'86 Accord Fan will not operate while car is running

[Eggplant]

My '86 Accord LXi overheats because the fan will not turn on while
the car is running. If i shut the car off its hit or miss if the fan will
turn on. Obviously the sensor needs replaced (doing that in the
next few days). My brother said to jumper the sensor wire and the
fan will kick on and run all the time. The problem is that it does as long
as the car is off. I am wondering if the computer is dieing (every now
and then the PGM-FI light comes on) or if it might be some odd wire
problem?? Any ideas???