oven preheats, but then loses temp (GE electric oven model #: jk5000fs5ss)

[rhalt]

Having a problem with my GE electric oven (model #: jk5000fs5ss). It is a 27" wall mount with conventional and convection bake options. The oven pre-heats to the correct temperature, but then steadily loses heat. If we stop the bake and restart immediately, we'll note that the temp has dropped drastically. For example, if we set the temp to 350, it pre-heats to 350 fine. If we check the oven 15 minutes after finished pre-heating the temp is down to around 300. At this point we will restart the bake at 350 and the oven will reheat back up to 350 and the same cycle repeats itself. You can imagine how frustrating this is when you are trying to cook something for 30 minutes at 350! Further, since we have to restart the pre-heat cycle in the middle of a bake, the top broil element turns on during pre-heating and is burning the top of our bakes.

I have tried a number of the things with no success and would be keen to hear if anyone has suggestions. I've replaced the temp sensor and control board and have confirmed all the elements work independently. I thought this was going to be a control board fix, but no luck.

Any suggestions on this one?

[BryanS]

Ovens don't hold a set temperature. The temperature comes to average over a period of time. For instance GE ovens I've noticed that they don't overshoot during preheat like others brands, but they will cycle above set temp after this first up and down cycle. The ovens use the high and low temps average. Say you get 4 readings after it reaches the highest point and lowest point of the element cycling on and off, then you add those 6 temp numbers and divide them by 6 for the average temp. A lot of the cheap metal store thermometers aren't accurate.