My TJ Sport has a new problem. The temp gauge dropped today below 100 while I was driving it. Is it a gauge or a sending unit? Never had that problem in forty years.
Your thermostat might be (probably is) stuck open. If that ends up being the problem install a new 195 degree non-store brand thermostat like a Stant or Mopar. Make sure it is NOT a fail-safe thermostat which is known to stick/fail open too easily and too often. Fail-safe means it's unlikely to fail in the closed position but it errs too easily in sticking open which still needs attention.