My 7KW generator has a voltage drop to 15 volts when it gets overloaded. It normally resets itself, but this last time it didn>t. Does it need a new AVR?

Generators are very sensitive to RPM and voltage. Like an older car, very little if any voltage is produced at idle. Overloading your generator causes the RPM to drop and therefore the voltage. Actually, generators are designed to run best at full RPM aand not more than about 95% wattage loading. Don't know what you did but I'm not sure a voltage regulator(AVR?)will do the job, you may have burned out some of the windings or damaged the armature. If you continually over load the generator, you should probably consider a larger output model.