2002 Pete 379 Battery/brake issue

I have a 2002 Pete 379 (C15) and recently went to change my batteries and noticed this on both my positive and negative jumpers.

However, the ones that broke weren't just your basic jumpers but had a pigtail coming off it like so


I have no idea where that pigtail goes to or what it is for but I figured it'd be a simple fix. Well local parts places only have the basic jumpers and Rush Peterbilt tells me apparently the ones I have are obsolete and no longer made as they only have the new and improved ones with a more robust and bigger connection... gotta have their $3.5k harness for that tho...

So after searching a few junk yards to no avail I ended up welding the broken contacts back together for a temp fix. This worked as far as starting the truck and it running but now my brake lights do not work. I don't think it's a coincidence. At first if I pushed on the brake pedal really hard or held the trailer brake down they did somewhat work but then that quit and as of now the brake lights flat don't work at all.
The turn and running lights do work, it's only the brakes on both the truck and trailer that are a no go.
I also noticed that if I have the rpms up and on cruise control neither the brakes or the trailer brake no longer cancel the cruise control.

So can anyone tell me where those leads off the battery jumpers go and does my brake light issue sound like a stop light switch gone bad or a relay or both or are these lead/connections perhaps shot from the welding? If I don't respond for a bit it's cuz I have to take a nap before being up early.
Thanks in advance for your time.

 

ah so the weld is likely causing an intermittent connection - I will start there thank you

could the welding to the battery terminal connector end possibly have messed up the deutsch connector as well?

 

Thank you I've been wondering this and was about to call a shop or two to find out. The guy at Rush wasn't much help and didn't know where it went to. Hopefully I've not messed up my ECM with this intermittent connection.

edit before someone asks*
yes I did the welding on the jumper terminal connector disconnected off the truck

 

right that's what I was figuring about the new ones... they have a thicker gauge wire and better connection than the 2002 ones

 

I don't want to buy and install a whole new $3,500 harness just to connect the deutsch connectors from the ecm to the battery cuz a 22 yr old battery terminal connector broke tho lol