What are the symptoms of a faulty radiator fan resistor?
3 Answers
Radiator fan resistor failure manifests as: inability to adjust airflow volume; absence of 1-2-3-4 speed settings, with only a single airflow output. In some cases, the blower may not work at all. Below are relevant details: Resistor: A resistor is a current-limiting component that, when connected in a circuit, restricts the current flow through its branch to protect power devices. Function: The fan resistor primarily controls fan speed. There's a coolant temperature sensor near the engine's water outlet that adjusts the resistor's effective resistance value based on coolant temperature changes, thereby regulating fan speed to help control engine temperature.
Recently, I had an issue with the radiator fan in my car, and it turned out the resistor was faulty—really annoying. The symptoms were that the fan kept running at high speed non-stop, making a lot of noise, like driving a tractor. The air conditioning also didn’t cool properly. The temperature gauge kept spiking, especially in traffic, and I was worried about engine overheating damage. After taking it to the repair shop, they found the resistor was faulty, preventing the fan from switching to low speed. Now, after replacing it, it’s much quieter, and the AC works fine. I recommend regularly checking the fan noise and coolant temperature to avoid breakdowns—safety first, after all. By the way, this issue is more common during summer heat, so address it promptly and don’t wait until the warning light comes on like I did.
If the radiator fan resistor in your car is faulty, I can share some symptoms based on experience. The fan will basically only operate at high speed, with no response or function at low speed, leading to unstable engine temperature. The air conditioning cooling effect will noticeably decline because the condenser requires fan cooling while driving. Additionally, there may be increased noise, much louder than usual. Diagnosing it isn’t difficult—just check if the fan only responds at high speed when starting. I once inspected the circuit connections myself and found the issue was due to aging of the resistor module. After replacement, everything worked fine. I recommend fixing it as soon as possible, as prolonged neglect can lead to increased fuel consumption and component wear. Paying attention to changes in the fan noise can help detect these minor issues early.
