heated seats problem
 

04 Z71 crew cab, power everything and electric heated seats. My problem started yesterday. There are 3 settings for the seat heaters,low ,medium and high. when i turn on either front seat heaters to either meduim or high they stay on for a few minutes then turn themselves off. When it is on low they will stay on as long as the truck is running or I turn them off. (which is the way it has always been for any setting before).Don't know where to start looking. Any help would be appreciated. thanks,