Connect a test light or multimeter to the ground (black lead). Turn the ignition key to the on position (engine off), and remove the relay. Using the probe, test all terminal sockets in the relay connector. Two of the four should have power.Take out the car’s blower motor relay. Read the grounded relay with your multimeter (Ohm scale). Then check the current pin while not grounding it to the multimeter’s DC scale.
What causes blower motor relay failure?
In most cases, a blower motor resistor fails due to corrosion or overheating. Sometimes, the mechanical resistance to the motor rotation causes an excessive electric current that can overheat and prematurely damage the blower motor resistor.
What happens when a blower motor relay goes bad?
If the blower motor relay develops any sort of problem that hinders its ability to properly limit and distribute power, it may cause the blower motor fuse to blow. Any sort of electrical spikes or excessive current from a bad relay will blow the fuse and cut power in order to protect the system.
Is there a way to test a blower motor resistor?
Place one lead of the Ohmmeter on terminal 1 of the resistor. Place the other lead on terminal 2 and check against specifications. If this circuit is open, showing infinity on the Ohmmeter, the blower resistor must be replaced. Move the lead from terminal 2 to terminal 3 and check this reading against specifications.
How do I know if my blower motor relay is bad?
If you have a faulty blower motor, you may experience low airflow from the vents, even when the fan is on high. There will be no air coming from the vents if your fan isn't working due to a bad blower motor resistor. Blown relay circuit fuses or melted relays are more serious signs of a bad blower motor relay.
How do you tell if a blower motor resistor is bad?
Signs of a Bad Blower Motor Resistor Loss of HVAC fan control (total or certain speeds) The fan only works on its highest speed setting. No air coming from vents. Intermittent or inconsistent fan speed.
How can you tell if you have a bad relay?
You want to feel and listen for any clicks. If you feel and hear clicks, the relay works on one side – the side with the energizing circuit and coil. However, if there was no sound from the horn, the relay has a problem along the contact circuit.
How do you check a relay?
The only tool required to check a relay is a multimeter. With the relay removed from the fuse box, the multimeter set to measure DC voltage and the switch in the cab activated, first check to see if there are 12 volts at the 85 position in the fuse box where the relay plugs in (or wherever the relay is located).
How many ohms should a blower motor have?
How Many Ohms Should A Blower Motor Have? A good blower motor is expected to read over 0.5 Ohms.
Will a blower motor work without the resistor?
Without any power, the motor won't run. As a result, the blower fan stays still and silent, and no air blows out of the vents. There are instances where a bad resistor will prevent the current from reaching the blower motor altogether.
Is there a fuse for the blower motor resistor?
A fuse is often located on the resistor board. The fuse only protects the low and medium blower speeds. High speed will still work if the resistor fuse is blown.
Is it the blower motor or resistor?
The blower motor resistor is an electrical component that is a part of the vehicle's heating and air conditioning system. It is responsible for controlling the blower motor's fan speed.
How does a blower motor relay work?
In a blower motor, the relay supplies the power that allows the fans to circulate warmed air. Essentially an on/off switch, the blower motor relay's reactions start and end the heating process in HVAC systems by controlling the flow of current between the power source and the motor.
Is there a fuse that controls the blower motor?
Many vehicles have two fuses for the blower motor, one in the interior fuse block and the other under the hood. The blower motor is usually under the dashboard on the passenger side.
What happens when blower motor resistor goes out?
If the resistor shorts or fails, it may cause the blower motor to remain stuck on one fan speed. The heating and air conditioning systems may still function at one speed, however the resistor will have to be replaced in order for full functionality to be restored.
Where is the blower motor fuse and relay?
Under the instrument panel, look under the glove box. On the right side of the fender wall you will find another fuse box. The blower motor fuse is easy to replace.
How do you tell if a relay is bad with a multimeter?
Will a bad relay still click?
If your starter relay has gone bad, the electrical signal will never make it from the battery to the starter motor. As a result, your engine won't turn over - no matter how many times you turn the key. A faulty relay often produces an audible clicking sound when you turn your car.
How do you tell if a relay fuse is blown without a multimeter?
Put one wire to neutral/common, and one wire on the line side of the fuse. If voltage is present the bulb will light up. Now move the wire from the line side to the load side of the fuse. If the fuse is good the light will come on.
What causes a relay to fail?
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.
How do you check a blower motor fuse?
Use voltmeter or ohmmeter to check for a blown fuse. If you find one, replace it. Start car and see if blower motor works. If fuse blows again, check for loose circuits.
Does a blower motor have a relay?
In a blower motor, the relay supplies the power that allows the fans to circulate warmed air. Essentially an on/off switch, the blower motor relay's reactions start and end the heating process in HVAC systems by controlling the flow of current between the power source and the motor.
How do you check a relay?
The only tool required to check a relay is a multimeter. With the relay removed from the fuse box, the multimeter set to measure DC voltage and the switch in the cab activated, first check to see if there are 12 volts at the 85 position in the fuse box where the relay plugs in (or wherever the relay is located).
Where is the blower motor relay fuse located?
Under the instrument panel, look under the glove box. On the right side of the fender wall you will find another fuse box. The blower motor fuse is easy to replace.
Does a blower motor have a relay?
In a blower motor, the relay supplies the power that allows the fans to circulate warmed air. Essentially an on/off switch, the blower motor relay's reactions start and end the heating process in HVAC systems by controlling the flow of current between the power source and the motor.
How do you test a blower motor with a multimeter?
Turn off your vehicle, set your multimeter to Ohms, and check for resistance between the blower's positive and negative terminals. You may also turn the car key to run without starting the engine, put the cooling system at full blast, and check for DC voltage. If none of these produces a reading, the blower is bad.
How do you test a blower motor with a multimeter?
The blower motor in your car is usually located behind your vehicle’s glove compartment. Disconnecting the positive and negative power supply is the first thing to do. The black wire is normally negative. With your multimeter (Ohm scale), you need to take the positive lead of the multimeter to test the negative black cable.
What is a blower motor relay?
The blower motor relay is the electrical switch that is used to supply the power for the vehicle’s blower motor. The blower motor is the component responsible for pushing air through the vents of your vehicle’s heating and air conditioning systems. Without it, the AC system will not be able to circulate any heated or cooled air.
How do I know if my blower motor is bad?
1. Check the Power. 2. Check for debris Check the Capacitor. Types of blower motors This type of motor blows air at a constant speed. 2. variable-speed motors. This motor blows air at varying speed levels. With the need to maintain comfortable temperatures within your home or vehicle, the HVAC is a vital component to have.
What tools do I need to test the relay on my car?
This relay is used for the PCM, fuel pump, fan motors, and a bunch of other stuff. What Tools Do I Need To Test The Relay? A digital or analog multimeter will work. If you need to buy one or are looking to upgrade, check out my recommendations here: Buying A Digital Multimeter for Automotive Diagnostic Testing.
Below you will find two interesting articles on a similar topic 👇
How is the speed of the blower motor controlled?How do I know if my blower motor fuse is blown?
