Okay, friend, your problem is either the pressure valve or the resistor.
1. The pressure valve isn't sending the signal, or the relay for the second speed is bad; you need to locate it.
2. If the resistor is bad, disconnect the two wires connected to it. This resistor is located below the electric fan. After disconnecting the two wires, check if it turns on when you connect the two ends. If it works, then the resistor is bad.
3. If not, install a relay that, when the compressor turns on, sends current to the electric fan so the pressures are maintained and your car cools.