A bad blower motor relay prevents your HVAC system from functioning correctly by disrupting the power supply. Common symptoms include complete lack of airflow, a fan that stays stuck on, intermittent operation, unusual clicking sounds, or melted components around the fuse box.
If the blower motor relay becomes faulty or fails, it can result in issues such as the blower motor not starting, insufficient airflow, or irregular motor speed. In such cases, it may be necessary to replace the blower motor relay to restore proper function to the HVAC system.
To check a blower motor relay, locate the relay using your owner's manual, swap it with an identical working relay to test if the fan turns on, or test it manually. Manual testing involves listening for an audible "click" when power is applied and checking for continuity using a multimeter.
Common indicators that a relay is malfunctioning include unusual clicking noises, failure to activate, and intermittent operation. These symptoms can signal underlying electrical relay problems that require attention.
Nearly all of the relays on a car, including the blower motor relay are built to last for as long as the car does.
To tell if an electrical relay is bad, you can quickly swap it with a known good relay of the same part number, perform a click test with a battery, or use a multimeter to check coil resistance and switch continuity.
The average cost for a Blower Motor Relay Replacement is between $109 and $133. Labor costs are estimated between $50 and $73 while parts are priced between $59 and $60. This range does not include taxes and fees, and does not factor in your unique location.
Contact wear and corrosion are two of the most common. Relays can develop wear and arcing damage from the repeated operation, and it can also result in circuit failure. Contact wear and arcing damage can lead to high contact resistance and short-circuiting.
Set your multimeter to resistance mode and probe the two coil terminals (pins 85 and 86 on a standard five-pin relay). A healthy coil reads between 50 and 120 ohms on most relays. A reading of zero indicates a short, and an open-loop reading (OL) means the coil is broken and the relay needs replacement.
The method to reset a relay depends entirely on the type of relay you are using:
The blower relay has an important function and role in automobiles. It controls the starting and stopping of the blower and its speed to ensure proper air circulation and temperature inside the car. It works simply but efficiently to provide a comfortable ride for the driver and passengers.
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.
The blower motor fuse is typically a 20-amp to 40-amp fuse. Because fuse locations and sizes are highly specific to your vehicle, you'll need to check the exact year, make, and model's owner's manual or fuse box diagram. Common locations include the engine bay or under the dashboard.
Testing a blower motor relay involves a quick "swap test," an audible click test using a 12V battery, and a continuity check using a multimeter. This helps determine if your HVAC issues stem from a faulty relay, a blown fuse, or the blower motor itself.
If your car has these symptoms, you should check the fan relay:
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.
To test a relay to see if it’s bad, you can perform a simple bench test using a Multimeter set to Ohms/Continuity and a 12V or 9V battery. You will be testing two things: the internal electromagnetic coil and the switch contacts.
Relay lifespan depends fundamentally on the type of relay and how heavily it is loaded. Generally, mechanical relays last 10510 to the fifth power105 to 10710 to the seventh power107 switching cycles, while solid-state relays can exceed 10810 to the eighth power108 cycles or 10–20 years of continuous use.
Yes, a bad relay can still click.
Excessive Heat
Just as cold weather and moisture can damage relays, excessive heat can also shorten their lifespan. In vehicles, for example, high engine temperatures or a poorly ventilated fuse box can cause relays to overheat, triggering electrical malfunctions.
To test a standard automotive relay without a multimeter, you need a 12V battery (or a 9V battery), jumper wires, and a simple 12V test light or a 12V bulb. This setup lets you verify both the internal switch and the control coil.
When a blower motor relay repeatedly burns out, melts, or fails, it is almost always a symptom of an underlying issue drawing too much electrical current through the circuit.
An HVAC blower motor typically lasts between 10 and 20 years, with an average lifespan of roughly 12–15 years, depending heavily on regular maintenance, usage, and system conditions. Proper care, such as regular air filter replacements and professional tune-ups, can extend the life of the motor, while neglect can lead to failure in as few as 5–10 years.
Replace Worn Relays Promptly.
If you notice that a relay is beginning to show signs of wear, it's best to replace it before it fails completely. Waiting too long could lead to more significant damage or safety issues.