aux backup/reverse lights wiring -- a mini howto

[wrooster]

like lots of tacoma owners have found out, the backup (reverse) light situation is pretty dim. i decided to add an aux light for when i'm in reverse, and also make it possible to manually turn it on for temporary campsite illumination or getting my motorcycle into/out of the truck at night after a long day of trail riding.

parts you'll need:
- aux backup light (or two).
- 12V automotive relay with 1/4" faston tabs.
- spool of 16AWG wire.
- three-way clamp on splice connector.
- wire ties.
- electrical tape.
- crimp-on solderless faston connectors, female.

i used a Hella "rubber housing lamp" that someone here on TTORA recommended. it's a nice unit and they are dirt cheap.
hella website link (Hella PN 90610, comes with 55W H3 lamp).

http://www.amazon.com/Hella-H1598602...dp/B000CO7MKK/

mount the light to someplace that it won't get broken off. i mounted mine to the end of the tow bar assembly. i don't rock crawl so i'm not worried about tearing it off where i mounted it, but it is up and out of the way in case i back into a snow bank or something.

note 1: the lens on this light makes a broad flood pattern -- but only if the light is mounted "vertically". if you mount it horizontally, like i did, just push the lamp out of the rubber housing, rotate it 90 degrees, and pop it back in. this keeps the orientation of the flood lens correct.

note 2: while i had the lamp out, i also elected to wire directly to the faston tab inside the light housing, rather than make a splice to the 12" long wire hanging out of the light as delivered. this means one less splice to go bad from getting wet or whatever. it was no problem to take the old wire out, put the new wire through the grommet, and then put a new faston connector on the end. i actually did this when i was all done with running the wire, as i pulled the wire front to back.

the stock wiring, if you try to use it to power the aux lights, will result in very dim aux lights and/or a blown reverse light fuse. so you must use a relay to power the aux reverse light circuit. it is dead simple and no different than using a relay to power your driving lights up front.

the relay i got is from Pep Boys; it's made by "PILOT" but i managed to lose the packaging already so i can't tell you what the Pep Boys PN is. i found it in the bling-bling section near a bunch of neon-colored me-too street light kits. it is sold as a replacement relay for PILOT's full-up kits. here is a look at it:
http://www.pilotautomotive.com/pilot2ap1j.htm
http://www.autobarn.net/pilreprelswi.html

you can of course use any 12V automotive relay for this application, as long as A) the current drawn by your light(s) does not exceed the relay rating, and B) the tabs on the bottom of the relay mate with standard 1/4"-width faston tab connectors. the latter makes it easy to wire to the relay, and you don't need to buy a relay socket. the PILOT brand relay worked well for me.

now the hard part, or what *should* be the hard part -- getting the relay to turn on when the truck is in reverse.

note 3: what i'm about to tell and show you is applicable to my 2002 V6 4WD auto Xtra cab. i believe that most models should be very similar, if not the same, to my setup. or, at least that's what the OEM wiring manuals tell me.

under the driver's seat is a connector block that basically attaches the wiring harness at the front of the truck to the wiring harness to the back of the truck. pretty much everything that goes out back goes through this connector, which is designated "BN7". on pin 22 of BN7 is the circuit which is energized when the truck is in reverse. this is the circuit that drives the OEM backup lights, and this the circuit we are going to use to drive our relay.

your first task... find BN7 on page 1 of:
http://mirror.mmdsi.com/tacoma-manua...emci/027bl.pdf
see the RED wire with BLACK TRACER (R-B) going into and out of pin 22 on BN7? that's your target! you'll note that it is the same for manual or auto.

your second task... find BN7 at the top of page 10 of:
http://mirror.mmdsi.com/tacoma-manua...c/connecto.pdf
the depiction of BN7 on the right is how you will be seeing it in real life. the mated pair of BN7 is mounted to a bracket underneath the driver's seat. with the seat still in place, you will be looking at it from the perspective of the right side diagram, with pin 22 at the lower right hand corner. this is the circuit we need access to.

take off the driver's side door threshold; 4 screws hold it in place. gently pry it up as there are some expanding plastic snaps that hold it into place.

now we need some pics...

threshhold removed:


there is a pinch-clip that holds the rug over the wiring channel that needs to be undone. then, as shown, gently flex the rug up behind the front seat mounting bump.

looking under the rug, you can now see connector BN7, specifically you are looking at the half on the right hand side that i discussed above.


you may need to undo a bit of electrical tape and/or snip a plastic tie wrap to get to the point above. basically you need to put the three-way clamp-on splice connector onto the RED with BLACK TRACER wire which goes into position 22 on BN7 (again, lower right hand corner).


shown in the pics above is a new WHITE WIRE already tapped into the light blue three-way clamp-on splice connector, which in turn straddles the RED with BLACK TRACER wire. these splice connectors simply clamp over the existing wire using a pair of pliers, and take seconds to put on.

that's it, you are tapped into the reverse light circuit! nothing to it, almost like the toyota engineers knew it was coming. put a tie wrap back on if you took it off, and tape over the splice as well. you are done under the seat.

now then...

which way you run the splice wire and where you mount the relay is a matter of personal preference. in my case i already had +12V power in the cubbyhole behind the driver's seat in my Xtracab. this meant, for me, it was a natural place to both run the wire to the aux reverse light from, and place the relay in. hence, my wiring is all done in the cubbyhole. in some cases, it will be easier for you to do the wiring up under the dash, in the engine compartment, or you could even leave the relay under the seat next to BN7. again, it doesn't really matter where you put the relay now that you have access to the reverse light circuit.

so wherever you mount the relay, simply run the reverse light circuit wire to that location. this lead goes to one side of the relay COIL. the other side of the relay COIL goes to ground. again, this is no different from setting up for driving lights.

stop and check here: when you put the truck in reverse, the relay should click.

power for the reverse light(s) can come from your aux fuse block or other source. just be sure the wiring and fuse can handle it. in my case i have an aux fuse block attached to the fender along side the battery; here's a pic from when i was installing it:


it gets it's power directly from the battery:

here's what it looks like all buttoned up:


so i ran power back to the cubbyhole via the channel under the door threshold, and did all of my wiring in there:


you'll need to attach the HOT, FUSED 12Vdc to one side of the relay's switched contacts. the other side of the relay's switched contacts goes out back to the aux light.

the wire back to my aux light passes through the cab via the grommet that is already there (i believe it's only for the trailer wiring):


to reiterate the completed relay connections:
COIL 1: from reverse light circuit.
COIL 2: ground.
CONTACTS 1: FUSED 12V.
CONTACTS 2: AUX LIGHT(S).

completed pics:







good luck.
jim aka the wrooster

edit: fixed links to FSM

[Sgt_Matt]

Looks good !!

[sqwirlytaco]

hey wrooster -- excellent write-up. I have the exact same light... sitting on my refrigerator, for the past 10 months (ya, lotta good it's doing up there). I guess it's time to get off my @ss and wire that baby up.

Question for you -- does that single light provide enough coverage? You mounted the light on the driver's side... do you get enough light on the passenger side?

thanks,
ryan

[wrooster]

Originally Posted by sqwirlytaco

Question for you -- does that single light provide enough coverage? You mounted the light on the driver's side... do you get enough light on the passenger side? thanks, ryan

ryan,
based on just one night's usage -- the single light provides plenty of coverage of both sides. it's a billion percent improvement over the stock setup; simply no comparision at all.

if you mount a single light and find it not-quite-sufficient, just tap the wire at the first light and run it over to a second light. it would take 10 minutes, 5 feet of wire, and another $10 for the second light. but i don't think you'll need it. the H3 bulb in the Hella light is 55W, same as your stock headlight. the lens diffuses the light very well and makes a broad flood pattern.

jim aka the wrooster

[Jeff B]

Great mod and write up!
What kind of fastener did you use to mount the light to the tow bar? Did you tap it?

Thanks- Jeff

[wrooster]

Originally Posted by Jeff B

Great mod and write up!
What kind of fastener did you use to mount the light to the tow bar? Did you tap it?
Thanks- Jeff

jeff,
yes, i tapped a hole into the end of the tow bar end plate using a 5/16"-18 NC tap, and then attached the light using a 3/4" long stainless hex head bolt that i got from Lowes. a 5/16"-18 tap requires a 1/4" tap drill, which makes it easy. there is no depth limit to worry about so you can use a normal tap versus needing a bottom tap. i didn't have any tap fluid handy, so i used some BREAK-FREE CLP to lube the tap -- it was no problem to get the tow bar end plate tapped nicely. you can use kerosene when tapping as well.

in case anyone is wondering, i tapped dead center on the centerline of the crosswise box tube. this is the least stressed area and will not impact overall tow bar strength whatsoever.

don't forget to anti-seize the crap out of the bolt and mating light bracket surface before assembly. eventually the bulb will burn out and you'll have to take it apart again. for this reason (see below) i left a few loops of wire above the light assembly so that you can work on lamp replacement once you get the light assembly off.

jim aka the wrooster

[Jeff B]

Thanks Jim.

[wrooster]

bump -- 'cause i backed up my truck last night and this mod rocks.

jim aka the wrooster

[wslytoy]

nice write up, looks like a pretty clean install!

[Interex]

Clean install! Great write-up!

[ShowStop]

I'll be doing the same thing, but I'll also be adding a switch in the cab so I can turn on the lights whenever I want but also allow them to automatically trigger when in reverse.

[wrooster]

Originally Posted by ShowStop

I'll be doing the same thing, but I'll also be adding a switch in the cab so I can turn on the lights whenever I want but also allow them to automatically trigger when in reverse.

just a suggestion for you -- put a 1N4004 diode(*) in series with the OEM reverse light feed to the relay. this will isolate the OEM reverse light circuit from your aux switch, which is going to feed the same terminal on the relay. then, when you activate your aux switch to turn the relay on, it will not backfeed the OEM reverse light circuit. not that the latter is a bad thing, i just don't know how the OEM circuit works and it may not appreciate 12V being fed back into it. the side effect of the isolation is that the normal reverse lights will not come on when you activate your new aux switch.

ps:
i'm doing the same thing as you, just with a little twist. i worried about accidentally leaving the aux backup light on. it would be nice if it went off automatically, wouldn't it?

and so, i just finished (last night) wiring up a 7 minute delay circuit for this application. it's a little PCB with a 555 timer IC and a tiny relay. on the dash i'll have a SPDT momentary switch. hit the switch to "on" and the aux light comes on -- but automatically goes back off after 7 minutes. hit the switch to "off" while the light is on and it shuts off immediately.

if you are wondering why i picked 7 minutes, well, it just happened to work out that way using the spare components that i had laying around.

i'll post pics tonight.

jim aka the wrooster

(*) if you don't have a 1N4004 diode handy, try radio shack. a 1N4001 or 1N4002 will work as well. it's just that the 1N4004 type is damn near indestructable in an automotive application. if you still can't find one, let me know and i'll send you one.

[Dick Foster]

Just just yanked one of the tail light assemblies and mounted the relay in there with a sheet metal screw. I have a seperate wire to feed the aux lights but pick up the power for the relay coil right off of the stock backup light. If you want to turn them on at will, you could add a cockpit switch to the wire mentioned in the write up.

Most of the lights out there use 55 watt H3 bulbs, including the Hella utility lights. That works out to about 5 amps max per light. Most common automotive relays are rated for 30 amp loads so one relay is plenty good if used for two lights and should last a long time .

BTW if you go off road, you might want to reconsider that location. If I mounted there, they would last about all of 5 minutes after I got on the trail.

[Brandon]

where'd you get that aux. fuse block? i have one like that in my car and can't find another anywhere.

[wrooster]

Originally Posted by Brandon

where'd you get that aux. fuse block? i have one like that in my car and can't find another anywhere.

http://www.rallylights.com/hella/Rel...Fuse_Boxes.asp

PN HL62940 -- Hella Splash Proof 8 Gang ATC Fuse Box, Spade Side Connectors.



what i *don't* like about this fuse block (which i only discovered after i rec'd it) is that the bottom is open to the world. if the fuse blade contacts back out of the plastic (for example, when you are inserting a fuse), the contact can be pushed out of position and touch whatever surface is underneath. that could create a power-to-ground short and it might be on the unfused side. not fun.

all this scared me a bit, as i was planning on mounting it to the metal inside fender next to the battery (see pics above). what i ended up doing was cutting a piece of blank PCB (1/8" thick FR4 epoxy circuit board material) to size and putting it under where i mounted the fuse block (in the pics above and below, the PCB is the yellow/green-ish piece under the fuse block). this provides an insulating barrier and completely removes any possibility of shorts.

moreover, it seems pretty darn stupid of Hella to put an O-ring around the clear plastic top cover but then leave the bottom open to the environment. it may look sexy like that but it's just lipstick on a pig. you can't just goop up the bottom with clear silicone caulking as it will get all over the contacts that the fuses are supposed to mate with. anyway, what i did was carefully cut a couple of pieces of an old heavy duty motorcycle inner tube out and used that as a gasket under the fuse block; hopefully that would help delay entry of water or dirt except in the worst of conditions.

jim aka the wrooster

[wrooster]

Originally Posted by Dick Foster

BTW if you go off road, you might want to reconsider that location. If I mounted there, they would last about all of 5 minutes after I got on the trail.

Originally Posted by wrooster

mount the light to someplace that it won't get broken off. i mounted mine to the end of the tow bar assembly. i don't rock crawl so i'm not worried about tearing it off where i mounted it, but it is up and out of the way in case i back into a snow bank or something.

i mounted the light to improve/help four things:
1) backing up.
2) loading/unloading my bike before dawn or after dark.
3) setting up/tearing down my campsite before dawn or after dark.
4) getting the jetski's onto the trailer after dark.

jim aka the wrooster

[Brandon]

nice thanks for the link!

[ShowStop]

Originally Posted by wrooster

just a suggestion for you -- put a 1N4004 diode(*) in series with the OEM reverse light feed to the relay. this will isolate the OEM reverse light circuit from your aux switch, which is going to feed the same terminal on the relay.

Thanks for the heads up, but I'm already aware of preventing feedback to the OEM circuit. I'm well versed in electronics and have 1N4004 diodes and tons of other components in-stock.

[wrooster]

Originally Posted by ShowStop

I'm well versed in electronics and have 1N4004 diodes and tons of other components in-stock.

very cool... here's a pic of my 7 minute delay in case you want to do something similar. it works perfect and i'd wire it into the truck tonight but it's about 25'F out right now... at the core is a NE555 timer, with the 7 minute monostable mode delay interval set with a trio of 10uF caps and a 10M resistor. the output of the '555 drives the relay directly, with just a series resistor to drop some voltage since i only had a 5V coil PCB-mount relay handy. there is a reverse polarity protection diode up front and a couple of pull-ups for the reset switch circuit, but that's all that is to it. the backside is ugly point-to-point wiring.

jim aka the wrooster

[Dick Foster]

If you're talking to me I picked one up at NAPA.

[Dick Foster]

This guy has a lot of that sort of thing too.

http://www.12voltguy.com

[rplowden]

I'm really bad with pretty much anything electrical and have hardly any know-how when it comes to it also. I'm about to install my CB in my 05 and was wondering if an aux power block as the one you have would be sufficient for wiring a CB to. If so I may add that in as I'm installing the CB for future accessories. Do you have a write up for that somewhere? I searched real quick but didn't find much.

[wrooster]

Originally Posted by rplowden

I'm really bad with pretty much anything electrical and have hardly any know-how when it comes to it also. I'm about to install my CB in my 05 and was wondering if an aux power block as the one you have would be sufficient for wiring a CB to. If so I may add that in as I'm installing the CB for future accessories. Do you have a write up for that somewhere? I searched real quick but didn't find much.

the aux fuse block linked to above and pictured below will work perfectly for wiring a CB to. in fact, the block pictured below powers my 2M ham radio.

one side of the block is wired to the battery, the other side of the block is wired to the loads (like your radio). inserted into the block, in the middle of the circuit, are appropriately sized ATC-type automotive fuses, specific to each load. for example, your CB radio may require a 7.5A fuse; your aux driving lights, a 15A fuse; etc.

just make sure that the wiring and connectors on the battery side of the block can support the TOTAL load. so either use big wire or multiple smaller wires (e.g., multiple 12AWG should support most anything you are trying to power). i chose the latter route -- you can see the way i did it in the lower picture below.

jim aka the wrooster

[cheez]

I have good luck with the Blue Sea fuse blocks clicky and they can be found at West Marine for a decent price.

[mikerox]

Originally Posted by wrooster

very cool... here's a pic of my 7 minute delay in case you want to do something similar. it works perfect and i'd wire it into the truck tonight but it's about 25'F out right now... at the core is a NE555 timer, with the 7 minute monostable mode delay interval set with a trio of 10uF caps and a 10M resistor. the output of the '555 drives the relay directly, with just a series resistor to drop some voltage since i only had a 5V coil PCB-mount relay handy. there is a reverse polarity protection diode up front and a couple of pull-ups for the reset switch circuit, but that's all that is to it. the backside is ugly point-to-point wiring. jim aka the wrooster

wow. now all i need to do is go to school till i understand all of that. this is an awsome write up. i just baought some lights today to put under the truck on the sides and also for a reverse light. i also want some driving lights and fog lights up front and will be getting a cb soon.

i was thinking about the revers circut like you explained and am so glad to have read your post. it saved me the dreaded search tonighyt. i was also thinking about some way to consolidate all the wires since i also have a 7pin trailer harness plus trailer brakes. and that blingin fusu block you got is the ticket. i know what i am shoping for tomorrow.

you didan excelent write up and the pics are awsome.

bythe way. "wrooster" has nothiong to do with all the dirt flyin off the back tire does it?

later
mike

[Dick Foster]

That is about the nicest looking aux fuse block I think I've ever seen. Thanks for that link.

[rplowden]

Awesome, thanks a lot. I may be PMing you soon with a question or two if you don't mind. If you don't hear from me, then I either electricuted myself or it all went fine.

[wrooster]

Originally Posted by mikerox

bythe way. "wrooster" has nothiong to do with all the dirt flyin off the back tire does it? later mike

mike,
yep -- i have a yamaha YZ250F and a WR250F. looking at a KTM 400EXC right now.

jim aka the wrooster

[mikerox]

i have a 426f. love it.

[Dick Foster]

If you're talking to me, feel free.