At Fixya.com, our trusted experts are meticulously vetted and possess extensive experience in their respective fields. Backed by a community of knowledgeable professionals, our platform ensures that the solutions provided are thoroughly researched and validated.
Re: Take a long time for blower motor to get up to speed
The first thing I would do is to clean motor and squirrel cage. It would be best if you would remove it and take it somewhere that you had a air compressor to blow out motor ports and fins on squirrel cage. Most of the time you can remove by disconnecting modular plugs and removing two or more screws on rail that squirrel cage slids on.
If you can get it out you can use a fine wire brush to loosen dirt and dust from fins on cage then use air to blow out as much as you can.
Your motor may be getting worn so check the bearing by grasping cage and see how much it will slide side to side and if it moves more then about1/8 inch then you are going to need to replace it before much longer. Also make sure that the rim of squirrel cage is not rubbing on blower housing and if it is then loosen motor mounting screws and adjust ,then retighten screws.
I hope this helps you. Thanks
- If you need clarification, ask it in the comment box above.
- Better answers use proper spelling and grammar.
- Provide details, support with references or personal experience.
Tell us some more! Your answer needs to include more details to help people.You can't post answers that contain an email address.Please enter a valid email address.The email address entered is already associated to an account.Login to postPlease use English characters only.
Tip: The max point reward for answering a question is 15.
Probably something going on with the blower motor control Processor . Hooking a scan tool an checking for DTC'S - diagnostic trouble codes would be the first step in a diagnostic procedure for a problem like this .
Auxiliary Blower Motor Control Processor
The auxiliary blower motor control processor is an interface between the auxiliary HVAC control module and the rear blower motor. The auxiliary blower motor control processor monitors supply voltage and ground circuits to the rear blower motor. The auxiliary HVAC control module provides a pulse width modulation (PWM) signal to the control processor in order to command the blower motor speed. The auxiliary blower motor control processor uses the blower motor ground as a low side control to adjust the blower motor speed.
The blower motor forces air to circulate within the vehicles interior. The vehicle operator determines the blower motors speed by placing the blower motor switch in a desired speed position or by selecting automatic operation. In manual operation, once a blower speed is selected, the blower speed remains constant, until a new speed is selected. In automatic operation, the HVAC control module will determine what blower speed is necessary in order to achieve or maintain a desired temperature.
As the requested blower speed increases, the following conditions occur:
• The HVAC control module increases the amount of time that the blower motor speed control circuit is modulated to ground.
• The voltage and duty cycle, measured between the blower motor speed control circuit and ground, decrease.
As the requested blower speed decreases, the following conditions occur:
• The HVAC control module decreases the amount of time that the blower motor speed control circuit is modulated to ground.
• The voltage and duty cycle, measured between the blower motor speed control circuit and ground, increase.
Fuse for rear air ????? No air coming from rear vent's ? That would be caused by the HVAC blower motor not working . Probably not a fuse issue , if the fuse is blown you have a bigger issue . Fuse's don't just blow for no reason - electrical short circuit, too much current draw etc.. . More then likely it's a problem with the blower motor control module or the blower motor . Located behind the right rear trim panel . But go ahead an check the fuse anyway , fuse # 26 - 25 amp located in the underhood fuse / relay box . marked RR -BLWR/ 110 VAC
Auxiliary Air Speed
The auxiliary blower motor is controlled by the front auxiliary blower motor switch. If the vehicle is equipped with rear DVD (U32), the auxiliary blower motor can be controlled by the overhead console, vehicle entertainment system (VES). The front auxiliary blower switch must be in the AUX position in order to control blower speed from the VES. The VES will send a class 2 message to the HVAC control module requesting a blower motor speed.
The auxiliary blower motor control module is an interface between the HVAC control module and the auxiliary blower motor. The auxiliary blower motor speed control, auxiliary blower motor speed signal, blower motor speed control, and ground circuits enable the control processor to operate. The HVAC control module sends the commanded blower motor speed to the control processor through a 0 to 8-volt linear ramped blower motor speed control circuit. As the blower motor speed control voltage increases, the blower motor speed increases. The control processor sends the actual blower speed to the HVAC control module through a 0 to 12-volt blower motor speed signal circuit. The control processor uses the blower motor ground as a low side control to adjust the blower motor speed. The underhood fuse block supplies 12 volts to the blower motor through the blower motor voltage supply circuit.
Which system ?
HVAC Systems - Manual HVAC Systems - Automatic
If automatic it's probably the blower motor control processor .
Blower Motor Control Processor
The blower motor control processor is an interface between the HVAC control module and the blower motor. The blower motor speed control, Blower motor speed signal, battery positive voltage and ground circuits enable the control processor to operate. The HVAC control module sends the commanded blower motor speed to the control processor through a 0 to 12-volt linear ramped blower motor speed control circuit. As the blower motor speed control voltage increases, the blower motor speed increases. The control processor sends the actual blower speed to the control module through a 0 to 12-volt blower motor speed signal circuit. The processor supplies 12volts to the blower motor through the blower motor voltage supply circuit. The control processor uses the blower motor ground as a low side control to adjust the blower motor speed.
This vehicle doesn't have a blower motor resistor ! It has a blower motor control module , if you have automatic climate control !
If manual climate control , then there is a blower motor resistor assembly !
Blower Motor Control Processor
The blower motor control processor controls the speed of the blower motor by increasing or decreasing the voltage drop on the ground side of the blower motor. The HVAC control module provides a low side pulse width modulated signal to the blower motor control processor over the blower motor speed control circuit. As the requested blower speed increases, the HVAC control module increases the amount of time that the speed signal is modulated to ground. As the requested blower speed decreases, the HVAC control module decreases the amount of time that the signal is modulated to ground.
Air Speed - Front Control
The blower motor forces outside air into the vehicle's interior. The vehicle operator determines the blower motor's speed when the driver places the blower switch in one of 5 blower speeds. The blower motor will always operate in any switch position other than OFF, as long as the ignition switch is in the RUN position. The blower motor and mode switches are located within the HVAC control module. The blower motor OFF input is connected in series with the HVAC control module by the off blower motor control circuit.
Depending upon the selected speed, power is provided to the blower motor from either the ignition 3 voltage or battery positive voltage circuits from the fuse block. The battery positive voltage circuit only provides power when the High blower switch position is selected. Power and ground are provided to the HVAC control module by the ignition 3 voltage and the ground circuits.
Low Blower Speed
When the Low 1 blower speed is selected, the HVAC control module applies voltage to the blower motor resistor assembly through the low blower motor control circuit. Voltage is divided between 4 series resistors, a blower relay, and the blower motor to achieve the desired blower speed. The blower motor is grounded through the ground circuit.
Medium Blower Speeds
When the Medium 1 blower speed is selected, the HVAC control module applies voltage to the blower motor resistor assembly through the medium 1 blower motor control circuit. Voltage is divided between 3 series resistors, a blower relay, and the blower motor to achieve the desired blower speed. The blower motor is grounded through the ground circuit.
When the Medium 2 blower speed is selected, the HVAC control module applies voltage to the blower motor resistor assembly through the medium 2 blower motor control circuit. Voltage is divided between 2 series resistors, a blower relay, and the blower motor to achieve the desired blower speed. The blower motor is grounded through the ground circuit.
When the Medium 3 blower speed is selected, the HVAC control module applies voltage to the blower motor resistor assembly through the medium 3 blower motor control circuit. Voltage is divided between a series resistor, a blower relay, and the blower motor to achieve the desired blower speed. The blower motor is grounded through the ground circuit.
High Blower Speed
When the High blower speed is selected, the HVAC control module applies voltage to the blower motor resistor assembly through the high blower motor control circuit. The voltage energizes the blower relay, causing the blower motor to be connected directly to the battery positive voltage circuit. The blower motor and blower motor relay are grounded through the ground circuit.
Go on you tube an check out videos on trouble shooting blower motor circuit Chevy Trailblazer EXT Blower Motor Won Turn Off
Which of these systems does your vehicle have ?
HVAC Systems - Automatic
Blower Motor Control Processor
The blower motor control processor controls the speed of the blower motor by increasing or decreasing the voltage drop on the ground side of the blower motor. The HVAC control module provides a voltage signal to the blower motor control processor over the blower motor speed control circuit. As the requested blower speed increases, the HVAC control module increases the amount of time that the speed signal is modulated to ground. As the requested blower speed decreases, the HVAC control module decreases the amount of time that the signal is modulated to ground.
HVAC Systems - Manual
Air Speed - Front Control
The blower motor forces outside air into the vehicle's interior. The vehicle operator determines the blower motor's speed when the driver places the blower switch in one of 5 blower speeds. The blower motor will always operate in any switch position other than OFF, as long as the ignition switch is in the RUN position. The blower motor and mode switches are located within the HVAC control module. The blower motor OFF input is connected in series with the HVAC control module by the off blower motor control circuit.
Depending upon the selected speed, power is provided to the blower motor from either the ignition 3 voltage or battery positive voltage circuits from the fuse block. The battery positive voltage circuit only provides power when the High blower switch position is selected. Power and ground are provided to the HVAC control module by the ignition 3 voltage and the ground circuits.
Low Blower Speed
When the Low 1 blower speed is selected, the HVAC control module applies voltage to the blower motor resistor assembly through the low blower motor control circuit. Voltage is divided between 4 series resistors, a blower relay, and the blower motor to achieve the desired blower speed. The blower motor is grounded through the ground circuit.
Medium Blower Speeds
When the Medium 1 blower speed is selected, the HVAC control module applies voltage to the blower motor resistor assembly through the medium 1 blower motor control circuit. Voltage is divided between 3 series resistors, a blower relay, and the blower motor to achieve the desired blower speed. The blower motor is grounded through the ground circuit.
When the Medium 2 blower speed is selected, the HVAC control module applies voltage to the blower motor resistor assembly through the medium 2 blower motor control circuit. Voltage is divided between 2 series resistors, a blower relay, and the blower motor to achieve the desired blower speed. The blower motor is grounded through the ground circuit.
When the Medium 3 blower speed is selected, the HVAC control module applies voltage to the blower motor resistor assembly through the medium 3 blower motor control circuit. Voltage is divided between a series resistor, a blower relay, and the blower motor to achieve the desired blower speed. The blower motor is grounded through the ground circuit.
High Blower Speed
When the High blower speed is selected, the HVAC control module applies voltage to the blower motor resistor assembly through the high blower motor control circuit. The voltage energizes the blower relay, causing the blower motor to be connected directly to the battery positive voltage circuit. The blower motor and blower motor relay are grounded through the ground circuit.
HVAC Control Module
The HVAC control module is a class 2 device that interfaces between the operator and the HVAC system to maintain air temperature and distribution settings. The battery positive voltage circuit provides power that the control module uses for keep alive memory (KAM). If the battery positive voltage circuit loses power, all HVAC DTCs and settings will be erased from KAM. The body control module (BCM), which is the vehicle mode master, provides a device on signal. The control module supports the following features:
Bad blower motor resistor - attaches to blower motor and regulates fan speeds. Not uncommon to lose 1 speed at a time until you get stuck with only 1 speed
Bad blower motor
Bad heater control module - less likely but still possible the module is bad and the whole unit requires replacing
Check the blower resistor pack - usually located in the heater air ducting in the blower fan airflow. Check for loose connections and open circuit resistors on the unit.
If speed 4 works always, its unlikely to be the blower motor ground connection.
×