Just today i bought a new zoo med digital thermometer and it was working for a little while then started displaying ( L°F ) randomly. I can't find anywhere about what it means. At first i thought it meant low battery but i switched multiple batteries through it. It displays number again once i take it out of the tank. Any ideas would be helpful. I plan to get a new one just would hope to not have to if its fixable.
I've never had that problem but you should be able to exchange it where you got it from since it sounds defective. I believe they also come with a warranty and you could contact the company and see what they have to say about it.