My Jenn-Air JDR8895aaw range has two electric ovens. The smaller oven works fine. The lower main oven bakes and broils fine, but While Preheating, only the lower element comes on. AS a result it can take 15 minutes, and usually much longer. The upper element, on all my previous ovens, came on also during preheat. They both come on when the upper smaller oven preheats.

Does anyone know the cause?
Thank you!