Common causes include electrical problems, a malfunctioning blower motor, or thermostat-related issues. Electrical problems may include blown fuses within the furnace circuit or tripped circuit breakers in your electrical panel. If the blower motor is worn out or has failed, it can cease to function altogether.
When you have NO speeds, it's probably the motor, but could be the blower speed switch or fuse. Check the fuse and test for voltage at the motor, and replace the motor if it's getting power but won't spin.
A defective ground wire or ground wire connection and an open circuit in the power-side circuit (including the fuse, wiring, and fan switch) are the most common reasons why a blower motor fails.
The thermostat is what tells these separate systems to work together. In normal operation, when your thermostat is set to "auto," it will tell the blower fan plus the heating or cooling components to turn on and off at the same time when the desired temperature is reached.
Signs of a bad AC capacitor include humming noises coming from the unit, slow starting or stopping of the fan motor, and frequent cycling on and off. AC capacitor troubleshooting should begin with checking for any visible signs of damage such as bulging capacitors or leaking fluid.
A faulty capacitor stops the blower. Check your capacitor soon if your unit stops operating. Make sure the fuse that controls the heating system is turned on before proceeding. Turn increase your thermostat once the furnace is powered up and see if your blower starts to work within a few minutes.
Blower Motor Resistor Test
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.
In most newer systems, the button is often directly next to the blower motor, while in older systems, it may be harder to spot as it is sometimes underneath or behind the motor. The reset button is often made of yellow or red plastic and marked with a large “R ” to make it easier to spot.
Replacing a furnace blower motor costs $560, on average. Depending on the size and type of motor, most people pay $300 to $900. The average blower motor replacement cost is $560, but the final price depends on labor fees, as well as the cost of the parts.
On some platforms, a faulty blower motor relay will cause the blower not to work at all, which means there will be no airflow from the A/C. On others, the blower won't work on “high blow” but all the other speeds will work. The blower motor relay fails because it regularly deals with high current loads.
The most common reason why your blower motor won't work on any speed is that you have a bad or blown a fuse.
One of the most prevalent factors that can cause a blower motor to stop working is a blown fuse. A fuse prevents electrical circuits from an excessive flow of current that may run in them. Over time or due to any sudden surge, it might blow the fuse and cut power to the blower motor.
Either it's not getting electrical power or, more likely, the motor itself has simply burned out. A blower motor in an older vehicle is likely to burn out over time, and may need replacement.
The average cost for a Blower Motor Resistor Replacement is between $119 and $154. Labor costs are estimated between $43 and $54 while parts are priced between $76 and $99. This range does not include taxes and fees, and does not factor in your unique location. Related repairs may also be needed.
Ensure the capacitor attached to it is good – whether you do it before you jump out the blower motor or not, quickly check the capacitor to see if it meets manufacturer specs. If it doesn't, replace it and retest. 3. Make sure the motor isn't getting too warm to the touch – Some motors just get old and dirty.
In AC systems, the air conditioner reset button is on the outside unit's lower edge, typically close to the ground. Some models have the reset button located behind the service panel, which may require tools to remove. Reset buttons are usually red or yellow with a clear “reset” label.
The fan limit switch controls when the furnace blower fan turns on and off. This control also provides a safety limit that turns off the burner or furnace if temperatures at the furnace get too high. Fan/Limit switches are used on all types of heating furnaces.
Blower motor is fuse 35 and is a 40 amp. You could test them with a meter or visually look to see if they're blown, then take it to a shop if they blow after replacing them.
When high speed is requested, the blower motor resistor is bypassed and the blower motor ground circuit is connected directly to ground. This allows the maximum current through the blower motor and maximum speed occurs.
The Blower Motor Is Slow or Inconsistent: A failing capacitor can cause the blower motor to run slowly or fluctuate in speed. The motor can also overheat, short cycle, or run erratically. Call a professional if any of these issues occur.
Although your unit may continue to run, it is not wise to continue using the air conditioner before replacing a failing capacitor as it can lead to compressor failure and fan motor issues as well as system failure.
DIELECTRIC BREAKDOWN (SHORTS)
The classic capacitor failure mechanism is dielectric breakdown. The dielectric in the capacitor is subjected to the full potential to which the device is charged and, due to small capacitor physical sizes, high electrical stresses are common.