Examined unit. Noticed vat was closed on this unit, other 3 had open. Opened and closed door several times, fan always shut off. Pulled top panel to test switch, works and looks perfect. Put pan of water and closed vent on another oven. Steam came out. Did same with this oven, steam also came out with vent closed. Top panel on bottom ovens very hard to remove and put back on. Tightened screws on switch.