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post #1 of (permalink) Old 08-13-2008, 12:22 PM Thread Starter
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Arrow Auxiliary backup lights - trailer tow wiring how-to

Well... not really a how-to but thought I'd give advice for anyone else contemplating this add on. Makes for nice night time lighting when backing up. Can add a small switch in the dash to activate the relay under the hood as well for those idiots who drive behind you with hi-beams on.

Here's a pic:

I bought the lights cheap on sale at Princess Auto | Quality Selection Service & Value for $16 bucks. 55w halogen with slight yellow tint lenses. Pulled the lenses off and rippout out the black metal cover over the light bulb for some added glare. Made by Xtreme XT855 model.

The easy way to install these (besides making up custom brackets so they fit so sexy under the bumper) is to wire them into the reverse circuit for the trailer tow harness.

If you look on your 7-pin connector, the centre pin is for trailer reverse lights. They aren't wired direct to the truck's reverse lights, but wired to a relay under the hood which is activated by the truck reverse circuit and separate 20A fuse. This way you don't blow your reverse light circuit if your trailer reverse lights short out or whatever. You need to hook into that center pin wire. It is black with a green stripe. Unplug the trailer tow harness up under the truck so you can work with it on the ground easier - soldering and stuff.

Let me just start first of all that after I installed a Tekonsha Primus electric brake controller for the trailer I tested it on a buddy's trailer prior to me picking up a 26' car hauler today... good thing... no power to the controller. (I have factory tow package & receiver hitch) Look in the manual and guess what... no freakin 30A maxi fuse in the fuse panel under the hood. Ok... pop one in... brake controller works. The tekonsha instructions say the display is blank.... so I thought it was working originally... but there is a tiny dim red LED light that lights everytime you press the brake pedal even with no key in the ignition.

So... back to the reverse lights. Get it all wired up solder and heat shrink into the trailer tow harness. I had to remove the spare tire for easier access (and find out I got the freakin lock on there and no lock code, no key in the glove box - are we having a good day yet??! ) Took me about an hour to get the b*stard off... but that's another thread.

Start it up, put the hand brake on and reverse gear. Hmmm.... no backup lights. ***? Look in the owners manual again. Shows trailer reverse lights towing relay and trailer battery charging relay #38 and #39.... but don't tell me where the hell it is in the fuse box. There are two separate boxes mounted to the underhood fuse box. Each holds two relays. Pop off the covers. The relay box closest to the firewall holds the battery charge relay and reverse lights relay. Nothing in mine so no worky. You can verify you got the right relay plugin box by looking at the wiring loom, same black wire with green stripe going to the back of the truck in there. Go to Ford dealer, cut me a break on price, $23 for two pkg relays Ford Part # FOAZ-14N089-A. BTW, these are identical to typical fog light 30A relays - you just have to bust the screw tab off so they fit under the pop-off cover. Save yourself some cash and go that route.

I also had to relocate the trailer wiring plug under the bumper, somewhat to the left as there wasn't enough room for the light on that side with it in the factory location. The bumper metal is 1/4" thick at least. So I broke off the little tab (once removed from the truck) on the bracket. Drilled a new hole a few inches over. Tapped it for 5/16 bolt. Then fastened it back on with a big washer. Fits great. Nice and flush, just moved over a couple inches.

Anyway, it all works now. But beats me why the truck had the trailer tow package and NO brake controller fuse and no trailer relays.

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2001 F250 4x4 crew lariat 7.3L auto, DP Tuner F5 no-start/valet/20tow/80econo/140aggressive, Adrenaline HPOP, CRUDE diesel performance HPOP lines, NAPC 450series trans w/billet triple disc TC, ISSPRO egt/boost/pyro, foil delete, 6" stainless tip, Magnaflow 17979 4" turbo-back, dieselsite boots & coolant filter kit, boost fooler, 6.0L trans cooler, ported turbo housing, DIY 6637 Tymar, billet grill, line-x bedliner, tint, 08' alum diff cover, clear corners & tails, 20w LED taillight bulbs, Projector headlights w/OPT7 HID kit, 2000w inverter, Tekonsha Primus brake controller, 220A HD alternator, 120w LED light bar up front, 2x18w led spots backup lights, 145USgal tidy tank, superlift 4" kit full springs & bilstein 5125 shocks, 15k 5th wheel hitch, Level8 striker 16x8.5 blk rims, etc.

2009 VW JSW 2.0TDI 6spd Highline. Aftermarket android navi 7" touch head unit, tint, GTI grille and projector fogs.

BioPro190 owner. 40,000L produced 2010-2018.

Last edited by westvandude; 08-29-2009 at 12:33 AM.
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