Yes, the blower motor will often still work, but its behavior will depend entirely on exactly how the resistor has failed.
Diagnosing a faulty blower motor versus a bad resistor typically comes down to what fan speeds are working. If the fan only works on the highest setting, the resistor is usually the culprit. If the fan doesn't work on any speed, or if it makes strange noises, the motor itself is likely failing.
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.
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.
Signs you need a new blower motor include weak or completely stopped airflow from your vents, unusual noises (screeching, rattling, or grinding), and a burning smell from the dashboard or vents. You may also notice erratic fan speeds, the blower motor continually blowing fuses, or excessive vibrations.
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.
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.
A bad resistor typically causes a circuit to lose control over electrical current, resulting in failing components, completely dead systems, or visible physical damage like burns, cracks, or discoloration.
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.
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.
To test a blower motor resistor, set your multimeter to measure resistance (Ohms). Disconnect the resistor and measure the resistance between the common input pin and each speed pin. If you read "OL" (Open Line) or zero resistance, the resistor or its thermal fuse is blown and needs to be replaced.
A blower motor resistor (also called a blower resistor pack) is a set of high-power resistors—and usually a thermal fuse—mounted in the air stream of your HVAC duct.
When high speed is requested, the blower motor resistor is bypassed and the blower motor ground circuit is connected directly to ground. This allows the maximum current through the blower motor and maximum speed occurs.
A bad blower motor relay will typically cause your HVAC system to produce no airflow, blow warm air only, or leave the fan running constantly. It often fails due to overheated electrical contacts or melted wiring.
To test a blower motor with a multimeter, first disconnect the motor from its power source. Set your multimeter to the Ohms (Ωcap omegaΩ) or continuity setting. Check the internal windings by touching the probes to the motor's power terminals. A healthy motor will show a low resistance reading (usually between 555 and 505050 Ωcap omegaΩ).
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.
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.
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.
Blower motor resistors typically last between 5 to 10 years. However, there is no set mileage or exact expiration date. Their actual lifespan heavily depends on usage, the quality of the part, and whether your cabin air filter is regularly changed.
Resistors fail primarily due to excessive heat caused by electrical overload, which alters the internal resistive material or breaks the circuit entirely. Because they are designed to limit current and dissipate power, pushing them past their limits triggers the most common physical and electrical breakdowns.
While a fan stuck on high is the most common indicator, a complete loss of fan function on all settings can also point to a failed resistor. In some cases, the entire component can fail catastrophically, often due to a significant electrical surge or extreme heat.
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.
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 ...