When a dell tech changed one of the 2 internal fans ( in front of the bays ) in my 7820 ( it's the same chassis ) , he run the system with the lid open to make sure which of the 2 fans needed to be substituted. A simple screwdriver to keep the intrusion detection button pressed, was enough. There's no reason this (keeping the button pressed somehow) wouldn't work in your case ( by logic ). On a side note, there's no reason to cut wires or whatever. just look at the part that engages the intrusion detection, on the side cover... make something of the same dimension, fit inside the switch and keep in place using electric tape. Simple, easy, not intrusive, nothing gets damaged , and the tape peels off without leaving marks on the plastic ....
Hi, I have a precision Tower 5820 and i cannot disable Chassi Intrusion detect! I would like to power on my computer without the side cover because the  air cooling inside of chassi is very bad! I tried all ways, i tried all Bios Security Chassi Detection options and no one works... I tried too disable the security circuit cable from the board, and if this cable is disconnect the computer doesn't power on! I need help!!!
Precision 5820 - Cannot disable chassi intrusion!