If the pressure is too low (AC low-pressure switch), the compressor risks damage due to running with low oil. If it is too high (AC high pressure switch), the compressor is at risk of overheating and becoming damaged. Depending on which side of the system the sensor is mounted in, wh...
So turn on your A/C compressor and see if one of those fans comes on. Then the other one will be for the radiator. As far as no heater/hot air. I am assuming that is because there is no hot coolant circulating in the engine. When the engine is warm, feel both upper and lower ...
If the pressure is too low, then the risk is that the compressor can burn out. It will then be unable to compress the refrigerant from liquid to fluid, which will see your car AC unit grind to a halt. If the pressure is too high, it could burst the compressor causing a leak of ...