Q.pear not producing
My sand pear tree was loaded with pears every year until the last three years. Now it does not have any. My pear tree is old. Is that why it would stop producing?

Though a Pear Tree can live up to 50 years it would likely not be still producing fruit and would be susceptible to disease.
In the home garden a Pear Tree usually will stop producing after about 10 years. There is usually a slow down of fruit over a couple of years and this can signal the time to remove and replace the tree.
Here are some links for you.
https://www.gardeningknowhow.com/edible/fruits/pear/growing-pear-trees.htm
https://www.gardeningknowhow.com/edible/fruits/pear/growing-pear-trees.htm