I should also say if that does not take care of it it will be something to do with vacuum switch or vacuum hose as said by previous post, because heater systems are simple in design
Flush system if you have not done it before, change cap, and make sure system is full of proper coolant
I had same problem with 2003 chevy impala and the cap was bad!
I was born and raised in Fl I love it , we have a variety of things going on all the time! I just depends where you are moving to. Plenty of sun and humidity , sand and swamps, snakes and bugs, and alligators!
I rebuilt a AX15 about 1.5 years ago I replaced a lot of stuff in it, I got the info off the Internet and printed it out.as long as you have a knife edge puller and a press it is a breeze! The hardest time I had is with the shifting arms but common sense will go a long way with that mine still...