Q: No heat. Replaced coolant and replaced thermostat. Car is still overheating and has no heat. Only cold air comes out.

The heater not working in some cases may be related to the overheating problem you are also having. This may be due to a faulty heater blower motor or potentially a badheater core. As you may know, the heater core is a small radiator like unit that circulates the hot coolant from the engine through the heater core which then uses this warm coolant to heat the inside of the car with the help of the blower motor that blows the warm air through the vents inside the car. When the cooling system is not properly circulating coolant through the motor, this results in the warm coolant not being pumped through the heater core properly in order to warm the inside of the vehicle.

发动机过热可能是由于低冷却液水平等许多因素引起的恒温器, or a failing coolant fan switch. As you may know thecoolant fan switchhelps to maintain the proper coolant temperature by turning on and off at specific temperature thresholds. When this switch is not working properly, this can cause the fans to come on intermittently, all the time or sometimes not at all. When this happens you will notice a temperature spike and drop occasionally as the fan comes on and off. When your恒温器无法正常工作或堵塞，这将不允许冷却液通过发动机正确循环，这可能会导致发动机温度波动不稳定，或者在某些情况下只是保持热。如上所述，这也限制了温暖冷却剂流过加热器芯，这用它将温暖的空气吹入车辆的驾驶室。我建议让您的机械师的专家来您家诊断您的冷却系统。