Question: How do you diagnose a bad blower motor resistor?

Problems with a blower motor resistor are common in many cars. The most common symptom of a failed blower motor resistor is when the heater fan only runs at the highest speed setting (4 or 5) and doesn’t work at low speeds. In some cars, a failed blower motor resistor can cause a heater fan to stop working completely.

How do I know if my blower motor resistor is bad?

Bad Blower Motor Resistor Symptoms

  1. Only One Speed From Blower Motor. One of the most common symptoms of trouble with the blower motor resistor is when the fan gets stuck in one setting. …
  2. Various Airflow Settings Not Working. …
  3. No Air Coming From Vents.

How do you check continuity on a blower motor 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.

Can a blower motor resistor work intermittently?

Intermittent Operation

When the resister of the blower motor starts to fail, the motor operates only intermittently. … The higher current can make the jump across the resistor contacts that are going bad and get the blower motor to engage.

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Can a blower motor resistor be bypassed?

Blower resistors are made of several resistors with different resistances. … In the highest speed state, the blower resistor is bypassed completely and the fan is connected directly to the car’s battery, which allows maximum current through the motor.

What would causes a blower motor resistor to go bad?

In most cases, a blower motor resistor fails due to corrosion or overheating. Sometimes, the mechanical resistance to the motor rotation causes an excessive electric current that can overheat and prematurely damage the blower motor resistor.

Can a bad blower motor resistor cause no AC?

Another symptom of a faulty blower motor resistor is no air from the vehicle’s vents at all. … A blower motor without power will not be able to produce any air pressure, and as a result the heating and air conditioning system will be left with no air coming from the vents.

What are the symptoms of a bad blower motor?

What Are Signs Your Blower Motor Needs to Be Replaced?

  • Poor or Airflow from Air Vents. This will be the first and most obvious sign your blower motor has a problem. …
  • No Airflow At All From Vents. …
  • Skyrocketing Energy Bills. …
  • Strange Noises When You Turn on the Heat. …
  • Overheating Blower / Weird Smells.

Why do I have to hit my blower motor to work?

Blower motor only start working after i hit a bump.

In most cases that is a sign of worn down blower motor brushes not making a good contact. In some cases the blower motor/resistor pigtail could cause erratic operation of the blower motor too.

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