Loss of voltage at blower motor when it is connected to regulator

I have a complete loss of voltage when I connect the blower to the resistor – resistor, blower brand new – blower works when attached to battery, voltage at the resistor is between 10.7 and 12.5 when car is running but as soon as I attach the blower motor to the resistor, it drops to zero. Tried connecting blower direct to wires from switch, which had voltage, bypassing resistor, but the voltage still drops to zero.
My car has an automatic transmission.
Experienced mechanics share their insights in answering this question :
Hi there. The issue you are having is not the resister, but rather the switch. The switch contacts are shorting out back to the battery causing the a/c blower not to work. I recommend replacing the a/c blower switch. If you need further assistance troubleshooting your vehicle, then seek out a technician, such as one from YourMechanic, that can assist you with replacing the switch.

How to Identify and Fix Common car Problems ?

Our sources include academic articles, blog posts, and personal essays from experienced mechanics :

How many volts should a blower motor receive? A blower motor should receive between 12 and 24 volts of power in order to operate properly. If the voltage is too low, the motor will not be able to start or run properly. Too much voltage can damage the motor.
The most common reasons a Saab 9-3 heater isn`t working are a broken heater blower motor, a problem with the thermostat, or a failed heater blower motor resistor. Search our network of RepairPal Certified shops near you to speak with a technician about your issue.
Voltage drop testing can be used to determine the health of a circuit. When the blower motor is running at full speed (the lowest amount of resistance running through the blower motor resistor) voltages should not drop more than 0.5-volts.
Electric Air Blower Planet Power, Model: EBC40, 220-230 Voltage.
The blower motor relay is the electrical switch that is used to supply the power for the vehicle`s blower motor. The blower motor is the component responsible for pushing air through the vents of your vehicle`s heating and air conditioning systems.
Blower resistors are resistors which are used to control the fan speed of automotive blowers. The fan speed can be changed either by switching the blower resistor resistance mechanically using a rotating lever, or electronically by the air conditioning system.
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.
A fuse is often located on the resistor board. The fuse only protects the low and medium blower speeds. High speed will still work if the resistor fuse is blown.
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The 9-3 has issues with corroded wiring, which can cause the failure of both the anti-brake system and the traction control. This makes driving, especially on wet surfaces, dangerous. The 9-3 also has a porous engine block, which leads to excessive coolant loss.

Faulty heater cores and low or contaminated coolant levels often come hand in hand, and both issues may lead to your engine overheating and your heater not blowing hot air.
When corrosion, loose connections or other types of resistance restrict a circuit, volts and amps both drop. If volts drop, amps drop too. That is why when you find a voltage drop in a connection or cable, you know the connection or cable is restricted.
In general, satisfactory motor performance requires a voltage within ± 5% of its rated nominal value in steady-state operation, Starting current of a motor can be 5 to 7 times its full-load value (or even higher). If an 8% voltage drop occurs at full-load current, then a drop of 40% or more will occur during start-up.
An acceptable reading for most circuits other than fuel management systems (injectors, sensors, etc.) is less than 0.400 volts, although 0.100 volts or less is preferred. Some starter circuits can allow up to 0.500 volts during a voltage drop test. Anything higher than these values indicates a need for repair.
The voltage range that may be applied to the fan to assure satisfactory operation is dependent upon the individual fan design and may be as small as 10-14V for 12V units and up to 12-56V for 48V units.
Most ceiling fans, as well as most household appliances, use AC motors, as AC is the type of current distributed by power companies. AC motors function by being connected directly to a power source. This power source is what creates the moment of force required to rotate the motor`s rotor.
The blower motor resistor controls the power to the system`s blower motor. When it fails, it can cut off all power to the motor. When the blower motor doesn`t get power, air pressure can`t be produced. You are left with a heater or air conditioner with nothing coming out of the vents.
The blower motor is the electrical switch on the interior of a vehicle that allows the driver to control the vehicle`s heating and air conditioning system. It is usually built into the the same control panel that houses all of the AC system controls, and is labeled with numbers and symbols to indicate blower fan speed.
To decrease the blower speed, you do the opposite rotation. Slightly loosen the setscrew, and then turn the pulley counterclockwise one or two rotations. After, make sure to tighten the setscrew.
The most common airflow control strategy for centrifugal fans is the outlet damper. Sitting right on the outlet of the fan, this is an opposed blade-style outlet damper. We control the flow by incrementally closing the blades to reduce the airflow volume while raising static pressure.
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.
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 Many Ohms Should A Blower Motor Have? A good blower motor is expected to read over 0.5 Ohms.
To test the fan motor, you will need a multimeter. Set the multimeter to the ohms setting and touch the probes to the two terminals on the motor. If the reading on the multimeter is infinite, then this means that there is an open circuit and the motor is defective.
These are different components. The blower motor high relay will affect high speed blower operation. The blower motor resistor will vary the lower speeds.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

Loss of voltage at blower motor when it is connected to regulator – regulator is brand new
ANSWER : Hi there. The issue you are having is not the resister, but rather the switch. The switch contacts are shorting out back to the battery causing the a/c blower not to work. I recommend replacing the a/c blower switch. If you need further assistance troubleshooting your vehicle, then seek out a technician, such as one from YourMechanic, that can assist you with replacing the switch.

How do I install my new blower motor 2006 Nissan Sentra? The new part came with just wires, how do I install a connector?
ANSWER : You must be using an aftermarket blower motor. You will need to cut off the old connector and using wire splices you will need to connect the wires to your connector. Before making final connection you will need to install the motor and hook up wires and make sure motor is running in the correct direction of blowing air out of vents. Then make final wire connection crimps and tape up wires.

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ANSWER : Hi Johnny. About 90% of the time, the problem is the resistor as opposed to the blower motor. A professional mechanic would complete an electrical test to determine if power is being sent through the resistor to determine which one is the issue. If you want to eliminate the guess work, you could have one of our mobile mechanics come to your location to complete an AC is not working inspection so they can determine for you which is damaged and recommend the right repairs.

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ANSWER : Hi there – most likely, the problem is the blower motor resistor pack. A quick way to test this is if the blower fan still works in the "Max" position. If it does, that pretty-much rules out the motor as the problem. The resistor pack can get pretty hot while running the fan in lower settings, which could damage the wiring to it just from the heat. If the resistor shorts, increased electrical load could burn the wiring insulation as well. I would suggest an electrical inspection by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, give you an accurate assessment of damage and cost estimate for repairs.

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A crank but no start condition can be caused by many things. A few common causes are a faulty crank position sensor, or issues with the fuel system. The crank position sensor is used in the engine’s fuel calculations, and in some cases it’s failure will disable the engine.

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I would start by trying to determine if the engine is getting fuel and then going from there. If you need assistance with these checks, consider YourMechanic, as one of our mobile technicians can come to you in order to diagnose your starting issue firsthand for an accurate repair.