'91 CQ Radiator Fan Wiring Override

[Christopher Gharibo]

On hot days, the radiator fan/relay/wiring set up in my CQ can be
unpredictable. 

Until I can troubleshoot this, I'd like to have the option of manually
providing 12V to the radiator fan of my CQ via a switch.

What's the best way to accomplish this? I was considering running a wire from
the + battery terminal to the fan directly controlled by a defogger switch
from the inside.

Does anyone see problems with such wiring?