to use a circuit that controls engine or brake functions as a safety just in case something goes wrong. You can buy add-a-fuse circuit connectors but be aware of the amperage limits and they have to be installed correctly or one blown fuse will also kill the other circuit. Direct Wire Fuse Kit: Auto Electronics : Walmart.com

 

Sorry about that....I drive a 1998 F150 with a 4.2 V6.

 

What equipment are you trying to use for 10 amp circuits?
The cigar outlet is fused for 10 amps max.
There are no switched 10 amp circuits.
You may be in need of custom power feeds to do what you want.
My Ham radio takes more then 10 amps and have dedicated 30 amp filtered power feed into the cab from a fused line direct off the battery.
If you need an ignition controlled switched power, then use a relay controled from a switched source to close through high current source from the battery.
Depending on what your needs are you may or may not need this.
Good luck.

 

Using a relay to provide keyed power is the way to go.
10 amps of battery draw seems to be quite a lot, you might want to consider a switch if possible.

 

I have 3 different power feeds on fused lines directly connected to my battery, a 20A, a 30A and a 40A. I first thought of trying to wire into unused fuse slots, but it looked like more trouble than it was worth, especially fishing the wires into the fuse box and then snaking them from there around the engine compartment to get through the fire wall or back to my truck shell. There is plenty of space for wire bundles to run from the battery to the firewall, and also to run down the firewall and under the cab to wherever else you want to go.
-- I did later need a power feed connected to the ignition switch. The easiest place to find a trigger wire for the relay is right next to the radio, which is fairly easy to pull out of the dashboard along with the supply wires. The OEM power line to the radio is switched on by the ignition circuit. Connect a relay by splicing to this & fish your 12VDC hot wire either through the dash board or up from the floor or console area & under the floor mats. I already had several supply wires inside my cab to connect to an underdash relay.
I have a Brother label printer & carefully labeled my new wires and fuse holders so I could quickly identify which wire and fuse did what. You tend to forget pretty quickly a couple of years after you install new circuits. Or at least I do.

 

What the radio looks like after its pulled out of the dash, wires are still attached.
<iframe src="https://skydrive.live.com/embed?cid=E6418942DC619CB4&resid=E6418942DC619CB4% 213162&authkey=ACvayQuLCKU14LA" frameborder="0" height="320" scrolling="no" width="239"></iframe>
I removed a lot more of the dash than was strictly necessary to pull the radio, but you should be able to clearly see what you are dealing with from the photo.