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Hey all, I've done a lot of reading on this topic in this thread and I think I have it mostly down. This will be on a Leer 100XQ.
However, I'd like to run my idea by anyone who has done this and willing to listen / give any input.
Brake light - This one is pretty cut and dry. T into the green wire already at the back of the truck and run the wiring up through the bed post on the driver's side it looks like. Question: Will and inline fuse be necessary? If so, what amp do you suggest.
Dome light - Either run a new lead off the positive battery post, or T off the black 12V wire doing to the cigarette lighter. This will be ran to a switch. Again, would an inline fuse be necessary, and if so, what amp is preferable?
I am already working on running some LED wiring through the firewall, so I will have a path already created.
I wouldn't run anything directly off of the battery post.
For the dome light, are you going to be using it separately from the interior cab lights? If not why don't you tie into the wiring for the cab light? put a 5 or 10amp inline fuse on it and be done, that is if you don't need it to be a separate switch.
Brake light, If you're tying into the brake light at the rear, the only reason to fuse it is so the bulb in the Leer top doesn't blow if there's a surge or short in the rest of the system, so again, a 5 or 10 amp inline fuse would probably do it, I don't know what the main fuse is for brake lights, but if it's a 20 amp then I'd probably match it to that.
I wouldn't run anything directly off of the battery post.
For the dome light, are you going to be using it separately from the interior cab lights? If not why don't you tie into the wiring for the cab light? put a 5 or 10amp inline fuse on it and be done, that is if you don't need it to be a separate switch.
Brake light, If you're tying into the brake light at the rear, the only reason to fuse it is so the bulb in the Leer top doesn't blow if there's a surge or short in the rest of the system, so again, a 5 or 10 amp inline fuse would probably do it, I don't know what the main fuse is for brake lights, but if it's a 20 amp then I'd probably match it to that.
Thanks Mike. Strangely enough, functioning the light in the truck would be preferable. I will be under the dash already, it's not big thing to run a wire off a 12V constant.
Just throwing this back out there again, something I have used for camper shell wiring. This would save you from needing to run another wire to the back since the brake wire is already back there. If you want to operate the dome with the in-cab lights you could run a small gauge signal wire to the back with a relay off the aux battery.
I also like having fuses on everything. It is cheap insurance. https://www.ford-trucks.com/forums/1...l#post16068202
Originally Posted by Sam I Am
On my 1997 F150 I did not run a separate power wire back for the cap dome light.
To do this, the brake wiring stays like you have it in the diagram (but connected), and you use it to charge a small battery that powers the dome light.
I tee'd off the green CHMSL brake wire and ran it through a diode to the hot side of a small sealed 12V battery out of an uninterruptible power supply (UPS). Wire the dome light to the battery and it doesn't matter if you forget and leave the light on all night, it won't run down the main vehicle battery.
Each time you step on the brake the little battery gets some charge.
And the diode keeps the battery from back feeding the brake light circuit so the brake light on the cap doesn't stay on all the time
This worked great, I used it for a couple of years on the same UPS battery. I even left it on all night on purpose just to see how long it would run and it was still shining just as bright in the morning.
This is also a handy way to get a 12V power source at the back of the truck to run low draw stuff like a phone or laptop charger. Just be sure to put inline fuses on everything.
FYI, anyone else looking to add a cap, at the factory Ford leaves the green brake wire hanging out of the harness at the back of the truck.
I believe it is solid green, and mine have all been labelled like the picture shows (Center High Mounted Stop Light). It is blunt cut with nothing connected to it from the factory so there isn't really anything to "T" into, you just splice into it to run the brake light to the cap. They are usually sticking out in plain sight but some are tucked into the plastic harness cover.
And you can get the ground from the common white wire that bolts to the frame next to the spare, or make your own connection to the frame. If you use the one that is already there, I recommend unbolting it from the frame and cleaning it thoroughly to ensure a good connection that will last.
If you are going to solder it and do it right it doesn't really matter where you attach your ground to the white wire, but I prefer to run a new dedicated ground wire to the same ground point and clean them all at the same time. I mention this because I really don't like the Scotch Lock type quick splice connectors. And I always prefer to not disturb a vehicle's original wiring any more than necessary.
I believe it is solid green, and mine have all been labelled like the picture shows (Center High Mounted Stop Light). It is blunt cut with nothing connected to it from the factory so there isn't really anything to "T" into, you just splice into it to run the brake light to the cap. They are usually sticking out in plain sight but some are tucked into the plastic harness cover.
And you can get the ground from the common white wire that bolts to the frame next to the spare, or make your own connection to the frame. If you use the one that is already there, I recommend unbolting it from the frame and cleaning it thoroughly to ensure a good connection that will last.
If you are going to solder it and do it right it doesn't really matter where you attach your ground to the white wire, but I prefer to run a new dedicated ground wire to the same ground point and clean them all at the same time. I mention this because I really don't like the Scotch Lock type quick splice connectors. And I always prefer to not disturb a vehicle's original wiring any more than necessary.
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