To check if your car's blower motor is bad, first turn the fan to maximum and listen for squealing, rattling, or clicking noises. If you feel weak or no airflow, test the motor directly with a 12-volt battery or check for power at the connector using a Multimeter.
To check if a car blower motor is bad, first test if power is reaching it by turning on the AC to max and tapping the motor housing; if it starts spinning, the motor is failing. Next, use a multimeter to check for voltage at the connector or test the motor directly with a 12V battery.
Inadequate Airflow Through the Vents
If you notice little or no airflow coming from your car vents, you likely have a failing heater blower motor. When the heater blower motor is damaged or worn out, it will not generate sufficient airflow for efficient heating or cooling.
Disconnect the blower motor from its power source. Attach the multimeter probes to the motor terminals. A reading close to zero indicates good continuity, meaning the motor windings are intact. A reading of infinity suggests a break in the winding.
A failing blower motor struggles to push air through your car's vents. The most common warning signs include weak or nonexistent airflow, squealing or grinding noises from behind the dashboard, a burning smell, or a fan that only works on certain speeds.
To quickly tell if your car's HVAC issue is the blower motor or the resistor, look at your fan speed settings. If the fan works only on the highest setting, the resistor is usually the culprit. If the fan fails completely on all speeds, or struggles and stutters, the blower motor is likely failing.
Resetting a blower motor typically involves cycling the power, checking for tripped thermal switches, or adjusting your thermostat. These methods apply to residential HVAC systems, though the exact steps vary depending on whether you are working on a furnace, an AC unit, or a car's blower motor.
A standard HVAC blower motor winding typically reads between 3 to 15 ohms. However, the exact value depends on your specific motor type, horsepower, and speed settings.
The blower motor resistor can be removed after the bolts have been removed. The wire should be linked to the blower motor's positive terminal, and the negative terminal should be attached to the blower motor's negative terminal. This will turn off the resistor and allow the blower motor to run at full speed.
Blower motors can overheat due to various issues such as dust buildup, a clogged air filter, or mechanical failure. If your HVAC system frequently shuts off or goes into “safe mode,” it might be because the blower motor is overheating.
Knowing the common causes of blower motor failure and how to fix them can save much time and money.
A car's blower motor typically lasts between 10 to 15 years (or about 100,000 to 150,000 miles). Designed to last the lifespan of the vehicle, its longevity is often shortened by dusty environments, electrical strain from bad resistors, or debris build-up in the fan.
Fixing a car's blower motor typically involves replacing either the blower motor resistor (if the fan only works on high) or the motor itself (if it makes noise, blows fuses, or doesn't spin at all). The assembly is usually located under the passenger-side dashboard.
Testing an electric fan motor involves two primary methods: checking for electrical continuity (with power disconnected) and testing for operation (by applying power). You can easily diagnose a faulty motor using a standard multimeter.
To test a blower motor resistor without a multimeter, rely on symptom observation and a visual inspection. If your fan works perfectly on the highest setting but fails on lower settings, or does not blow at all, the resistor is almost certainly the culprit.
Testing a blower motor with a multimeter involves four key steps: inspecting the motor manually, testing for power, testing the windings for continuity/resistance, and checking for grounded shorts. Always disconnect the power supply before performing resistance tests.
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.
Motor winding failures often present with telltale signs such as a distinct burning smell, excessive heat, frequent tripping of circuit breakers, and abnormal vibrations. The motor may also fail to start, run sluggishly, or suffer from a significant loss of power and efficiency.
Step-by-Step Guide
In newer applications, the blower motor resistor is actually a solid state module that sends a varied signal to the blower motor. The traditional blower motor resistor is connected to ground and wired in series with the blower motor assembly.
A car's blower motor typically fails due to age, electrical shorts, or restricted airflow that overworks and burns out the motor. Common culprits include worn-out bearings, debris buildup in the fan, faulty resistors, or wiring and relay issues.