Finally getting around to doing some modifications to my HD

8ball_99

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Hey guy, Finally getting around to doing a few things to my truck. Been waiting for parts to get my 2nd battery in. Working on that now then plan on doing my stereo, dash cam, ect. I also got my upfitter switches wired up. I connected those to the AUX battery vs running them of the starting battery. I'll probably just post a few pictures and what not on this thread as I go.

I do have a question though, Maybe someone on here will have some insight. My original plan for my AUX battery was to trigger the isolator after the engine was running. Best I can tell the stock circuit to do this is not present in my truck. If it is I sure can't find it. I found a circuit on the BCM marked as Auxiliary battery relay control on the electrical body builder manual for the truck. But after testing it, that circuit does nothing. So, I'm assuming my truck is missing some of the wiring or some other component somewhere. Not a huge deal and for now I just connected my isolator to one of the upfitter switches that's set to come on with the ignition. My isolator is 500 amp rated and the way it's wired it shouldn't matter if the starter pulls across it.

My question is though would anyone know where on the BCM to get a signal once the engine is actually running? I would like to have the isolator only kick on after the engine starts. With how I have it now, it powers up anytime you turn the key on. Course with the switch I can just turn it off. Which keeps the batteries separated even when the key is on. Might not matter, But in my mind if I pull my aux battery down and go to start my truck. As soon as I hit the start button, the batteries will be connected. Which would cause the aux battery to pull on the starting battery the same time the starter is also. Sorta of the point for the AUX battery is to be able to pull it down with out effecting starting the truck lol. Yes I can hit the upfitter switch and prevent that. But that adds another step. The only advantage I do see to this arrangement is if my starting battery is low for what ever reason (failed update maybe. lol) The AUX battery would act like a jumper. To me though ideally the two batteries would normally stay separated until the engine is running. I don't know maybe I'm over thinking it. What do you guys think. Should I bother with it, or just leave it like it is?

Here is a couple picture's of the battery install so far.
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IDK, cause I haven't dug into the electronics much other than Amp steps install.

If I was you, I would wander down to the dealer and see if you could talk to one of their techs. They may have some knowledge on how the BCM is working or at.least be able to look it up.

I know the thing I get most concerned with messing with the main harnesses, BCM, and ECM is frying something and ending up with a high $ repair.

I prefer to work right off battery or separate fuse relay block. I had to splice wires into BCM for Amp steps and the wiring and connections both seemed cheap as hell. Now I've figured out when I pull the AMP computer from OBD port it throws a shit ton of network codes and stores them as non active codes. Doesn't seem to affect anything, but I worry how that will be interpreted if I need warranty repairs on electronics.
 
IDK, cause I haven't dug into the electronics much other than Amp steps install.

If I was you, I would wander down to the dealer and see if you could talk to one of their techs. They may have some knowledge on how the BCM is working or at.least be able to look it up.

I know the thing I get most concerned with messing with the main harnesses, BCM, and ECM is frying something and ending up with a high $ repair.

I prefer to work right off battery or separate fuse relay block. I had to splice wires into BCM for Amp steps and the wiring and connections both seemed cheap as hell. Now I've figured out when I pull the AMP computer from OBD port it throws a shit ton of network codes and stores them as non active codes. Doesn't seem to affect anything, but I worry how that will be interpreted if I need warranty repairs on electronics.

Well I said BCM, cause that's where that original control circuit I had planned to use was. It actually could be from anywhere under the hood also. But yeah definitely not something to be poking around in willy-nilly. I actually was just going off electrical schematics for the 24 HDs. I would never just probe random wires in there.
The way I wired I have a small relay under the hood that triggers the larger isolator relay. So where ever I get the signal from would have very little draw. Just enough to trigger the small relay. I'm sure there is probably a hvac circuit or something somewhere that throws 12v once the engine has started. It's just a matter of knowing where to look. It will work as is. A smart isolator won't work on these trucks because of the "smart" charging system. No biggie, I can always come back to it later.

I just needed the auxiliary battery in to move on to the other stuff. About to do the dash cam then start on the stereo now. Onboard air will be after that!
 
Got a little more done, most if the wiring is done. 12v outlet in the console. Dash camera is in and I almost got the stereo done. Still have a few more connections to make and the I need to change the door speakers.

I made a harness with some 12pin plugs to make my connections to the factory bose amp. This way too, if remove the stereo later. I can just plug the bose harness back together again.
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Got my amps in and everything hooked up finally! Good to have my stereo back. Been missing it driving around with the stock bose past few weeks. Didn't really take many pictures as I was just trying to get everything done. Did take one of the amp rack before it was completely wired up though.
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You guys are daring😎

I am even hesitant to remove the A pillar panel to add dash cam wiring and mess with the fuse box on passenger side 😁
 
Figured I'd post this. I did the same thing on my 1500. I took this bracket off when I traded. Happy to report it fit the 2500 NP. I didn't have to modify it all. Bolted right up to the handle bolts. Added a lock actuator so my bed cover locks when I lock the truck and unlocks when I hit the button twice to unlock all the doors. For anyone interested in what wire colors are for the rear lock actuators there is a picture of them and where I tapped into them.
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Put my onboard air on this weekend. Was a bit of a PITA. Sorta expected to be easier on the HD then the 1500. But space is actually a little more limited under these. Just the way everything is laid out and with the larger fuel tank. I had to split my compressors up. One on each side. Also was no where under the truck to mount my train horns. So I ended up putting them behind the grill up front.

lol, Side note, taking the grill of on these trucks is a bit involved. Took me a min to figure it out. Surprised me you have to pull the fender flares halfway off and pull the front painted section off to get to the bolts holding the grill on. Pictures aren't great, but they show the basic layout of everything.

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Put my onboard air on this weekend. Was a bit of a PITA. Sorta expected to be easier on the HD then the 1500. But space is actually a little more limited under these. Just the way everything is laid out and with the larger fuel tank. I had to split my compressors up. One on each side. Also was no where under the truck to mount my train horns. So I ended up putting them behind the grill up front.

lol, Side note, taking the grill of on these trucks is a bit involved. Took me a min to figure it out. Surprised me you have to pull the fender flares halfway off and pull the front painted section off to get to the bolts holding the grill on. Pictures aren't great, but they show the basic layout of everything.

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frickin bad ass train horns....or are they cargo ship??? NICE setup....crisp and ckean looking.
 
frickin bad ass train horns....or are they cargo ship??? NICE setup....crisp and ckean looking.
Thanks, They are train horns. 4 horn Shockers from hornblasters. I had them on my 1500 before. They sound great, just like a train. I made a mount for them for the last truck. Was hoping to reuse it. But it just wouldn't work anywhere on the HD.

This is how they were mounted on the 1500.
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Thanks, They are train horns. 4 horn Shockers from hornblasters. I had them on my 1500 before. They sound great, just like a train. I made a mountain for them for the last truck. Was hoping to reuse it. But it just wouldn't work anywhere on the HD.

This is how they were mounted on the 1500.
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props again on clean install.
 
Yep that was what is was like pulling the lower facia on the 1500. There are so many bits and pieces that make up the front clip it ends up being a long and tedious process.

Always good to see photos like this in case you need to get in there. Thanks for sharing.
 
Yep that was what is was like pulling the lower facia on the 1500. There are so many bits and pieces that make up the front clip it ends up being a long and tedious process.

Always good to see photos like this in case you need to get in there. Thanks for sharing.

It's probably no big deal if you know what you're doing, i didn't lol. I put it back together in like 5 mins. But getting it apart for the first time had me guessing some. The clips on the fender flares also wanted to stay in the fenders. So I had to go back pull each clip and reinstall them in the flares.
 
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@8ball_99 super awesome. Do post video of the sound. I am sure truck drivers will also love it. 😁

Btw, where did you mount your air compressor. I see air tanks though.
If I have to do this personally, it will be forever under construction or EOL of truck😂
 
It's probably no big deal if you know what you're doing, i didn't lol. I put it back together in like 5 mins. But getting it apart for the first time had me guessing some. The clips on the fender flares also wanted to stay in the fenders. So I had to go back pull each clip and reinstall them in the flares.
Yeah, it's always 1/2 the time the second go round!
 
@8ball_99 super awesome. Do post video of the sound. I am sure truck drivers will also love it. 😁

Btw, where did you mount your air compressor. I see air tanks though.
If I have to do this personally, it will be forever under construction or EOL of truck😂
It's not a great photo, but both compressors are mounted basically behind the bed step on the frame. Just infront of the rear springs. Nice open spot on the frame that's slightly elevated just behind the cab mount. I put one on each side. I couldn't really find anywhere to mount both compressors next to each other like i did on the 1500. I had two air tanks anyway, so worked out in my case. With a single tank, probably be best to run one compressor. The two tanks are connected with a air line between them. So they act like one larger tank fed by two compressors.

The cross member under the truck is hollow and open on each end. So the line connecting the two tanks runs through it. Which I thought was cool. Made it easy to run a airline across and it's fully protected in a steel tube.
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For anyone interested in some version of this here is the main parts.
3 gallon air tank
5 gallon air tank
Compressors
Compressor mounts
Air line
Pressure regulator

These Bulkhead fittings are pretty slick for mounting the couplers through the bumper steps. I just used standard push to connect couplers in the bumper to attach air hoses to. Other than that just various fittings and some wire to connect everything.
Nice info. I saw Viair but thought they might be additional tanks.

Looks like links are not working.
 

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