Hey Andrew
You have 2 spare controllers??? Awesome
What PCB's are they? (MX-318/319?)
How did you get those!! Sneaky
Don't even think about changing it unless its broken... And if a controller does fail, never throw it out as you can near guarantee it's just a couple of FET's on the board.
From memory, 1 forum member modded the internal controller running it external before changing it to an infineon. All other attempts to modify the board have seemed to fail.
I'm leaving mine alone
The other night I fixed a MX-318 PCB (the one with the shunt mounted on side1 of PCB) before it had 5 beeps, I replaced the FETS and now it doesn't beep even without throttle connected - but plugging in a throttle it works!! (not sure for how long though..)
You can definitely 100% purchase an internal controller from GM - I paid $60USD via EMS over a year ago now and was sent a pack of circlips, MX-318 PCB (current at the time), new power wire (battery anderson connector), full pack of spare quick disconnectors + new controller to DIN socket harness
Not sure if it's the same price now, or what you get - but I'm sure it's available.
So how did you come across these controllers Drewmeister ??