The low voltage alarm will sound when the DC source falls below 10 volts and the automatic shutdown will power off the inverter. This is done to save your battery(ies) so you can restart your vehicle.
My inverter's fans won't come onGood! On almost all of our inverters over 1000 watts, the fans are connected to a thermal switch which will only allow the fans to come on when they reach a certain temperature. This helps keep your batteries holding their charge longer, and also makes it QUIET! Hooray!