my K5 blazer at some point in its existance before I owned it had A/C. The previous owner ripped all that out, but on the firewall on the passenger side is this big black box. I think it is the A/C evaporator (but I probably made that up) it has 2 metal pipes with fittings on the end of them sticking out of it, like something was at one time connected to it. What I would like to know is, since I don't have A/C now, and don't plan to install it, can that be removed? or is it tied into the heater core and unbolting it from the firewall (which it looks like you can) will dump coolant everywhere.