On some platforms, a faulty blower motor relay will cause the blower not to work at all, which means there will be no airflow from the A/C. On others, the blower won't work on “high blow” but all the other speeds will work. The blower motor relay fails because it regularly deals with high current loads.
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.
A Failed Motor
An HVAC blower motor will occasionally fail due to age, wearing out, or not being cleaned regularly. Symptoms may include strange noises, burning smells, or just plain refusing to turn on. If this happens and the motor is no longer operable, a new blower motor may be needed.
The engine will stop running, and your vehicle won't move or start. Main relay problems could also lead to your engine running for a while or a very short time. Your vehicle might start normally sometimes but not start at all at other times.
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.
Blower Motor Resistor Test
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.
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.
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.
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.
Why Does the Blower Motor Relay Fail? The relay is often partnered with a fuse. If there's a power surge, then the fuse will sever the circuit and prevent the power surge from reaching the blower motor. Like any other relay, the blower motor relay regularly deals with high current loads.
If the cooling fan relay has failed, you may see warnings, such as the check engine light and the temperature warning light, pop up on the dash, but first, you may notice that the A/C stops cooling. More about that in the next paragraph. The check engine light illuminating may indicate a faulty cooling fan 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.
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.
If you need to activate a heavy load, high current device using a small, light load switch – you will need a Power Relay!
Relay Lifetimes
The lifetime of electromechanical relays (EMRs) varies widely depending on the relay construction, with the longest lifetimes being around 100 million operations. Full load life. This is the life of the relay when hot switching a load at the maximum current, voltage, or power rating.
In general, relay burnout is caused by abnormal heat generation around the contact and tends to occur under the following conditions: Contact vibration (ultra-frequent switching) causes continuous arcing and melting of the resin at and around the contacts.
On some vehicles, the engine computer, which is often referred to as the powertrain control module (PCM) monitors the fuel pump relay and its circuit. If the PCM detects a problem, it turns on the check engine light and stores a corresponding diagnostic trouble code (DTC) in its memory.
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.
It's designed to automatically shut off the furnace blower if it overheats. Once the blower cools down, pressing the reset button can help restart the furnace. However, it's essential to understand that not all furnace models are equipped with this feature.
Intermittent Operation
When this happens, there's usually something wrong with either the blower motor itself or with another part of your furnace that controls it. Problems include dirty filters, broken wires, poor voltage supply and faulty limit switch or capacitor.