using only 2 channels of 4 channel amp

Hello all, my roommate wants to install my old Profile California series amp on his 03 ford ranger. The amp is a 4 channel amp, however he only wants it to push one sub (single voice coil). Will anything bad happen if he bridges the rear channels to one to push his sub, and just not hook anything up to the front channels? Thanks in advance for any and all help guys! PS- I know Profile isn't all that great but, in my defense, it was my first amp ever (high school 2001, haha)

An amplifier will not produce power if there is no resistive load on it.  Channels 1 and 2 (the amplifier in question...the front channels) would just remain unused if you don't connect speakers to them.  It is perfectly fine to do so.Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.