Hi, guys. I got a call this AM, A Blodgett oven Not working properly. The temperature lost control. The food in the oven not well done as used to be.I knew the temp prob or the potentialmeter was malfunctional, but I am not sure which one is the real bad guy and I don't want to make double trips. So, I ordered both parts. After I changed them,the oven worked fine. My question is how do you guy find out which one is the real malfunctional parts in this case. the model# of the oven is DFG-100-3.