How do I know if it's my blower motor or resistor?

Author: scraper  |  Last update: Thursday, July 23, 2026

To quickly determine if your car's climate control issue is the blower motor or the resistor, test the fan speeds: if the fan only works on the highest setting or skips certain speeds, it is almost always the resistor. If it fails to work on any speed, the blower motor or its fuses are the likely culprits.

Can you run a blower motor without a resistor?

As we know, the resistor is responsible for controlling the blower motor's speed by regulating the voltage supplied to it. It will turn out that without the resistor, the blower motor may run at maximum speed or not function as expected.

Do I need a new blower motor or resistor?

Which one to replace? If high setting works and medium and low do not, replace the resistor. If blower motor is spinning but makes noise, replace the blower motor. If you hear noise and only high setting works, replace both.

What happens when a resistor goes bad?

When a resistor goes bad, its internal resistance changes. It will generally either fail open (stop the flow of electricity entirely) or drift in value (block too much or too little current). This can cause the circuit to malfunction, overheat, or fail completely.

What happens when a blower motor resistor goes bad?

When a blower motor resistor goes bad, the electrical pathways that regulate your fan's speed fail. This most commonly results in a fan that only works on the highest setting, skips certain speeds, or shuts off completely. In some cases, it can also cause a burning smell or melted wiring.

Heat Stopped Working In My Car! Blower Motor or Resistor?

How to test if a resistor is faulty?

To tell if a resistor is bad, perform a visual inspection for burns, cracks, or discoloration. Next, safely test it using a multimeter set to Ohms (Ωcap omegaΩ). Disconnect power, isolate at least one end of the resistor from the circuit, and verify that the measured reading matches the expected value.

How to tell if it's the blower motor or the resistor?

To determine whether your blower motor or its resistor is at fault, look at your fan's speed settings. If the fan only works on the highest setting, the resistor is likely bad. If the fan does not work on any speed, the blower motor itself or a fuse is usually the culprit.

How much does it cost to have a blower motor resistor replaced?

Replacing a blower motor resistor typically costs between $90 and $300 for parts and labor. The part alone runs about $20 to $100, while labor takes a mechanic 30 to 90 minutes, adding another $50 to $200 depending on your vehicle's make and model.

What is the most expensive part to replace in a furnace?

The heat exchanger is often considered the most costly part of a furnace to repair or replace. It is a critical component that transfers heat from the combustion process to the air that circulates throughout your home. Over time, heat exchangers can crack due to the constant heating and cooling cycles they undergo.

Can I use a paperclip as a resistor?

(1) Put the clip to the starting point of your strip(i.e. on the most lefthand side). (3) Next to this clip, put another clip ,leaving a space of around 1/2 to 1 cm. (4) Connect your multimeter probes to the clip and check the resistnance. (5) Adjust the position of the second clip to get the desired resistance.

Where is the blower motor reset button?

The blower motor reset button is usually a small, red or yellow button located directly on the motor housing, inside the blower compartment of your air handler or furnace.

How to bypass a resistor?

To bypass a resistor, you simply need to provide an alternate path with lower resistance for the electrical current to flow through. The current will naturally take the path of least resistance, effectively ignoring the resistor.

How to test a blower motor resistor?

Testing a blower motor resistor involves checking for physical damage and using a multimeter to verify electrical resistance. If your fan only operates on the highest setting or not at all, a faulty resistor is likely the culprit.

Can you test a resistor without removing it?

Resistors most often fail open, not closed as in a short circuit. So if you just wanna take a quick and dirty look, you can place a resistance meter across the component and you should get the resistor's rated value OR LESS.

What does a failed resistor look like?

A physically damaged resistor will often show clear signs of overheating or structural failure. Tell-tale signs include charring (black or dark brown burn marks), blistering on its paint or body, visible cracks, or a completely split and broken casing. You might also notice a strong, acrid burning plastic or electrical odor.

What happens when your blower motor resistor goes out?

If your blower motor resistor goes out, your car's heater and air conditioning fan will likely lose its ability to change speeds. The most common symptoms include:

How much would a mechanic charge to replace a blower motor?

The labor cost to replace an HVAC blower motor typically ranges from $150 to $400, depending on your location and the complexity of the job. This generally accounts for 2 to 3 hours of work at a standard hourly rate of $75 to $150.

Can a dirty cabin filter affect the blower motor?

Yes, a dirty cabin filter can absolutely affect your blower motor. When a filter becomes heavily clogged with dust and debris, it restricts airflow, forcing the fan motor to spin against higher resistance or operate in a starved air environment, which can eventually lead to premature wear and burnout.

Will a blower motor work without the resistor?

If one of the resistors is burned out, the only speeds that will work are the speeds above the burned out resistor. A blower stuck on a high-speed setting will keep blasting you with hot or cold air when you don't need it, though one that's stuck on the low setting can be just as frustrating.

How to test if a resistor is blown?

In this case, we see the resistor value by a multimeter and try to compare it to its actual value. If the measured multimeter value matches the given actual value of the resistor we say the resistor is good, else you have a bad resistor.

How to identify a bad blower motor?

Check out these four signs of a bad heater blower motor.

  1. Inadequate Airflow Through the Vents. ...
  2. Unusual Noises or Vibrations When the Fan is Running. ...
  3. Defroster Does Not Clear Glass Well. ...
  4. Smoke or Burning Smell Coming Out of the Vents.

What happens if a resistor goes bad?

When a resistor goes bad, its internal resistance changes. It will generally either fail open (stop the flow of electricity entirely) or drift in value (block too much or too little current). This can cause the circuit to malfunction, overheat, or fail completely.

How to check resistor without multimeter?

If so, by hooking it to, say, a 9 V battery in series with one or the other resistor will tell you right away, as the lamp will light much brighter when the series resistor is the 110 Ω one, as compared to the 1000 Ω one (it might not be visible at all with the latter at least in normal lighting, but should be with the ...

How do I test a resistor using a multimeter?

Testing a resistor with a multimeter is simple: power off the circuit, isolate the resistor, set your multimeter to measure Ohms (Ωcap omegaΩ), and touch the probes to the resistor's leads.

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