Change control_ops id_base value of plugins

Hi,

function simple_weather() {
		$widget_ops = array( 'classname' => 'weather-wdg', 'description' => 'Weather widget.' );
		$control_ops = array( 'width' => 200, 'height' => 300, 'id_base' => 'simple_weather' );
		$this->WP_Widget( 'simple_weather', 'Simple weather', $widget_ops, $control_ops );
	}

This is my widget strings. I changed id_base (weather), but the id were not renamed (id=”instance-simple_weather-04″).
When I change the simple_wetaher in “WP_Widget (‘simple_weather’…”, then the widget dissappear.

I want to rename the id=”instance-simple_weather-04″ to id=”instance-weather-04″.
Could anybody help me?

Thx,
Cavey85