Heat Stopped Working In My Car! Blower Motor or Resistor?

Did your heater stop working? Or your AC? Chances are it's your blower motor, or it
could be your resistor. That's what we're gonna talk about in this
video. So, you've confirmed that your heat or AC
is not working. You've turned the key on. You've checked the heater controls. Nothing's happening. First thing we want to do is check the fuses. All right. We want to check our test light first. Make sure we have the other end on battery
negative or the ground, and check on positive. So, it works. Now, you're gonna want to check your owner's
manual to check where your fuse is. So you can check the fuse on one side, and
then check the other side. And as long as the test light lights up, then
the fuse is good.

Or you could pull out the fuse and take a
look. There is little holes on the fuse, on the
back side of the fuse that gives you the ability to test it with a test light. So if your fuse is blown, just put a new fuse
in it. You should be all set. Mm…not really. There's probably something else wrong with
the vehicle. But let's say the fuse is good. Let's check out the blower motor. So, you want to locate your blower motor. The blower motor generally is underneath the
dash on the passenger side. And then, disconnect the connector. Every blower motor needs power and ground
to work. That's what we're gonna test for. Make sure your key and your heater switch
is turned on before you start this test. So, we can test this connector. Find something metal. So, we have power there. Now, if you were to check for ground, we would
want to put this end on battery positive. So you'd go to the battery on the positive
terminal, and then check the other end. So, you have power and ground at the connector,
that means everything in front of that connector is working.

The problem is with the blower motor, and
it needs to be replaced. So if you didn't have power there, or you
didn't have ground there, the next step, we're gonna test the resistor. The resistor is what controls the blower motor
speed by restricting electricity through either the ground or the positive side of the circuit. So, this vehicle actually has a resistor module. That's a little bit different than a regular
resistor. It's gonna be close to where the blower motor
is, and we have four wires going into this. We have one wire right here that is the blue
wire, it's gonna be the power wire going into the module. This black wire right here is gonna be the
ground wire going into the module. And then this lighter blue color, thinner
wire is the signal wire.

That comes from the switch itself. That tells the module what to do. And then, this green and black wire goes to
the blower motor, and that's gonna vary the ground signal. So, what we can do is disconnect this, disconnect
that. The back side has a heat sink. That's to keep it cool. We have our test light. We have it hooked up to a ground on the other
end. With the key on, I can test for power there. We have power there. That's good. Now I have the other end of the test light
attached to battery positive. Now let's check this ground, and that lights
up, so that ground is good. Now I'm gonna test the signal wire to make
sure that everything that is getting to the module needs to get to the module to make
it work. So for this vehicle, this signal switch actually
changes the ground signal. So to test the ground signal, I'll put the
positive terminal on the blue wire, which is battery positive, and this ground wire
to that signal wire, And then we can vary the switch.

As we change the switch we can watch the voltage
change. It's gonna go up. Now, every vehicle is gonna be a little bit
different, and it's gonna be hard to find these readings in different repair manuals
and stuff. As long as you see the voltage changing, then
you're gonna know the switch is most likely working properly. Now, if this resistor was working properly,
this was plugged in, what you could do is check the circuit on this side, and have the
other side of the test light on battery positive. We're gonna vary the switch. Because we changed the switch, we can watch
the light go from dim to bright. So, that is varying the ground signal and
sending it to the blower motor. That's how a good resistor would look.

So, if the resistor or resistor module is
not getting what it needs to, to vary the speed of the blower motor, there may be another
issue with either the wiring or the switch itself, or even a relay. So, sometimes you're gonna need a blower motor,
sometimes you're gonna need a resistor. Certain instances you're gonna need both. If the blower motor itself, when it's getting
its power, is having a lot of trouble, if the motor itself is tired inside, the brushes
aren't doing their job as well, it's gonna put a lot of strain on the resistor. And the resistor is gonna get hot. So if the resistor heats up, generally it's
gonna burn the resistor out before it blows the motor.

So when you go to replace the resistor, you're
gonna have a brand new resistor in there, getting really hot. After a month or two, it may burn your new
resistor out. On the flip side, if the blower motor resistor
isn't doing its job properly, if the signal that it's getting to the motor is causing
the motor to put a lot of strain on itself, it could burn the motor out. Not as common as the other way around. So, if you have a bad blower motor, chances
are the resistor's not far behind. If you have a bad resistor, chances are it's
due to the blower motor, so it's a good idea to replace them both at the same time.

Thanks for watching. Visit 1AAuto.com for quality auto parts shipped
to your door. The place for DIY auto repair. And if you enjoy this video, please click
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