Help with electrical on 2000 international 9400i

I keep blowing fuse on my heater control module ign feed... it's the 9d position in my fuse panel... I'm unsure why it started but here's all I've done to try an find / fix problem...

I had just changed some tail lights on my truck and that's about the time this started happening. I cut and disconnected tail lights thinking this was the cause but it still popped another fuse. Next I looked at all wires following them to my batteries. I had 1 battery with the ground terminal melted so I switched batteries out.. to no avail as fuse still popped. Next I disconnected my heater fan the switch module and anything to do with a/c or heat in my truck I even pulled out my a/c compressor as it is bad and time for new one yet I'm still popping a fuse in that position.
Next I got fed up and figured I'd over load that fuse in Hope's it would burn whatever wire causing the problem . But nope it popped 3 other fuses and shut my truck off. I'm at a loss on what to look for next as nothing should be hot on that fuse yet it's still arcing


Help... any ideas where I can look or what's causing this

 

I did all of that to no avail and I'm beyond confused... I disconnected everything attached to that circuit and it still blows the fuse immediately... there must be something I'm not seeing ... itll go to my mechanic soon as I can get home till then I'm lost

 

My truck is a 2000 international 9400i with series 60 Detroit 12.7l.... Vin # yc048685... if it helps at all...

 

Update.... it's still not fixed been trying everything I can think of and I cant seem to get headway... I've taken it to 2 mechanics while over the road to no avail.... I finally got home and took it to the shop I normally use and trust they had it for 3 days and it has boggled them as well... here's what they've done so far and I'm hoping it may spark something for someone to help...

My ac compressor and clutch are both brand new. But they didnt know what to do with high pressure switch on compressor so they bypassed it and put a new one with all new wires ... it stayed on while in shop enough to test the system for leaks and to fully vac and refill system and it ran for a day. I picked truck up and went 400 miles and parked woke up and it went haywire from hell... my truck shuttered and died completely... I checked everything with a test light looking not thinking ac would be the problem and sat on side of road for 3 hours till I pulled the same fuse and it allowed my truck to start...

So to test it that was problem I put circuit breaker fuse in and watched to see what is causing it to turn my truck off... with ac on I felt the circuit breaker get hot and then my ignition relay fuse (also a breaker I put in) popped and truck died.... not sure where or what to go looking for.... help