What are the symptoms of a faulty car blower resistor?
3 Answers
The symptoms of a faulty car blower resistor are: the air conditioning does not blow air at a certain speed setting, for example, speeds 1, 2, and 4 may work, but speed 3 does not. The solution is to replace the blower resistor. The function of the car blower is: to blow the cold air from the air conditioning evaporator or the hot air from the heater core into the car. When the blower is turned on, if the temperature is set to the lowest, the external circulation will bring in the natural temperature of the outside air, but it will be slightly higher because the air intake for the external circulation is generally located between the lower edge of the front windshield and the engine compartment, which will carry in some of the engine compartment's heat. If it is in internal circulation, the air blown out will be at the temperature inside the car.
I had the exact same issue last time. In the middle of summer, the AC would only blow at the highest setting - the lower fan speeds felt like they weren't even on. When cranked to setting 4, it roared like a broken blower, making conversation impossible in the car. The weirdest part was how the fan speed would suddenly jump on its own - I'd set it to 2 but it would rocket up to 4. The mechanic took one look and said the resistor was burnt out. Replaced that small part and it was fixed immediately. A word of warning: never keep driving with this broken, especially in rainy weather when you can't adjust the fan speed to defog the windshield - that's downright dangerous.
I know a bit about this. There are several symptoms when the blower motor resistor fails, all related to fan speed control. Normally, each fan speed setting should gradually increase the airflow, right? But if the resistor is faulty, you might find that the lowest three speed settings don't produce any airflow, leaving only the maximum speed setting functional, which would definitely be extremely noisy. In some cars, the issue might manifest as the fan speed switch being unresponsive, or when you select speed 1, you get the airflow of speed 4 instead. Older vehicles with aging wiring are particularly prone to this problem. Never attempt to disassemble it yourself recklessly—you need to check if the resistor module is blown or burnt out. After all, it's connected to the blower motor, and improper handling could potentially affect the entire vehicle's electrical system.
