My wife got what she thought was an f-1 code that said to call a service center but it went away ..,Now both ovens take forever to preheat ...like 20 minutes when they used to only take about 2 minutes..you could watch the temp indicator rise to 450 etc quickly.. all 4 oven elements glow but not for about 1 or 2 minutes, I checked the voltage at the terminals where the cord attaches and get 240