What does the heater blower resistor do

The blower motor resistor in your car is the part that is responsible for pushing air through the vents when using the air conditioner or heater. The blower motor resistor is constantly put under stress which can cause it to eventually fail.

How do I know if my blower motor resistor is bad?

1. Only One Speed From Blower Motor. One of the most common symptoms of trouble with the blower motor resistor is when the fan gets stuck in one setting. …
2. Various Airflow Settings Not Working. …
3. No Air Coming From Vents.

What is the purpose of a blower motor resistor?

The blower motor resistor is responsible for controlling the blower motor speed. In the past, this was done by varying the voltage supplied to the blower motor. In newer applications, the blower motor resistor is actually a solid state module that sends a varied signal to the blower motor.

What happens when blower resistor goes bad?

Problems with a blower motor resistor are common in many cars. The most common symptom of a failed blower motor resistor is when the heater fan only runs at the highest speed setting (4 or 5) and doesn’t work at low speeds. In some cars, a failed blower motor resistor can cause a heater fan to stop working completely.

What are the symptoms of a bad blower motor relay?

If you have a faulty blower motor, you may experience low airflow from the vents, even when the fan is on high. There will be no air coming from the vents if your fan isn’t working due to a bad blower motor resistor.

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.

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.

Is there a fuse for the heater blower?

The blower motor is powered by a fuse-like device called a relay. If your heater or air conditioner does not blow air through the vents, this could indicate that the blower motor fuse has probably blown. While replacement is easy, the exact location of your blower motor fuse may vary from vehicle to vehicle.

How do you know if a resistor is bad?

Your meter will read it as open circuit (infinite ohms). Or maybe it’s a 0.1 ohm current sensing part. Your meter will read it as a short circuit. If it’s a larger resistor with leads and it looks and smells burnt, assume it’s bad.

How do I test a blower motor 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.

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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.

What components should be checked if a blower motor resistor is found to be defective?

• 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.

Why will a blower run on the on position and not on auto?

Other Blower Fan Won’t Run Problems The fan will run and blow warm air but only in FAN or FAN ON mode – delivering heat – but NOT in AUTO mode. This is a bad temperature sensor in the unit; replace the fan limit controller.

Does the blower motor resistor control heat?

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. … A failed blower motor resistor can cause issues with the operation of the entire heating and air conditioning system.

Can you test a blower motor resistor with a test light?

Unplug the blower motor and test for power using the 12-volt test light in the same manner as explained in Step 1. … If there is power indicated on high blower speed, but not low or mid range, the problem is the blower resistor.

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.

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.

How often do resistors fail?

Failure mode also depends on the resistor style. As a rule, film styles are most susceptible to resistance drift while wirewounds usually fail in the open circuit mode. Resistors failing in the short circuit mode are rare and only accounting for 3 to 9% of all resistor failures.

How do you know if a resistor is shorted?

If its two terminals are connected to the same node, the resistor is short-circuited. In practical circuits, we might also say a resistor is short-circuited if a much lower value resistor is connected in parallel with it.

Why is my heater not blowing hot air?

The Furnace Is Blowing Cold Air First, check to make sure the thermostat is set correctly. You will want to make sure that the fan control is set to auto, and not ‘on’. If the thermostat appears set correctly, turn off your heater at the thermostat and check the filter. If the filter is dirty, replace it.

Why is my blower not working in my car?

If little air is coming through the vents (hot or cold), then it could be because the blower motor for the fan or a switch or resistor that controls fan speed isn’t working. Another cause might be that the electronically controlled “blend doors” that direct air flow are stuck or broken.

Does a blower motor resistor have a fuse?

A fuse is often located on the resistor board. The fuse only protects the low and medium blower speeds.

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.

What could cause a fuse to keep blowing?

First, and most commonly, when too many lights or plug-in appliances draw power from the circuit, it can overload the capacity of the fuse and cause the metal ribbon inside the fuse to melt through. … A mis-wired lamp, for example, can cause a short circuit and blown fuse if it is plugged into an outlet.

Why does my 5 amp fuse keep blowing on my furnace?

Your thermostat wires or something in the heating circuit are going to ground. Since it works fine when you jump it at the furnace the problem is in the thermostat wire. Since the cooling works fine the problem is in the heating wire (usually W or white).

Does the fan have to be on for the heater to work?

Keeping your fan on AUTO is the most energy-efficient option. The fan only runs when the system is on and not continuously. There is better dehumidification in your home during the summer months. When your fan is set to AUTO, moisture from cold cooling coils can drip and be drained outside.

Why is my furnace fan not turning on?

Start by turning the furnace off, turn your thermostat to “fan only,” and wait a few minutes. If you see or hear the fan turn on, your blower motor is not the culprit. If the fan does not start, you have a wiring issue (circuit breaker trips) or motor problem (circuit breaker does not trip).

Why is my air conditioner running outside but not inside?

A jammed or clogged condenser coil could be the cause of your air conditioner running but not dropping temperatures inside. The condenser fan pulls air into the outside device through the condenser coil to extract heat energy from your home while it’s working properly.

How hard is it to replace a blower resistor?

How to Replace a Blower Motor Resistor. The blower motor resistor is usually extremely easy to access, but the hard part can be positioning your body inside the car to remove the part.