In the highest speed state, the blower resistor is bypassed completely
and the fan is connected directly to the car's battery, which allows maximum current through the motor.
What causes heater resistors to burn out?
By it's very nature, resistors resist the flow of electricity, much like a flow restrictor in a pipe. However,
as a side effect of reducing current flow
, resistors generate heat. Over time, that heat can cause the resistor to fail naturally.
What happens when a blower motor resistor fails?
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.
How do I know if it's the blower motor or the 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 fix a block resistor?
What does a final stage resistor do?
The final stage (or blower motor) resistor
controls the speed of the blower motor in your heating & air conditioning system
. Faulty resistors can cause a list of erratic issues, from the fan running when the car is off, to only having one fan speed available.
Can I bypass a resistor?
All current will bypass the resistor
and travel through the short. The voltage across the 100Ω resistor is going to be zero. The 100Ω resistor is not impacting the circuit.
Why does the blower motor stopped working?
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.
How do you know if your heater resistor is bad?
- Fan does not work at all, so no air comes out of the vents.
- Fan only works on some speeds and not others.
- Fan only works on the highest speed.
- Fan runs all the time and can't be controlled with the fan switch.
- You see smoke coming out of the vents.
How much does it cost to replace blower motor resistor?
The average cost for blower motor resistor replacement is
between $109 and $140
. Labor costs are estimated between $44 and $55 while parts are priced between $65 and $84. This range does not include taxes and fees, and does not factor in your specific vehicle or unique location. Related repairs may also be needed.
Can a bad blower motor resistor cause no heat?
Problems with Your Blower Motor or Blower Motor Resistor
The blower motor resistor is the part that controls the fan speed of the blower motor.
Both of these components can fail, resulting in the heating system simply not working
.
Where is the heater blower resistor located?
The heater blower motor resistor is often found
beneath the dashboard
. It is located in the heater and air conditioning compartment. It's connected to the air conditioning system, where it can adjust the speed of the blower motor fan. It can also be found behind the glove box of some vehicles.
Why does my heater only work on high?
Resistor module replacement
Most car manufacturers use a series of resistors to make the heater blower motor run at different speeds. And when one or more of these resistors burn out, you're usually left with only one heater blower motor speed—high. The resistor module is easy and inexpensive to replace.
What is a bad resistor?
A bad resistor will
either show infinite resistance or a measurement far higher than its rated resistance
. In either case the resistor is no longer functioning properly.
Should I replace blower motor and resistor?
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.
Is there a fuse for the heater blower?
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 replace a blower motor resistor?
Locate the blower motor resistor on the passenger side under the dash board. It is mounted to the the blower housing near the blower motor. Disconnect the electrical connector to the blower motor resistor. Remove the screws or bolts to the blower motor resistor and remove the resistor.
Are all blower motor resistors the same?
Blower motor resistors have several resistors with different resistances
. This controls the current that runs through the blower motor. Each fan speed selection is connected to one or more of the resistors in the blower resistor assembly.
How do you make a resistor block?
How do I test a fan resistor?
How do you check the final stage resistor on a BMW?
What is final stage unit BMW?
The blower final stage fan resistor also goes by the name of the blower motor resistor. This component is
an electrical part responsible for providing the voltage to the fan that controls the heating and air conditioning in your BMW
. You can find a blower motor resistor in BMWs that have 4 or 5 fixed speeds.
What happens if a resistor is shorted?
A shorted resistor (resistance of 0 Ω) would
theoretically draw infinite current from any finite source of voltage
(I=E/0). In this case, the zero resistance of R
2
decreases the circuit total resistance to zero Ω as well, increasing total current to a value of infinity.
What causes resistors to fail?
A fixed composition resistor normally fails in an open configuration when
overheated or overly stressed due to shock or vibration
. Excessive humidity may cause an increase in resistance. A variable composition resistor may wear after extensive use, and worn away particles may cause high resistance short circuits.
How do you know if a resistor is shorted?
If you don't see any resistors across a line then you don't need to change the node name. As you can see,
both ends of the 5-Ohm resistor has “a”, so it's shorted out
.
