How do you test a blower motor resistor?
Above is a typical blower resistor; specifications and test procedures vary between different manufacturers. 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.
What happens when a blower motor resistor gets too hot?
If the fan malfunctions (like if the fan shaft is spinning in the blower cage hub without spinning the cage) so that no air is moving past the resistor but current is still creating heat in the resistor pack, the thermal fuse that is integral to the resistor assembly opens the electrical circuit to prevent the resistor (s) from getting too hot.
Can a broken motor switch stop a blower?
A broken blower motor switch can also stop the blower from changing to certain speed settings. If your blower motor cannot change to certain speeds, check both the resistor and the switch on your dashboard. The most common failure points are the resistor and the motor itself.
What to do if your blower resistor Burns?
Look for obvious signs of corrosion and burns from overheating. If you see signs of overheated connectors, replace the blower resistor and its connector, but again, you must splice the wires right, or you’ll have problems at the splice later on.
How can I tell if my blower motor resistor is bad?
A repair manual can tell you where its location is in your vehicle’s make and model. Inspect the resistor visually. Look for obvious signs of corrosion and burns from overheating.
How does an A / C blower motor resistor work?
Blower Motor Resistor Testing. An A/C blower motor resistor uses resistance to control the speed of the blower motor. Many blower resistors control current to the blower motor in all speeds except high. In high speed the resistor is bypassed and power is fed to the motor directly from the switch.
A broken blower motor switch can also stop the blower from changing to certain speed settings. If your blower motor cannot change to certain speeds, check both the resistor and the switch on your dashboard. The most common failure points are the resistor and the motor itself.
How to test vehicle AC / heat blower motor to tell if bad?
How to Test Vehicle AC/Heat Blower motor. When your blower motor goes bad you will not get AC or Heat to blow inside of your vehicle, you will also not be able to defrost your windows. Loading…
When a switch, a resistor, and a load are wired in series, the resistor “drops” some of the voltage passing through it, effectively reducing both current flow and voltage at the motor. A voltmeter connected to both ends of a resistor while current is passing through it to a load will measure the amount of voltage being “dropped” by the resistor.
What to do if your blower motor runs all the time?
If playback doesn’t begin shortly, try restarting your device. Videos you watch may be added to the TV’s watch history and influence TV recommendations. To avoid this, cancel and sign in to YouTube on your computer. A collection of my personal auto repair videos on a variety of car repairing subjects.
How does a relay work on a blower motor?
Finally, with the fan switch on the highest speed, the fan motor is receiving system voltage (14.5 with the engine running). Some systems will energize a relay when the switch is set at the highest fan speed. The relay then closes its contacts, feeding full voltage to the fan, because a relay can handle the current better than the fan switch.
When a switch, a resistor, and a load are wired in series, the resistor “drops” some of the voltage passing through it, effectively reducing both current flow and voltage at the motor. A voltmeter connected to both ends of a resistor while current is passing through it to a load will measure the amount of voltage being “dropped” by the resistor.
Why are there so many resistors on a blower switch?
The blower switch and its gang of resistors are wired so that when the blower switch is set at the lowest speed, the maximum amount of voltage is dropped and the least amount of current is fed to the motor because it is passing through an entire series of resistors – for our purposes we’ll say there are three resistors.
Look for obvious signs of corrosion and burns from overheating. If you see signs of overheated connectors, replace the blower resistor and its connector, but again, you must splice the wires right, or you’ll have problems at the splice later on.
The blower switch and its gang of resistors are wired so that when the blower switch is set at the lowest speed, the maximum amount of voltage is dropped and the least amount of current is fed to the motor because it is passing through an entire series of resistors – for our purposes we’ll say there are three resistors.