Aux Switch wiring location

[20Limited3500]

What year is the chassis cab you show in this pic? I ask because my 2020 3500 Limited has these exact same wires in the same location as shown in this pic.
I am wanting to install some flush mounted LED lights into the rear bumper and would like to be able to control them via one of the 6 Aux Switches on the dash. I had originally bought the lights for the 2016 3500 Limited I had but could never locate the wires in the back. I gave up on the idea with that truck. Now that I have the new one, and I've had the rear bumper off already to install a heavier duty hitch, I want to install the lights and finally use them. Definitely will be following this for as much info that I can ascertain.

I am currently working on a YouTube video and PDF document explaining the AUX wiring system. I have been holding off on publishing the video or document because I was hoping to find the blunt wires so I could include them in the video. Please post pictures when you can.

Here is a picture of the blunt wire location on a chassis cab which is exactly where the upfitter wiring diagram says it should be.


View attachment 4770

 

[Brutal_HO]

What year is the chassis cab you show in this pic? I ask because my 2020 3500 Limited has these exact same wires in the same location as shown in this pic.
I am wanting to install some flush mounted LED lights into the rear bumper and would like to be able to control them via one of the 6 Aux Switches on the dash. I had originally bought the lights for the 2016 3500 Limited I had but could never locate the wires in the back. I gave up on the idea with that truck. Now that I have the new one, and I've had the rear bumper off already to install a heavier duty hitch, I want to install the lights and finally use them. Definitely will be following this for as much info that I can ascertain.

Thats not a chasis cab photo, thats my truck and my hand. lol

I misspoke. Not on the driver's side. They are on top of the rear tire, passenger side. Here's pic of the two in question plus one other that I don't know what it is used for.

View attachment 4799

Those two blunt cut wires are BAT+ and IGN and come from the AUX PDC. You have to plug in the Light Grey jumper harness that came in the upfitter wiring bag into the connector under the dash to bring power to them in the rear. In that under dash jumper is an additional blunt cut wire that is on a "pass thru" circuit (G425). You could repin the jumper and wires to carry that pass thru circuit to the rear on one of the others. Then under the hood, you loop one of the aux switches to the pass through pin (it's on the same set of Aux plugs.)

I suppose you could also get into the AUX PDC at pin 45 (A500) and use that line in one of the aux positions if you wanted to use the pass thru under the dash (that's what I'm using it for.)

Study the body builder schematic and you'll see it all.

@thestuarts is putting together a doc that details everything we've been kicking around in the different threads regarding this wiring but hasn't published it yet.

 

[thestuarts]

@thestuarts is putting together a doc that details everything we've been kicking around in the different threads regarding this wiring but hasn't published it yet.

I have held off on publishing the AUX switches doc because I was hoping to find the location of the blunt wires on the 2019 trucks so I could include that in the PDF. If nobody finds the 2019 wires by this weekend, I will go ahead and publish the doc.

 

[Gondul]

I'd be happy to go look... any suggested locations?

 

[thestuarts]

I'd be happy to go look... any suggested locations?

The upfitter wiring diagram indicates the red/white and pink/orange blunt wires should be at location F below which is vaguely described as "Vehicle Wiring, Blunt Cut (with Heat Shrink) Rear of Frame."



However, here are pictures of the wires on a 2020 model year truck. The wires aren't actually located where the upfitter diagram indicates they should be located. They are actually located near the spare tire lowering mechanism, so you may have to remove the spare tire to get a good view of all the wires.

Here is another picture of the wires on a 2020 truck.

 

[Brutal_HO]

The upfitter wiring diagram indicates the red/white and pink/orange blunt wires should be at location F below which is vaguely described as "Vehicle Wiring, Blunt Cut (with Heat Shrink) Rear of Frame."

View attachment 4817

However, here are pictures of the wires on a 2020 model year truck. The wires aren't actually located where the upfitter diagram indicates they should be located. They are actually located near the spare tire lowering mechanism, so you may have to remove the spare tire to get a good view of all the wires.

Here is another picture of the wires on a 2020 truck.

Considering M is the stop light blunt cut and someone has already posted a pic showing them pretty close to each other, F should be somewhere on the passenger side of midship.

 

[Gondul]

I'll drop the spare sometime this weekend and see what I can find for you.

 

[thestuarts]

Considering M is the stop light blunt cut and someone has already posted a pic showing them pretty close to each other, F should be somewhere on the passenger side of midship.

I just spent another hour under the truck using my Progressive Industries toner with brand-new batteries. I connected the toner to the wire on pin #4 of the AUX jumper which is the pink/orange wire that should go to the back of the truck. The toner can't find the wire anywhere at the back of the truck. I followed the main wiring harness from the back of the truck all the way to the cab without any tone. When I get near the cab I can hear the tone, but I can't figure out where the wire terminates. At this point, I'm giving up on locating the BATTERY and RUN wires at the back of my 2019.

 

[Brutal_HO]

I just spent another hour under the truck using my Progressive Industries toner with brand-new batteries. I connected the toner to the wire on pin #4 of the AUX jumper which is the pink/orange wire that should go to the back of the truck. The toner can't find the wire anywhere at the back of the truck. I followed the main wiring harness from the back of the truck all the way to the cab without any tone. When I get near the cab I can hear the tone, but I can't figure out where the wire terminates. At this point, I'm giving up on locating the BATTERY and RUN wires at the back of my 2019.

well $hit, after all that work, that sucks.

 

[thestuarts]

well $hit, after all that work, that sucks.

I am going to retest with the toner today. I installed an inline fuse to the rear of the truck (like @brutal recommended to me), but I forgot I never installed a freakin' fuse in the fuse holder. I suspect my test was invalid yesterday.

Momma tried to fix my stupid, but she said I inherited it from my dad.

 

[John Jensen]

That's one of those things you hate to admit - we've all done it - know how you feel - good luck on retest

 

[thestuarts]

I figured out the problem with the 2019 trucks (at least mine). The BATTERY and RUN power lines terminate at a large connector that is above the spare tire. It should be as easy as plugging in the right size pigtails into the large connector (or cut the wires or de-pin them from the connector).
EDIT: I don't recommend de-pinning the wires from the connector because that will enable water to get into the connector.
EDIT: The colors may be misleading in the photo. The larger RUN wire is pink with an orange stripe. The smaller BATTERY wire is red with a white stripe.

Interestingly, the BATTERY wire is a much smaller wire than the RUN wire. I am curious if this is the same for the 2020 trucks.

 

[John Jensen]

That's great that you solved the 2019 mystery. I cannot say about the connector battery & run wire sizes. I don't even see that connector on mt 2020 but I have not dropped the spare to see further. I can say the blunt ends on my 2020 look the same size. Again, I don't know if the blunt ends come from a connector or are simply wires in the harness that have been pulled out of the sheath and blunted.

 

[thestuarts]

That's great that you solved the 2019 mystery. I cannot say about the connector battery & run wire sizes. I don't even see that connector on mt 2020 but I have not dropped the spare to see further. I can say the blunt ends on my 2020 look the same size. Again, I don't know if the blunt ends come from a connector or are simply wires in the harness that have been pulled out of the sheath and blunted.

You would need to drop the spare tire to see this connector. It is attached to the top of the tire lowering mechanism bracket. Thanks for confirming the blunt wires are the same size!

This isn't a compelling reason for me to get rid of my 2019 truck, but this is yet another example that makes me wonder if the 2019's were released before they were ready. The TTPMS system is another example indicative of a premature release.

 

[John Jensen]

I may have misspoken. When I blow up my pic (post #18) the wires don't appear to be the same size. And now it is further confusing me because the blunt end wire colors do not match your post of the connector. Are you sure that large red wire is the run wire?

 

[thestuarts]

I may have misspoken. When I blow up my pic (post #18) the wires don't appear to be the same size. And now it is further confusing me because the blunt end wire colors do not match your post of the connector. Are you sure that large red wire is the run wire?

I looked at your photo again. I agree, your red/white BATTERY wire does seem to be smaller than your pink/orange RUN wire.

The colors may be misleading in my photo because the large wire is not red. The large wire is pink/orange and is connected to the RUN wire that feeds into the gray AUX connector in the cab. The smaller wire is red/white and is connected to the BATTERY wire that feeds into the gray AUX connector in the cab. You have to plug the gray AUX jumper into the gray AUX connector to get RUN/BATTERY power to the rear of the truck.

 

[thestuarts]

For 2019 owners, the AUX pigtails that came with the AUX wiring kit fit perfectly in the large connector. To insert a pigtail, you have to release a locking mechanism inside the large connector. The pigtail has a square cutout in the tip that must face the center of the connector when inserting the pigtail.

Finally I have AUX RUN power at the rear of the truck!

The red/white battery wire is too small, IMO. If I ever need battery power at the rear of the truck, I will just run a new wire from the main fusebox or the PDC.

 

[Brutal_HO]

For 2019 owners, the AUX pigtails that came with the AUX wiring kit fit perfectly in the large connector. To insert a pigtail, you have to release a locking mechanism inside the large connector. The pigtail has a square cutout in the tip that must face the center of the connector when inserting the pigtail.

Finally I have AUX RUN power at the rear of the truck!

The red/white battery wire is too small, IMO. If I ever need battery power at the rear of the truck, I will just run a new wire from the main fusebox or the PDC.

View attachment 4873

View attachment 4874

I'm glad you got that as I was going to suggest it after seeing the earlier post.

Yay!

 

[Brutal_HO]

I figured out the problem with the 2019 trucks (at least mine). The BATTERY and RUN power lines terminate at a large connector that is above the spare tire. It should be as easy as plugging in the right size pigtails into the large connector (or cut the wires or de-pin them from the connector).
EDIT: I don't recommend de-pinning the wires from the connector because that will enable water to get into the connector.
EDIT: The colors may be misleading in the photo. The larger RUN wire is pink with an orange stripe. The smaller BATTERY wire is red with a white stripe.

Interestingly, the BATTERY wire is a much smaller wire than the RUN wire. I am curious if this is the same for the 2020 trucks.

View attachment 4870

View attachment 4871

Glad my monitor is calibrated. Those colors look exactly as described on the computer.

P.S. Nice try blaming me for your lack of electrical genetics.

 

[Nifty07]

Would you be kind enough to post the pinout of the large connector please.