Location of the blower motor control module

Are the heater hose from the engine compartment going to the fire wall hot to the touch ? Is the HVAC - heating , ventilation an A/C system manual or automatic ?
Control System Inputs-Manual A/C
Climate Control Assembly
The climate control assembly has three system controls:

• The A/C heater function selector switch combines a vacuum selector valve with two electrical switches to supply battery voltage (B+) to the A/C clutch circuit and the blower motor speed control circuit.
• Temperature selection is accomplished with a potentiometer connected to the electric blend door. Movement of the control knob from COOL (Blue) to WARM (Red) causes a corresponding movement on the air temperature blend door and determines the temperature that the system will maintain.
• The blower motor switch controls blower motor speed by adding or bypassing resistors in the heater blower motor switch resistor.

Control System Outputs-EATC
A/C Blower Motor Speed Control
The A/C blower motor speed control is located on the A/C evaporator housing, in the engine compartment.

• The function of the A/C blower motor speed control is to convert low power signals from the electronic automatic temperature control module to a high current, variable ground feed for the blower motor.
• Blower motor speed is infinitely variable and is controlled by the electronic automatic temperature control module software.
• A delay function provides a gradual increase or decrease in blower motor speed under all conditions.

A/C Electronic Blend Door Actuator
The A/C electronic blend door actuator is located on the top of the plenum housing.

• Its function is to move the air temperature blend door on command from the control assembly.
• The A/C electronic blend door actuator contains a reversible electric motor and a potentiometer. The potentiometer wiper is connected to the actuator output shaft and moves with the output shaft to indicate the position of the air temperature blend door.
• A 5 volt signal is applied to the ends of the potentiometer. The voltage available at the wiper indicates the position of the potentiometer. The expressed value of the actuator wiper voltage is sent to the electronic automatic temperature control module and is matched with the wiper voltage of the module potentiometer. The control module then drives the actuator motor in the direction necessary to make the actuator wiper voltage agree with the control module wiper voltage.

Doesn't work on any speed ? high - low . Does your's have manual or automatic climate control ?
Don't think a fuse problem , blower motor control processor more then likely .
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, battery positive voltage, and ground circuits enable the control processor to operate. The HVAC control module provides a pulse width modulation (PWM) signal to the control processor in order to command the blower motor speed. The processor supplies 12 volts 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.
Look here for fuse location an wiring diagram's http://www.bbbind.com/free_tsb.html Enter vehicle info. year , make , model an engine size. Under system click on HVAC , subsystem HVAC controls . click the search button then click on the 5th blue link . This show's fuse location an wiring diagram for the blower electrical circuit . If you don't know where the rear fuse box is ,it's under the rear seat . It would be easier to just check under the passanger side dash at the blower motor control processor at the orange wire .
Do you know how to test electrical circuits with a voltmeter ?

GMC Yukon HVAC Blower Motor Won Turn On

A/C - Heater blower motor ! What make , model and year vehicle ? Manual or automatic climate control ? Could be a bad blower motor control module , a high blow relay contacts stuck closed .

Automatic or manual climate control ?

• The blower motor does not operate correctly - manual climate control

• Circuitry short
• A/C blower motor resistor
• A/C blower motor switch
• Blower motor high speed relay

• Go To Pinpoint Test O .

• The blower motor does not operate correctly - EATC

• Circuitry short/open
• A/C blower motor speed control
• EATC module

• Go To Pinpoint Test Q .

Pinpoint Test Q: The Blower Motor Does Not Operate Correctly - EATC
Normal Operation Under normal operation, the blower motor control module receives a 1-2 volt signal from the EATC module through circuit CH218 (GN/VT) to determine the desired blower motor speed. The EATC module receives a feedback voltage from the blower motor control module through circuit VH219 (GY) to determine actual blower motor speed. When the highest blower motor setting is selected, the EATC module sends 12 volts to the blower control module through circuit CH217 (BN).

Possible Causes
• An open, short to voltage, ground or together in circuits CH218 (GN/VT), VH219 (GY) or circuit CH217 (BN)
• Blower motor control module
• EATC module
• If automatic HVAC system i would suspect Blower motor control module .

Automatic climate control? The HVAC control module is the part with the buttons that control the heater in the dash.

The first thing I would do is access the blower motor. With key on and/or the engine running wiggle the connector at the blower motor. It you get the same symptom than replace the blower motor. I run into quite a few of these with this symptom.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

If the blower motor only works on high mode, then its problem with blower motor resistor. ------------------ The blower motor resistor needs to be replaced.This will make blower motor work on all modes. ----------- Thanks.

I am going to assume that you have the Automatic climate control on your car. it gives you an auto fan mode, and temperature options. Often the problem does not lie in the blower motor, but rather, the climate control module. Often, the blower motor only works on Auto fan mode, or on full out. It will often also only operate in certain modes, such as only in defrost mode, or panel. I have had several town cars and Grand Marquies of these era's and have had the same problems with 2 of these cars. The only good solution to the issue is to replace the climate control module, which is the panel with all of the switches for the heater controls. If you're really adventurous or cannot find the replacement part, it may be possible to hard wire the fan to a multi resistance switch, but you really got to know what you're doing.

disconect the negative battery cable from battery for 20 seconds and replace cable back,then try ac let me know if this helps u

replace the blower motor speed control module, that is the only cause of this problem that I know of, and u are about the 20 post for this issue that I have read, it has fixed the other ones..

if you have manual control climate control then the system has a blower motor resistor . if you have automatic climate control then the system has a blower motor speed control. in eather case the part is under the dash in the heater box. depending on the system you have, buy the part and then look under the dash for like part, you will half to remove the under dash panels to be able to see. the part will be on the heater box somewhare.