To bolster Grouper's point. When I was doing heating and air years ago a lady kept calling in "no heat calls". Everything's the heat was working fine. Finally I dug deeper and when I showed her that it was 72 degrees on my high dollar temp meter she claimed it was wrong. She pointed to a very cheap bimetallic thermometer that read 65. I waited until she got up to get coffee and went over and bent the needle. Didn't hear from her again until summer when she stated calling "No AC" calls. LOL