The fan on my Maytag electric double wall oven is no longer running when it should. Appreciate any help that can be provided.

The oven has a cooling fan that normally runs when the upper oven is on, and continues running until the upper oven has cooled. However, it has completely stopped running with the upper oven.

The fan also normally runs anytime the lower oven is on, and it is still working fine with the lower oven.

Upper and lower ovens are both still operational, and run at the correct temperatures.

Looking for ideas on what to check, and how. From the symptoms and what I can find so far, I am thinking/wondering:

• The fan itself is OK (otherwise it would not run with lower oven?)
  
• The high limit switch is OK (otherwise fan would run continuously?)
  
• DLB relay???
  
• Board???