pdlpsher Posted January 3, 2008 Share Posted January 3, 2008 I found a way to do this very easily without altering or cutting the car's stock wiring. This mod. will supply power to all 12v outlets with or without a key in the ignition. Having this feature is handy for a number of reasons. Say, you may want to charge a cell phone at a camp site. I use portable DVD players for my kids and with this mod. I don't have to reset the DVD player every time I turn off the ignition. Someone on this site has mentioned they wanted to use an electric cooler on long road trips. The list goes on and on. The instruction provided here is specifically for a 2008 Outback. If you have a different model car or model year you will have to identify which fuse(s) powers the 12v outlets. You should read the owner's manual for your car and study the fuse box chart before you begin this mod. Items needed are: 1) 12" of 12 or 14 gauge electrical wire. 2) electrical wire crimper 3) one crimp style electrical connector 4) a multimeter or a DC electrical probe 5) a soldering kit (soldering iron, flux, solder) 6) electrical heat shrink wrap (optional) 7) one mini fuse holder 'add-a-circuit' by Littelfuse (see attached link) http://www.partsexpress.com/pe/showdetl.cfm?Partnumber=071-585 I found the same part at Autozone for $7.50. There are two kinds, one for large fuses and another one for small fuses. Buy the one that's appropriate for your car's fuse box. Procedure: 1) identify the fuses that power your 12v outlets. On my car they are #13 and #20. You also need to identify one fuse that is already constantly 'hot' to use as the power feed for your 12v outlets. On my car I chose the one for the brake lights (#8). 2) take a spare fuse (included in the 'add-a-circuit' package) and cut the fuse in half with a heavy-duty scissor or wire cutter. Remove the plastic portion and try not to damage the fuse's metal pins. The purpose of this step is to harvest the metal pins that you'll need later. Trim and clean up the pins with a knife such that the pins are free of burrs. 3) solder a 6" long 10 or 12 gauge electrical wire to the end of the pin. Repeat step for each fuse you want to make it constant 'hot'. On my car I have a total of three 12v outlets controlled by two fuses. I made two 6" sections. Use heat shrink wrap to cover the exposed area of the pin. 4) using an electrical crimp style connector, connect the wire end of the 'add-a-circuit' to the 6" wire section(s). 5) connect the 'pins' on the 6" wires to the fuse terminals that power the 12v outlets. You need to identify which one of the two fuse terminals lead to the 12v (the other one leads to the battery (ignition switched). To do this you'll need a multimeter or a DC electrical probe. The terminal that leads to the 12v outlet is the one that registers 0v with the ignition on. On my car the correct terminals are 1) top one for #13, and 2) bottom one for #20. 6) connect the other end of 'add-a-circuit' into the brake light fuse terminal (#8 on my car). For this step, please follow the instructions provided by 'add-a-circuit'. You'll also need to add two fuses to 'add-a-circuit', one for the brake light (20 amp on my car) and another for the 12v outlets (10 amp). 7) test the operation of the 12v outlets and you're done! Link to comment Share on other sites More sharing options...
eb50 Posted January 3, 2008 Share Posted January 3, 2008 this is so handy. ill try it on my 05 ob Link to comment Share on other sites More sharing options...
whitetiger Posted January 3, 2008 Share Posted January 3, 2008 I would pick somthing other than the brake light circuit. Link to comment Share on other sites More sharing options...
pdlpsher Posted January 3, 2008 Author Share Posted January 3, 2008 Thanks for your concern but actually there's no worry there. The beauty of 'add-a-circuit' is that it creates a tap in the circuit without altering the original circuit. Notice in the picture that there are two fuses on the 'add-a-circuit'. The original brake light circuit is intact with its own 20amp fuse. The accessories line has its own 10amp fuse which is independent from the brake light's 20amp fuse. I chose the brake light terminal because I know it's constantly 'hot'. I could have put the 'add-a-circuit' on any terminal that is constantly 'hot' without worries, even on the one that supplies power to the engine ECU. Link to comment Share on other sites More sharing options...
2006Specb122 Posted January 5, 2008 Share Posted January 5, 2008 That woudl be my fear... something would drain somewhere and I would be stuck! Some cars are hot....some art... I'm ok... Link to comment Share on other sites More sharing options...
LittleBlueGT Posted January 5, 2008 Share Posted January 5, 2008 I have wired all of my car's power outlet connections to a 12v source for the past 10 or so years. I usually do it when I run my main power supply to the back for my amp. Full tune of 68HTA, KSTech 73 MAF, Racer X FMIC and ID1000s................by the DataLog Mafia!!! Link to comment Share on other sites More sharing options...
Devin Posted January 5, 2008 Share Posted January 5, 2008 subscribe Link to comment Share on other sites More sharing options...
mickeyd2005 Posted January 5, 2008 Share Posted January 5, 2008 The brake light circuit is 20 amps? Link to comment Share on other sites More sharing options...
pdlpsher Posted January 6, 2008 Author Share Posted January 6, 2008 The brake light circuit is 20 amps? Yes. I don't know why. Perhaps Subaru doesn't want the fuse to blow too easily since brake lights are a critical function of the car. Link to comment Share on other sites More sharing options...
Squiden Posted June 14, 2010 Share Posted June 14, 2010 I know this is bumping an old thread, but I'm curious which of the 3 12V plugs were ganged together into one fuse? Was it the console and armrest 12V, or is one ganged with the one in the trunk area? Great write-up! Squid Link to comment Share on other sites More sharing options...
Chulew Posted January 4, 2011 Share Posted January 4, 2011 I have wired all of my car's power outlet connections to a 12v source for the past 10 or so years. I usually do it when I run my main power supply to the back for my amp. So this method would be safe in spite of the post above by 2006Specb122? Link to comment Share on other sites More sharing options...
LittleBlueGT Posted January 4, 2011 Share Posted January 4, 2011 So this method would be safe in spite of the post above by 2006Specb122? Depends if you use it when the car is off and drain the battery. Many older domestic cars have their lighter output always on. If you want to be super careful, then wire in an appropriately sized fuse to the unit. I just use it for cell phone stuff, and other stuff that you would normally charge in a car power outlet. I don't try and blow dry my hair with it. Full tune of 68HTA, KSTech 73 MAF, Racer X FMIC and ID1000s................by the DataLog Mafia!!! Link to comment Share on other sites More sharing options...
Chulew Posted January 4, 2011 Share Posted January 4, 2011 For almost exclusively using it for Bluetooth charging with occasional cell phone charges, and having a 5MT for clutch popping, no worries, thanks! Link to comment Share on other sites More sharing options...
awns729 Posted January 14, 2011 Share Posted January 14, 2011 Procedure: 2) take a spare fuse (included in the 'add-a-circuit' package) and cut the fuse in half with a heavy-duty scissor or wire cutter. Remove the plastic portion and try not to damage the fuse's metal pins. The purpose of this step is to harvest the metal pins that you'll need later. Trim and clean up the pins with a knife such that the pins are free of burrs. Just a note, mine doesn't have a spare fuse. Also from Autozone for $7. 4) using an electrical crimp style connector, connect the wire end of the 'add-a-circuit' to the 6" wire section(s). Any reason this has to be crimped and can't be soldered? 5) connect the 'pins' on the 6" wires to the fuse terminals that power the 12v outlets. You need to identify which one of the two fuse terminals lead to the 12v (the other one leads to the battery (ignition switched). To do this you'll need a multimeter or a DC electrical probe. The terminal that leads to the 12v outlet is the one that registers 0v with the ignition on. On my car the correct terminals are 1) top one for #13, and 2) bottom one for #20. Where did you find ground to measure this? Does the metal bolt in the photo work? (I'm a noob) Thanks Link to comment Share on other sites More sharing options...
Chulew Posted January 14, 2011 Share Posted January 14, 2011 Just a note, mine doesn't have a spare fuse. Also from Autozone for $7. Any reason this has to be crimped and can't be soldered? Where did you find ground to measure this? Does the metal bolt in the photo work? (I'm a noob) Thanks Did mine last night in about 20 minutes. I crimped just because soldering is more work. I used the bold in the door jam. My fusebox looks just like the photo above and with my add-a-fuse installed as in the photo, both leads were 12V. I couldn't get 12V in either of the power sockets and it was cold so I took a chance and just did exactly what was in the photo. Works fine but you may want to check before you do it. For the add-a-fuse fixture, given the layout of the thing I figured it was logical that the 20A brake light fuse would go closest to the fusebox with the 10A on top of it feeding the new lead(s). As far as a spare fuse, I cut the one for the rear power port in two since I would be using the 10A fuse from the front power port in the add-a-fuse circuit. If you are ganging your power together, you'll likely end up with a spare fuse. Link to comment Share on other sites More sharing options...
awns729 Posted January 15, 2011 Share Posted January 15, 2011 For anyone wondering where else you can tap from if you don't wanna use the brake lights, you can use the door locks. I don't think it's really risky to tap into the break lights because the circuits are independent of one another, but if you're messing with fuses why not pick the less important one I suppose. Obviously, door locks are always hot, even with the car off. I tapped into the circuit and popped an extra 10A fuse I had and then connected it to a 12V adapter I found from autozone for $13. So instead of routing add a circuit to the fuse of the built in 12V in the console, I just connected the Add a circuit to the extra 12V adapter i bought from autozone. It comes with two screws to mount it where ever it fits. I grounded by using the screw in the picture in the orginal post. The panel on the left side of the car, right near the fuse box, pops right out with your hand. The 12V adapter wires are routed out of the corner and it just hangs there (for now). OP, this is a really clever way to make an adapter hot. I'll probably get rid of my extra adapter and do it your way when I have time. Link to comment Share on other sites More sharing options...
ehsnils Posted January 15, 2011 Share Posted January 15, 2011 Yes. I don't know why. Perhaps Subaru doesn't want the fuse to blow too easily since brake lights are a critical function of the car. It's so it also can support trailer brake lights. No big deal. As a mod I can see the benefits, but I would have made an arrangement with a switch so I could select if I wanted them permanently on or through the ignition. Link to comment Share on other sites More sharing options...
titoedge Posted June 30, 2011 Share Posted June 30, 2011 I know this is bumping an old thread, but I'm curious which of the 3 12V plugs were ganged together into one fuse? Was it the console and armrest 12V, or is one ganged with the one in the trunk area? Great write-up! Squid the center console and the cargo area are ganged up on plug 13 and the 'cigar lighter' is on plug 20. thanks for the easy mod/write up Link to comment Share on other sites More sharing options...
mestizoracer310 Posted March 21, 2017 Share Posted March 21, 2017 It's so it also can support trailer brake lights. No big deal. As a mod I can see the benefits, but I would have made an arrangement with a switch so I could select if I wanted them permanently on or through the ignition. Did the switch on the 08 prius I had for awhile.... will do on my legacy soon. in our 01 odyssey, the front power outlet is constant hot (so I got a 3 outlet splitter w/ a switch) and the rear outlet is switched voltage. I did add a rear outlet to the legacy too.... might add a switch back there as well, to pick constant hot or when the key is in... Link to comment Share on other sites More sharing options...
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