Tailight wiring question

[seafish]

I have a relatively easy opportunity to add a pair of stop/turn/tail lights to the back my camper shell by using a standard 1157 dual filament bulb in 4" round fixtures that are already installed as extra reverse lights. As I have recently mounted a pair of Hella FF75 fogs in my rear bumper, I do not need the reverse lights anymore, so... .

My question is this--

is the stock tailight wiring sufficient to let me simply solder and shrinkwrap a pigtail to the individual stop/turn/tail wiring at the oem tailight harness and then use the oem circuit to simply light up the additional 27/3 watt bulb on each side, or do I need to use a relay from the pigtail to activate the additonal lights?

I already have extra power available at the rear of the truck to use a relay, but it seems to me that if it is safe to use the existing circuit for the extra 27watts (that's only 2 amps per side ONLY while there is a turn signal or brake light on, the tailight uses the smaller filament at 4 watts, which is practically nothing, right?) then it would be MUCH easier to not have to wire in extra relays for only a 3 amps per side!!

ALL opinions welcome, of course. TIA

 

[HBarlow]

I would guess that you can get away with tying the additional lights to the OEM taillights on an '05. I don't KNOW this is okay but would probably try it myself if it were my situation. Check the capacity of the fuse or breaker for that circuit before you try it to know maximum current draw limits.

I would be leary of doing it on an '06 or later because the lighting on later trucks is computer controlled and delicate.

 

[seafish]

HB, that's good advice. I'll check the fuse labels for the high limit and then do some math. I sure do hope there is enough room for the draw of the added bulbs. I guess that I could always use led lamps for less draw, but I am an "analog" kind of guy, so would prefer to use the filament bulbs.

 

[Road Dog]

I don't have a wiring diagram handy but the the 7-pin connector has a TRAILER circuit for the parking lights (because there can be a lot of them on a trailer) and the LEFT/BRAKE and RIGHT/BRAKE trailer is shared with the truck. If you're adding just a few lights then it shouldn't matter. On my '02 the camper wiring had all 16 marker/parking lights connected to the truck parking lights without incident.

(In Canada a camper sits on the back of a truck and a travel trailer is towed behind. )

 

[Nyoest]

I wouldn't hesitate a bit to tie them into the trailer circuit. Def not the truck side just for safety's sake. If a failure would occur at worst it would blow the trailer circuit, not the truck.

If it were an '06 youd have to do a relay setup so volt draw was consistent.

 

[Hoefler]

I would use the trailer circuit.

 

[PMould]

how about changing the 4 1157s for LED replacements not much draw there.

 

[HBarlow]

how about changing the 4 1157s for LED replacements not much draw there.

If you replace the OEM incandescents with LEDs they draw insufficient current without adding an additional high wattage resistor. Without the resistor on an '05 it will probably cause the turn signal flasher to read the low resistance as a burned out (open) bulb and the turn signals will flash rapidly.

On an '06 or later truck the added resistor is even more important. The lights will not work if replaced with LEDs until a resistor is added to simulate the load of an incandescent bulb.

 

[RDeFayette]

In my own opinion I'd just plug them into the trailer connector.

No issues with the wiring then.

When you have a trailer hooked up just unplug 'em and plug the trailer in, can't see 'em anyway with a trailer in the way.

 

[seafish]

OK... Thanks for all of the opnions/advice.



I DID check the PDM (fuse box) on my 2005 and found these circuits labeled...



#15 50a tail/park lamps

#32 10a right tail lamp

#33 20a trailer park lamps

#34 10a left tail lamp

#46 15a left trailer lights

#47 15a right trailer lights



Obviously #32 and #34 are the truck taillights

and #46 and #47 are the trailer tailights

#33 are trailer running lights/side markers



BUT what is #15, definitely a larger 50 amp fuse, not a relay... looks like this, more or less--

 

[seafish]

In my own opinion I'd just plug them into the trailer connector.

No issues with the wiring then.

When you have a trailer hooked up just unplug 'em and plug the trailer in, can't see 'em anyway with a trailer in the way.

They are actually hight up on the camper shell and I mostly pull a flatbed lumber trailer, so the lights are still visible. Easier for me to solder and shrinkwrap on the wires BEHIND the plug.

 

[seafish]

how about changing the 4 1157s for LED replacements not much draw there.

What I MIGHT do is use led's in the extra lights, thataways the oem incandescent bulbs will keep the computer knowing that they are there (and not defective) and the EXTRA red leds in the new lights won't draw much at all. If I use red Leds, then I will use these--



Amazon.com: 2pcs 1157 Bay15D 18 SMD 5050 LED STOP BRAKE TAIL LIGHT BULBS 12V-RED: Automotive



Unless anyone else will recommend another high quality. , bright, long lasting 360* style led bulb.

 

[RDeFayette]

They are actually hight up on the camper shell and I mostly pull a flatbed lumber trailer, so the lights are still visible. Easier for me to solder and shrinkwrap on the wires BEHIND the plug.

That'll work too. Won't mess with the factory lights either way.

 

[seafish]

Well I don't want to drag this out TOO much longer, though I DO appreciate all the advice and info.



At this point I will solder and shrinkwrap the extra tailights into the trailer circuit and use either incandescent or led lights, depending which looks better and brighter.



Thanks again!!!

 

[RDeFayette]

That's ok we'll drag it out for you! :-laf

 

[seafish]

That's ok we'll drag it out for you! :-laf

And I'll help... . :-laf:-laf


STILL curious if anyone knows what the #15 circuit, with a 50 amp fuse, labeled "tail/park lamps" is used for specifically?? I mean, why would there need to be a separate 50 amp fuse for ALL of the tail and running lights if they are separately fused.

I am thinking that maybe it goes to the TIPM ??

 

[Hoefler]

And I'll help... . :-laf:-laf





STILL curious if anyone knows what the #15 circuit, with a 50 amp fuse, labeled "tail/park lamps" is used for specifically?? I mean, why would there need to be a separate 50 amp fuse for ALL of the tail and running lights if they are separately fused.



I am thinking that maybe it goes to the TIPM ??

Pull it out and see what stops working.

 

[HBarlow]

I haven't looked in years but the 50 amp circuit is probably a trailer wiring circuit.