So to start off be patient with me please, I’m new to diesels, and working on my own stuff in general. I’m young and don’t know a whole lot about anything. But a few months back I had to replace the vp44 on my 2001 5.9 Cummins. Me and my dad had to work on it at separate times since he was working nights and I was working days. Well we eventually got it off and the new one on. And when we got what we thought was everything plugged back in and ready to go we went to try it and the two wires that connect to the two studs on the same side of the intake horn for the grid heater we’re left undone and we’re laying against something. So when we started it I went to the front and seen the wires spark, I ran around and shut the truck off. Now when we try to connect the two wires to the studs, wires get hot and start smoking. Even when both batteries are unplugged when we put the wires on and try to reconnect the batteries the wires to the batteries start getting hot. Does anyone have an idea what could be going on, like I said I’ve not worked on diesels a whole lot and am needing help. 

Most likely the grid heater relay are stuck on. Double check the relays on the fender to be sure they have opened. If stuck your going to have to replace them. Very possible that when the wires where left touching the block that the high current welded the contacts solid so it can't release. 

 

First disconnect the batteries. Now remove the large leads from the relays on the fender. Now with a DVM on "Ohms" check the ohm across both post of the relay. It should be infinite for a normal relay. If the relay is welded then the ohms will read ZERO or dead short. This means if you hook up the batteries the electricity is going to grid heaters uncontrolled. The grid heater itself is a very low ohm dead short like 0.2 ohms. Should never be a perfect ZERO either.  

 

Relays should not pass any power to the grid heater without the key on. This is the job of the relays to control the power to each grid heater elements. There is two 95 amp grid heater elements for a total of 190 amp draw with both elements going. 

 

Second tip... If you in warm weather you do not require a grid heater till about 32*F outside. I typically just unhook the two wires from the driver side battery and leave the grid heater unhooked all summer. April is unhook, and October is hooked back up for Idaho. These trucks do not require a grid heater for warm climates above 32*F. Most of the people in southern states just delete the entire thing. Not knowing where your at since your profile isn't filed out nor your signature.