If your cooktop or range has a radiant heating element or coil element that is not heating, you need to check the heating element for visual signs of damage.
You will need to locate the element under the cooktop surface that is not heating up and visually inspect it thoroughly to determine weather or not it has any damage. Look for cracks, burnt or chard spots on the element or a break in the radiant element coil.
If you have done a thorough visual inspection of the element and do not find any obvious damage, you will then need to do a continuity test with a multi-meter and determine weather or not the heating element has continuity or not.
If the element has continuity, then it is good and element should function properly, If the element tests show that it does not have continuity then it is bad and you will need to replace it with a new radiant surface element.
If your oven, range, stove or cooktop surface unit switch/infinite switch becomes defective, the element may stay on high heat when you turn it on, even if you have it set at the lowest setting. Of course, the heating element may not come on at all when the switch is turned on. The main symptoms when the switch becomes defective is too much heat or no heat.
If your stove, range or cooktops radiant element starts working erratically, the terminal wire ends on the range and element may be burnt or charred. This will cause the range element to lose electrical contact at times with the terminal block that it plugs into. It is quite often better to replace both of the range parts. If the terminal ends on the element unit are burnt then the contacts on the block are probably burnt also. If a new element is used with a burnt terminal block these repair parts may not last very long or give proper service.
