Well, it happens when you start your engines consequently, all you have to do is to go to the ELEC ENG CONTROL which is located beside the IRS control open the guard for switch 3 and press it, a warning light will illuminate "ALTN" on the same switch and the off light should go off from the GEN CONT 3 switch, after that switch ELEC ENG CONTROL 3 back to normal and close the guard, and you are ready to go.