What was found
THE LANDING GEAR RETRACTED, BUT WOULD NOT EXTEND WITH HYDRAULIC PRESSURE, ALTERNATE GEAR EXTENSION WAS USED AND THE GEAR EXTENDED. TROUBLESHOOTING REVEALED THE GEAR UP SOLENOID WAS RECEIVING 28 VOLTS WITH THE GEAR HANDLE IN THE DOWN POSITION. FOUND THE LEFT SQUAT SWITCH FAILED INTERNALLY ALLOWING 28 VOLTS FROM THE ANTI-SKID YSTEM AND THE LEFT BLEED AIR SYSTEM TO POWER THE GEAR UP SOLENOID. REPLACED THE SQUAT SWITCH AND FUNCTIONALLY TESTED THE LANDING GEAR SYSTEM.