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  1. My son just checked the truck and the battery connection to the lug I was asking about in the previous post-it is dead - no power going to it. So Hmmmmm....What is somewhere in the truck that has no power and then why is it there?
  2. Hey @Rozz522, I ordered part number 84663447 - J Block Auxiliary Battery, 84471670 Junction Block Cover I still have to get under the hood (I am away till next week) and clarify a few things: "Supposedly" under the battery mount could be the connector X136 which would then allow you to run to the relay KR81 (Auxiliary Battery Relay 1) from this relay you go to the KR79 (Auxiliary Battery Relay 2) that supposedly comes included in the J Block Auxiliary Battery? I ordered the 220 amp alternator so I have to wait for parts to arrive. I have some questions still to answer about the fuse block X50D as I have a wire coming off it that is not identified in the Upfitter wire diagrams. I plan to make the battery hold down parts as they are expensive for what they are. A new positive cable just has a pig tail off the end connection so I will also make that verses buying a new cable - same with the ground. I downloaded a pic from this site where someone was discussing the connections. This is what it would/should end up like: Trying to figure out where the unfused terminal above the blue connection goes to? It is not on any drawings other than the Diesel engine where it would go to an auxiliary heater? I have seen YOUTUBE videos and it is not on some of the trucks?? Maybe it runs to the Invertor for the 120 outlets?? From the Upfitter site material the Auxiliary battery will charge when you are in tow/haul mode and pulling a trailer, or I assume in that mode. Still figuring out if that is the whole gist of it?
  3. @Gr8FrozenNorth : did you ever complete this operation of adding the auxiliary battery and increasing the alternator capacity? I just purchased a 2021 2500HD LT and they "forgot" to install the package or couldn't due to missing parts. Anyway I have the parts ordered and a new 220 volt alternator on the way and will be doing this mod in a few weeks when everything arrives. My truck arrived with the 170 Amp Alternator but has a 250 amp fuse for the alternator on the main battery. For a 170 amp alternator this would normally be a 175 amp fuse. For some reason my fuse block is from a 1500 Diesel with a 220 Alternator - for me, that is a good thing I purchased the " J Block Auxiliary Battery" 84663447 - this part comes with a 30 amp fuse, a 100 amp fuse and a 175 amp fuse. The 100 amp fuse is connected to an isolator relay all as one assembly. The cover is Junction Block Cover 84471670 I am re-using the cable from the main battery positive to the terminal on the X50D (175 amp) it runs from the main battery over to the X50A Fuse Block (as per normal) and then a short pigtail will run from that connection to the 100 AMP fuse on the auxiliary battery J Block (X50E). this is the fuse attached to the isolator. The isolator is supposed to be powered from a secondary relay that wires into a connector X136. I have to find all that on the truck first but I am away on business so it will take a bit. right now I am still in research mode but it looks like that is pretty much it other than connecting the trailer 30 supply power wire up. From reading the battery relay will energize if you switch to tow/haul mode and it will charge the aux battery. maybe someone with the factory install would have more intel. I will post pictures once things get underway.
  4. What I think is correct the the 2500HD LT for the Aux Battery circuit: On this drawing though, F79UA 10A is misnamed and actually called the AUX BATT/SCRPM in other locations of the electrical schematics
  5. So here is the crazy thing: On my truck: 2021 2500HD 6.6 gas LT I requested the 220 amp alternator and aux battery - It didn't come that way - no aux battery and a 170 alternator BUT: My fuse panel on top of the regular battery is NOT the correct one for the set up as fitted (according to GM parts) my fuse block is part number 84646133 this is a fuse block from a 1500 diesel with a 220 amp alternator. So my fuse block (X50D) has the following F1 - 250 Amp connected to 170 Amp ALT, F2 - 175 Amp connected to Fuse Bock X50A F3 - 400 Amp connected to Starter Motor The next 2 fuses are 60 amp and run to the interior fuse panels and then I have a 1 more wire in the supposedly F4 position that is not fused and is a decent size wire. No idea where this runs to and does not jive with any wiring diagrams on the GMUpfitters. From the wire diagrams it "should" be easy enough to install the GM Fuse Block Auxiliary Battery 84663447. The wire from F2 175 amp would run to the 100 amp fuse in the X50E aux battery block and then back to the X50A fuse panel. The Auxiliary Fuse Block may already have the battery isolation relay (KR79) that is supposedly controlled with a simple connection to the body control module. (connector x136). This would be a very simple install and follows the jist of the parts diagrams for the auxiliary installation. The GMUpfitters electrical seems to be riddled with mistakes or errors , probably created by the lack of parts during covid - my truck is supposed to have the main battery fuse block X50D as part number 84646132, which I suspect has a lower rated 200 Amp F1 Fuse, not the 250 - it will make a 220 alt upgrade a lot easier though. I have an after market isolator, but for simplicity and looks under the hood it would be just as easy to purchase the required X50E OEM part. I tried to load the wire diagram and pics but exceeded the limit and then it won't let me try again...
  6. For you guys installing this, I have a 2021 2500 HD and things look just a bit different on the electrical side and I have a question/favor to ask if any of you have the second battery: Can you post a picture of the open fuse box on the 2nd Battery? The GM part # is 84663447 and I cannot get a clear answer whether the box contains the relays and fuses or it is just bare and you need to add. From the cost it seems it should have the guts. Also, I went to order the kit 84942073 for the 9L7 ( upfitter switches) and it seemed way to cheap - like it was $65 ? that doesn't sound like a "complete" install kit so I am awaiting word back on that. I would like to install the upfitters with the 2nd battery for trailering and I work out of my truck bed at times so I would add some lights, radio etc I had requested a few options when I sent in my build but I guess some of the wiring was not done due to some harness availability out of Mexico? Thanks to anyone who can help me out - great write up and contributions all around
  7. The GM Upfitters site has the instructions I do believe. There is a hole to drill for sure and it does provide a guide to the connector. for some reason I cannot get to the site right now due to a privacy thing from google
  8. Is there anyone out there that can take a couple pictures of the second battery installation? Perhaps the cover off the fuse block and along the wire run? I ordered my truck to come with the second battery and they did not put this in, I instead got the powered lift and drop tailgate. This feature is not available (don't think so?) on your typical LT model so it was a bit of a surprise. The added battery is so I can power things in the back cap while I work out of it when doing on site carpentry type things. I have been through the GM Upfitters and the auxiliary battery is not yet a bulletin, also their electrical schematic manual has some mistakes - or there are some differences in my trucks wiring from what they have listed. The fuse block (X50E) that connects to the positive on the aux battery is about $165.00 the guy at the parts counter doesn't have one in stock and with covid you cannot go and look anyway - I want to know if the isolation relay and control relay are actually included in this part (GM 84663447). If not, $165.00 is ridiculous for just a piece of ABS plastic. There is no listing for the relay on the parts page so that is also confusing. The tray is in place already and the wire harness looks like it is just a short pigtail added to the main connection back to the X50A fuse box - just do not know where the isolation relay power comes from (supposed to be connector X136) so will have to find that. Any pictures would be great....thanks
  9. That is the problem, you need to have a z71 or higher package+ to get that option. I have an LT and could not get the option unless I have the rear cargo camera - useless for me as I have a truck cap - not worth paying for. GM sorta shooting themselves in the foot as this would be a sweet "standard" edition to the LT plus packages
  10. Looking for the same - will post if I can get some information
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