Repairing a Thermometer

We had given our son a thermometer when he went to college and later to a job in another city. When he came home last week on vacation, he brought it back because it was not working. "I have to keep it in the axilla for long periods, and still the temperature does not rise much." He did not tell us why it was so. "Let us throw it away and give him another one" my wife said. We gave him another one, instead of asking him to get one after going back after the vacation, because we were more concerned about his health, and knew he would procrastinate. But I wanted who see why the thermometer would not work. I had fixed electrical appliances, mechanical appliances and computers in the past, but not a thermometer. I examined it and found that a small bit of mercury was lying in the capillary tube at the level of 1080 F. I wondered how it got detached and reached such a high level. Perhaps he had dipped it in warm water. I kept the thermometer in the refrigerator but it remained as it was. Then I had another idea. I dipped it in warm water and the mercury expounded and met the tiny part at 1080F. I shook it back to the bulb anal all of it went back. I tested it and it worked. It did show the temperature one degree less than on another thermometer. But then I could always add one to whatever reading I got.