How do you wire the fan to stay on if you think it is not coming on?

You don't want to wire the fan "always on". It'll kill your battery when not running. There is a heat sensor near the thermostat housing in my GM 3.8L that controls the fan. Because GM wants the engine running hot for fuel economy, the fan is triggered at 224 degrees even though the "stat" is set to open at 190 degrees. If you can't hear or see your fan operating after the engine is really hot, check the fan motor and the sensor to see which isn't working. You didn't say if you are boiling over so unless you're in Alaska, I suspect the fan is working OK.