Could be flame sensor. I dirty flame sensor will cause this problem. Flame sensor is rod that is in burner, should be able to remove and clean with steel wool or dollar bill. Usually has white film on sensor preventing it from reading flame. Not sure how American Standard is but sensor normally has 1 screw holding into place in burner box. If you can get at it, it is easy to clean.
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Could be flame sensor. I dirty flame sensor will cause this problem. Flame sensor is rod that is in burner, should be able to remove and clean with steel wool or dollar bill. Usually has white film on sensor preventing it from reading flame. Not sure how American Standard is but sensor normally has 1 screw holding into place in burner box. If you can get at it, it is easy to clean.