Does the Redcat have an actual reciever or is it one of the ESC/reciever combos? If there's an actual reciever separate from the ESC I'd just buy a new ESC. You can find some decent cheaper ESC's on Amazon or eBay, I'd look for something that is about 100A and 2-3s Lipo compatible ?
I'd guess being a super cheap made Redcat RC and sounds like you picked it up used, it's time to upgrade to something worth while(no offense). The ESC is probably garbage and who knows what the motor has been through as it is probably on its last leg as well. I'd suggest buying a new brushless...