1994 Honda Accord 1994 Accord Cooling Issues

I have a 1994 Accord that is over heating all of the time. I took it to Pepboy's wich I know is a no no but they said I needed to replace cooling fan, thermostat and flush the system and they wanted 500 bucks to do it. So I took it and the parts home to do myself. The 1st issue I came across is when I jumped both fans direct to power they both run fine.I am not really understanding why this car has a two fan system and what the reason for two seperate systems are needed for. But never the less, the fan that is called the condenser fan is not working properly when hooked up to the car, it comes on intermittently and only for a second or two at at a time. When I replaced the thermostat "and there was not one in the car at all" I noticed a lot of scale build up that was almost completley covering the sensor that is in the thermostat housing itself. I took me hours to clean all of the scale out of there before I installed the thermostat. Now onto the issue with the condenser fan, I am tempted to directly wire the fan to the ignition switch since I know the fan is okay it's just a sensor or switch somewhere in the system that is not working. I have three basic questions,

one- is the condenser fan there to help cool the water in the cooling system?

two-. If I direct wire the fan to something off the ignition switch what kinds of problems can I have.

three- with that amount of scale in the system I'm sure most of the sensors are caked with it, will a professional cooling system flush remove this scale and perhaps get the sensors working again?

Thank you so much,

Broke in Bakersfield