Help! We have an American Standard Freedom 80 that's about 7 years old. When I turn it on the motor starts up and I can hear clicking noises and then it shuts down but the fan continues running.

I took the cover off and the light is flashing 4 times indicating "open high temperature limit switch". can you tell me what that means and if we are able to fix it ourselves?

Thank you so much in advance for your help.

Karen