oven shuts down

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[SIZE=3]: We have a Jennair downdraft stove model jds9860aap. Thereis a problem with the oven. It shuts down on its own after it has been on forabout 30 mins. I have been able to take off the front panel and noticed a fan(probably for cooling) in the back top corner. In researching I discovered thata Hi-limit temperature switch controls this fan. I was able to pull the stoveout of its stall and set oven to 450 degrees. At approx 220 degrees I heardcooling fan run for about 10 seconds then quit. This happened at about every 30- 40 degree increase in temperature. Once oven reached the 450 degree mark,tone sounded that temperature was met. I only notice fan once for about another10 seconds then quit again. Oven will eventually shut itself down and restartonce it has cooled on its own. I am not sure if my problem lies with thisswitch or if the fan is faulty. Should this fan be running at longer intervals?[/SIZE]
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