What was found
MVY-LGA, FLT 3690-ON APPROACH INTO LGA, THE RIGHT MAIN GEAR LIGHT ILLUMINATED RED. CREW PERFORMED A GO AROUND, CYCLED THE GEAR AND THE LIGHT INDICATED DOWN AND LOCKED. MAINTENANCE PERFORMED A PSEU TEST AND FOUND NO FAULTS. CLEANED DRAG STAY PROXIMITY SWITCH, CHECKED GAPS. CLEANED PROX SWITCH HARNESS CANNON PLUG IN FORWARD NACELLE. OPS CHECK GOOD. A/C RETURNED TO SERVICE. PROBLEM REOCCURED ON GROUND 31 JULY, MAINTENANCE REPLACED THE DOWN LOCK PROXIMITY SWITCH AT THAT TIME. TEST FLIGHT SATISFACTORY. AIRCRAFT RETURNED TO SERVICE.