Why does my blower fan only work on high?

Most car manufacturers use a series of resistors to make the heater blower motor run at different speeds. And when one or more of these resistors burn out, you’re usually left with only one heater blower motor speed—high. The resistor module is easy and inexpensive to replace.

What are the signs of a bad blower motor relay?

If you have a faulty blower motor, you may experience low airflow from the vents, even when the fan is on high. There will be no air coming from the vents if your fan isn’t working due to a bad blower motor resistor.

Can a blower motor resistor be intermittent?

Reduced airflow is when the blower motor is trying to move air through the vents but the resistor isn’t sending enough power to move the air with much pressure. Depending on how much resistor is still functioning, the reduced airflow could be an intermittent problem.

Why does my air only work on high?

When a blower resistor fails, the highest fan speed usually is the only one that still works because it essentially bypasses the resistor and receives the maximum amount of voltage. When the resistor is working, it reduces the amount of voltage going to the lower fan speeds, so the fan runs slower.

How do you test a fan resistor?

Place one lead of the Ohmmeter on terminal 1 of the resistor. Place the other lead on terminal 2 and check against specifications. If this circuit is open, showing infinity on the Ohmmeter, the blower resistor must be replaced. Move the lead from terminal 2 to terminal 3 and check this reading against specifications.

Why does my car blower only work sometimes?

When a resistor fails, the fan will often run only at higher speeds or the highest speed, no matter what fan speed is selected. If little air is coming through the vents (hot or cold), then it could be because the blower motor for the fan or a switch or resistor that controls fan speed isn’t working.

Why does my AC work on low but not high?

What does a resistor do on a cooling fan?

The cooling fan resistor is an electrical resistor that limits power to the fan in steps, so that the fan can operate at different speeds according to the cooling system’s demands.