I was going to bring up the duel thermostat set up on these cars too. There right there together and wont hurt replacing both while having to already dig one out in the first place. If Im not mistaken I actually think the cab heater circuit is the lower thermostat, top one is for the engine. If Im not mistaken.. This will be my second replacement in 3 years, probably going to reverse flow with a complete fluid change. They can be pretty testing. I've been poking around trying to avoid the inevitable hoping something else I've overlooked has failed.Welcome to the forumZ. Are you the original owner of the car? If not, you need to check and make sure there's thermostats in it. It has two. Are you running anti-freeze/distilled water mix 50/50? Check that. Make sure someone didn't bypass the heater core. If it all checks out okay, try a reverse flush of the heater core. It could be clogged. How many miles on that Caliber? I have an older brother that lived in Sparta for years. I used to visit and go up to Fall Creek Falls. Beautiful part of the state.