What does the indicator light on the temp control that looks like an open book followed by an exclaimation point mean? Please help.

 

It means service is needed for your heating/ac system. For me it meant I was low on Freon. For other I have heard that it is often on due to the blower/blend motor.

 

Could mean many things, test the functionality of your entire a/c system hot and cold. switch vent positions etc. The light just indicates something is wrong, and then leaves the guessing to you lol. If everything is working fine, it could just be a sensor malfunction.

 

Mine was doing the same thing, and took it in and it was the plenum air filter needed to be changed. No easy task. But after it was replaced the indicator went off. So yes it could be a number of things.