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. … Remove the screws, and swap out the resistor module.
Why does my heater pilot keep going out? water heater pilot light goes out randomly.

Why does my heat only work on the highest setting?

The blower motor resistor is prone to shorts, corrosion, and overheating. When the resistor fails, typically, the highest setting is the only option that still functions. This is because the air from the blower motor is bypassing the resistor, thus gaining the maximum amount of voltage, resulting in full power.

What is the primary cause of a blower motor that only operates on its highest speed?

A bad blower motor resistor can cause your blower works on high speed only. Older style blower motor resistor with exposed resistor elements. The blower motor resistor is what’s responsible for giving you three blower speeds. The resistor block contains three different high resistance coils.

What are the signs of a bad blower motor resistor?

  • Blower motor stuck on one speed. …
  • Blower motor does not work on certain settings. …
  • No air from the vehicle’s vents.
Why does my air only work on high?

When a blower resistor fails, the highest fan speed usually is the only one that still works because it essentially bypasses the resistor and receives the maximum amount of voltage. When the resistor is working, it reduces the amount of voltage going to the lower fan speeds, so the fan runs slower.

How much is a blower resistor?

The average cost to replace the blower motor resistor at a repair shop is between $44 and $55 in parts and $70 in labor costs, for a total cost of around $114 to $125.

How do you test a fan resistor?

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. Move the lead from terminal 2 to terminal 3 and check this reading against specifications.

Why does my blower motor resistor keep burning out?

Trent, one of the biggest reasons for blower motor resistors to have shorten life is actually because of faulty blower motor drawing too many amps, some times melting wires/plugs, heating up resistors shortening their life.

Is it the resistor or the blower motor?

The blower motor resistor is an electrical component that is a part of the vehicle’s heating and air conditioning system. It is responsible for controlling the blower motor’s fan speed.

Why does my AC not work at high speeds?

The A/C thermal expansion valve (TXV) most likely is the cause of the A/C system freezing up at higher engine or vehicle speeds. … The A/C system should be performance tested and checked for pressures to make sure the system has enough refrigerant or the TXV is the cause of the problems.

Is there a fuse for 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.

Where is the blower resistor?

It’s located inside the dash, often on the opposite side of the steering wheel or inside the engine compartment on the firewall. A blower motor resistor or a blower motor control module is the part that controls the speed of the blower motor.

How do you know if a resistor is bad?

A good resistor should test within its rated range. 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.

What does a resistor do on a cooling fan?

The purpose of the cooling fan resistor is to remove heat from the engine’s coolant and from the A/C refrigerant. The resistor does this by drawing air through the radiator and air conditioning condenser.

Can a blower motor resistor be bypassed?

Blower resistors are made of several resistors with different resistances. … 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 would cause a resistor to burn up?

Burning of Resistor When a resistor has been overloaded with voltage exceeding its power rating, the resistor will become very hot to touch, darken considerably and possibly even melt or catch on fire.

Why does my car AC blower only work on high?

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.

Can you 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.

Is a switch a resistor?

We can think of the switch as a resistor of either 0 or infinity resistance, so it too can be labeled with a current arrow and a voltage polarity.

How do you know if your heater control module is bad?

  1. Overheating AC parts. One of the first signs that the AC control switch may be having a problem is that certain parts of the AC may overheat. …
  2. Certain settings not working or working intermittently. …
  3. AC compressor not coming on.
What does a blower control module do?

An A/C fan control module helps to control the blower that supplies air to the cabin of a vehicle, as well as the cooling fans. The module helps to make sure that the cool air that is produced within the A/C system of a car is blown into the cabin.

Why does my AC only get cold when I accelerating?

That would usually indicate one of the switches kicking the compressor out for some reason. The heat the AC pulls out of the car gets dumped to the atmosphere by the condenser coils in front of the radiator. This happens much more effectively if you’re moving and air is flowing over the condenser.

Why does my AC cut off when I accelerate?

Typically this occurs due to a bad vacuum check valve under the hood. During hard acceleration the AC door system loses vacuum, causing the doors to default to the windshield. This check valve keeps this from occurring.

Why does my AC only work when I'm driving?

While you’re driving, the compressor spins faster so the high pressure side becomes more pressured and the low pressure side loses some pressure. This means more expansion and more cooling.

Where is the blower motor relay located?

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.

What is blower motor 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 does my blower motor fuse keep blowing?

Blown fuses 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.

Why does my blower motor work sometimes?

When a blower resistor fails, the highest fan speed usually is the only one that still works because it essentially bypasses the resistor and receives the maximum amount of voltage. When the resistor is working, it reduces the amount of voltage going to the lower fan speeds so the fan runs slower.