Normal Interaction. Under most circumstances, a bad thermostat will not have any effect whatsoever on the air conditioning system. A stuck-open thermostat will constantly send coolant through the radiator to cool, meaning that the coolant — and thus the heater — may never reach its full operating temperature.Click to see full answer. Also asked, what are the symptoms of a bad AC thermostat? Common Symptoms of a Bad Home Thermostat The Heater or Air Conditioner Refuses to Start. Air Conditioner Runs Constantly and Won’t Turn Off. Changing the Batteries Did Not Help. There Are Differing Temperatures Throughout the Home. The Thermostat Has No Power or Is Unresponsive. Furthermore, why is my AC and heater not working in my car? A low antifreeze/water level in the radiator due to a leak in the cooling system. A bad thermostat that isn’t allowing the engine to properly warm up. A blower fan that isn’t working properly. Also Know, how do I know if my thermostat is broken? The most common signs of a broken thermostat are: Thermostat display is off or is non-responsive. Turning on the heat or AC does nothing. The heat or AC will come on, but either stays on nonstop or cuts out before the temperature setting is reached. Can a bad thermostat cause AC not to cool? AC Problems a Thermostat Might Cause If the thermostat’s temperature sensor is malfunctioning, it may start to shut down the ACs cooling cycle prematurely. No cooling at all: The air conditioner fan is running, but the air coming from the vents isn’t cool.