How to tell if a blower relay is bad?

Author: Zora Corwin  |  Last update: Saturday, January 3, 2026

Symptoms of a Bad Blower Motor Relay On platforms where the blower is directly controlled by the switch rather than a module, the relay will cause the blower not to work at all, which means there will be no airflow across the evaporator, and the effect will be the same as the A/C not working at all.

How do I know if my blower relay is bad?

No Airflow: One of the most noticeable signs of a bad blower motor relay is the lack of airflow from the HVAC system. If the relay fails to activate the blower motor, it will lead to no air coming out of the vents, resulting in poor heating, cooling, or ventilation performance.

How to check if a fan relay is bad?

A faulty relay can be caused by a bad relay control module, ants in the relay, or an electrical short. To check for a faulty relay, you can swap relays, measure the relay coil's resistance, or listen for noises from the relay. A broken relay will rattle.

How do I know if my blower control switch is bad?

A bad control switch won't be able to accurately change your A/C system's settings. The button will most likely refuse to respond even if you try to increase the fan speed.

How do I know if my fan control module is bad?

The fan stops blowing air: Anyone who has driven a car will realize that there is a problem when the fan isn't running when the air conditioning is on. If the cooling fans are not running at all, then this may be a sign that the fan control module is damaged.

How to test and replace a Blower Motor and Resistor | No heat or A/C help.

What happens when a relay goes bad?

Some of the symptoms of a bad ignition relay include an unresponsive ignition switch, stalling, and a drained battery. Your vehicle can also start intermittently. A brand-new ignition relay typically costs around $10 to $100.

Will a bad relay still click?

Yes. the contacts inside a relay wear out over time to the point they don't touch or oxidation builds up to the point where the contact resistance goes so high. also a relay will click whether a load is a attached to it or not as long as the coil is fine and the mechanism inside is still functioning.

How do I know if I need a relay?

If you need to activate a heavy load, high current device using a small, light load switch – you will need a Power Relay!

How does a blower relay work?

The blower motor relay has a small electromagnetic coil between the primary (trigger) terminals on the relay. The core of this coil is soft iron and becomes a powerful magnet that pulls the secondary (load carrying) contacts together. Thus, the relay is basically an electromagnetic switch.

Why isn't my fan kicking on in my car?

The most common reasons for a radiator fan not working can be a blown-out fuse, a bad relay, or a broken wire. The faulty coolant temp sensor might also be a reason behind it.

How much does it cost to replace a fan relay?

The average cost for a Radiator Fan Relay Replacement is between $85 and $92. Labor costs are estimated between $27 and $35 while parts are typically priced around $57. This range does not include taxes and fees, and does not factor in your unique location. Related repairs may also be needed.

How to tell if your fan relay is bad?

the fan doesn't turn off.
  1. Engine overheats. There are many reasons for engine overheating. ...
  2. The fans don't start. This problem follows from the first. ...
  3. The air conditioner does not work well or does not work at all. Most likely, the problem lies in the damage or obstruction of the highway. ...
  4. The fan doesn't turn off.

How do you diagnose a blower motor problem?

Look for these key indicators that you have a bad blower motor.
  1. Strange Rattling, Clanking, or Screeching. ...
  2. Weak or No Airflow From The Vents. ...
  3. A Sudden Spike in Your Energy Bills. ...
  4. An Overheating HVAC System. ...
  5. Replace or Maintain a Part in the Blower Motor. ...
  6. Replacing the Blower Motor. ...
  7. Keep Up With HVAC Maintenance.

Is a blower motor relay the same as a blower motor resistor?

These are different components. The blower motor high relay will affect high speed blower operation. The blower motor resistor will vary the lower speeds.

How do you test a relay to see if it is bad?

You can also test your relay's functionality by switching your multimeter to test for resistance. This process involves switching your multimeter to read ohms and connecting the two leads to pins 85 and 86. A functioning relay coil should have a reading of between 50 and 120 ohms, but usually it's very near 75 ohms.

What is the most common problem found with a relay failure?

The two most common failure mechanisms of relays are contamination and mechanical wear of the internal switching elements discussed as follows: a. Contamination is a major cause of early life failures.

Will a bad solenoid still click?

One possibility is the solenoid. A single “click” sound comes from the engine compartment or from under the car. This could mean that the solenoid is trying to engage but that the internal components are stuck and unable to work properly. Repeated “clicking” sounds usually indicate a dead battery.

What is the life expectancy of a relay?

General purpose and power relays typically have an electrical life expectancy of at least 100,000 operations. This means they can switch on and off 100,000 times before potentially failing. The actual lifespan can vary based on factors such as load conditions, operating environment, and maintenance.

Can a bad relay drain a battery?

Parasitic draws, such as interior lights, door lights, or faulty relays, can drain the battery even when the car is off.

How do I know if my blower control module is bad?

  1. Symptoms of a Bad Blower Motor Control Module.
  2. A blower motor control module is crucial for your vehicle's HVAC system. ...
  3. * No Airflow or Weak Airflow.
  4. One of the most telling signs is if the blower motor isn't blowing air at all or the airflow is weaker than usual. ...
  5. * Intermittent Operation.

What are the symptoms of a faulty fan switch?

Here are the key symptoms to look out for:
  • Engine Overheating 🌡️: One of the most obvious signs is your engine running hot. ...
  • Cooling Fans Not Working ❌🌀: If you notice that your cooling fans aren't turning on at all, this is a strong indicator that the relay may be bad.

Previous article
How often should you grout your shower?
Next article
How do you reverse water stains on wood?