What was found
PHX - AIR TURN BACK - FLT 0032 - AFTER TAKEOFF, DURING CLIMB, NOSE GEAR WOULD NOT RETRACT. NOSE GEAR HAD BOTH RED AND GREEN LIGHTS ILLUMINATED. AIRCRAFT RETURNED TO PHX AND LANDED WITHOUT FURTHER INCIDENT. MAINTENANCE DISCOVERED THE S845 SWITCH, NOSE DOWN SWITCH, WITH HIGH RESISTANCE. REMOVED AND REPLACED THE NOSE DOWN PROXIMITY SWITCH IAW BOEING 737-300 AMM 32-61-00-1 AND 32-61-51-4. OPERATIONAL TESTS WERE GOOD.