My kenmore cooktop wont turn off even if i already turned the knob to off.it wont turn off the burner so i have to turn off the main gas line to shut it down.

SOURCE: Burner knob wont turn

appliance repair and yes you can fix it you likely need an infinite switch

SOURCE: (2) front Burner igniters on my new Matag 30" Cooktop continue to click

Sounds like water got into one of the switches. This usually happens when you wash the knobs. Water stays in the holes and runs down the shaft when replaced. Maytag has issued a recall on some stoves because this can be a fire hazard. UNPLUG THE COOKTOP UNTIL THIS IS FIXED!!!!!!!!! This has happened to me with a whirlpool unit and it tripped a breaker and shot sparks across the kitchen. First go to Maytags web site and see if yours has a recall. If so Maytag will fix it free. While you are waiting leave stove unplugged and light with a match. If you need to fix this yourself disconnect the wires from the two switches this should stop the sparking. Connect one switch at a time and see which switch is bad. Most of the time the electric part of the gas valve can be replaced seperately. and you can do this yourself. If you must actually disconnect a gas pipe unless you really know what you are doing call for service.

SOURCE: old Thermador cooktop continues to spark even after turned off

sounds like you have a bad switch. maybe on the large burner.. some of those switches can be replaced without the whole harness.

SOURCE: miele gas cooktop flame shuts off after lighting.

I had similar problem.Solved by Miele tech by placing rice grain sized wad of paper towel inside knob so it sits slightly higher on the valve shaft.

SOURCE: GASS COOKTOP-electric ignition sparks continuously w/gas is of

Hi,
Here is a tip that I wrote that will help you with that...

http://www.fixya.com/support/r4033033-gas_range_repair_burners_keep_clicking

heatman101