This video shows you tips for removing pet stains from carpet using ammonia and an Iron. I have been removing urine stains from carpet all over Tampa FL for several years and I have heard and seen all types of remedies for this particular carpet stain. Almost all pet urine stain remedies involve a hot iron as a catalyst to remove the stain from the carpet. I wouldn't recommend using ammonia to remove the urine stains since the urine salts in the stain will release ammonia as it absorbs any moisture applied to it.
In other words this cleaning trick to remove pet urine stains from carpet would work just as good if you used water without the ammonia mixed in. What works even better is pouring carbonated water, at room temperature, on the stain and then apply the towel and hot iron. It will pick up more urine with out the risk of adding more ammonia to the carpet. Pour carbonated water around the outside of the stain and circle inward. Then place folded towel over the area and apply the hot iron to the towel. Keep the towel moving and be careful not to melt the carpet in the process. If your concerned about scorching the carpet use a slightly damp towel under the iron. It will create more steam and help break up the urine stain.