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 test a blower motor relay?
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.
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.
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 does the blower relay control?
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 relay?
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.
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.
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.
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.
How do you know if it's the blower motor or resistor?
Typically, if the fan will work on some speeds but not on others, the resistor is suspect. Okay, let's say there's no melting going on, but your fan doesn't work on all speeds. Typically, if the fan will work on some speeds but not on others, the resistor is suspect.
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).
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 relay?
The blower motor relay is generally located in the under-hood fuse box or in the under-dash fuse box. A blown fuse can mimic relay failure. A failed blower motor switch can also give many of the same symptoms.
Is there a fuse for blower 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.
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.
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 relay?
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.
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.
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.
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.
Why is my blower not working in my car?
Find the fuse associated with the A/C blower motor. If the blower motor fuse is still in-tact, your problem is located elsewhere. If the fuse is blown, simply replacing the fuse with an identical fuse of the same amperage rating could get your system working again!
Why is my heater blower not working?
If little air is coming through the vents (hot or cold), then it could be because the blower motor for the fan or a switch or resistor that controls fan speed isn't working. Another cause might be that the electronically controlled “blend doors” that direct air flow are stuck or broken.
Should you replace blower motor and resistor at the same time?
We do suggest that you replace the resistor at the same time. It may not be critical, but this will keep the system more uniform. The issue may even be related to the resistor. If you know that it is not related to the issue, then you do not have to replace it.
How do you know if a relay is working?
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.
Below you will find two interesting articles on a similar topic 👇
What happens when a blower motor resistor fails?How do I know if my heater resistor is bad?
