I finally found it... the radiator tubes are blocked by sediments... I had it cleaned... okey na ulit. temp never goes more than half the guage even at high speeds and steep climbs.

NOW eto yung natutuhan ko... when trouble shooting, always suspect the least cost parts for repairs or replacement (ang laki ng gastos ko replacing the thermostat and thermoswitch)... exception of course kung obvious na yung sira... "putsa bakit wala ako preno??? ah kasi sira yung aircon... " labo noh???

Thanks tsikoteers!