Gene,
Thank you for answering the following message I sent to you:
My Jenn-Air Double Oven is displaying the error code ‘‘FR’’ when trying to use the lower oven and won’t heat up.
The upper oven works half the time. Sometines the heating element comes on and turns red and works fine, and sometimes the heating element won’t come on and the digital display show 100 degrees. When the upper oven won’t come on, we hear a faint, high pitched squeal.
I pulled up a copy of the Service Manual on the internet, and it only says that the problem for the FR code is "Second Oven Error Sensed." Duh? In the next column it says to 1 "Check Sensor and Harness," and 2, Replace Second Oven Board.
Can anybody help answer the following questions please?
1.) What and how do I check the Oven Sensor? How do I know if it is bad or not? Where is it located? The manual does not discuss this, nor does it show its location.
2.) What and how do I check the Harness, and how do I know if it is bad or not. Further, where is it located as the Service Manual does not discuss this, nor does it show its location.
3.) Can the problem with the second oven board be the cause of the problem with the upper oven? Do I need to replace both boards? How can I tell if/which board(s) are bad?
Please help if you can. I need to order parts ASAP as my wife is refusing to cook any meals until I get the probalem resolved. Thx.
Unfortunately, there was one part of my inquiry you did not answer:
2.) What and how do I check the Harness, and how do I know if it is bad or not. Further, where is it located as the Service Manual does not discuss this, nor does it show its location.
The diagrams on the website for this appliance does NOT show a picture of the harness. What does it look like, where is it located, and how do I know if it is bad or not? Is there a way to check it? I know I get a new one as part of a kit when I order the lower oven relay board, but is it possible that I may only need a new harness and not a relay board at all. The manual suggests that this should be checked first before replacing the board. It would save me a lot of money (a couple of hundred $$) if all I need is a new harness. I would like to locate and test/check this please. Can you please help me out with this?
Additionally, for reasons I don’t want to get into, I could not pull the oven out of the cabinet to locate and check the the sensors like you suggested, but I did locate the plug/wires to the upper and lower sensors on the main relay board. I checked the sensors by unplugging them from the board and measuring the resistance with an ohm meter by touching the contacts at the plug. The resistance for both sesnsors measured right at 1100 ohms without the oven being turned on. This seems to be consistent with the manual that lists that the ohm reading at 100 degrees should be 1143. It isn’t a 100 degrees in my house (slightly cooler) but the ohm meter did only read at 1100. I could not measure these sensors at different temps like the manual suggests because neither of the ovens will heat up. Plus I don’t know how you would check the resistance at different temperatures with the oven out of the cabinet. That sounds pretty dangerous. Can I assume these sensors are fine based on the test I was able to perform?
I did order both boards last night from your company like you told me to in your response to my first inquiry, although I was hoping not to have to replace either board let alone the main relay as the main relay board is so expensive. Could you please answer the questions above related to the harness for me (what it looks like, its location and how to test it), as well as let me know if you think my sensors are fine based on test I performed above? Thanks. 
