Blower motor not working

Start by checking fuse 35 40A. If it is good, it is your blower motor resistor.

Subject:
EI05082 - Loss of Blower Motor Speeds Except for Low Speed or Inoperative (Replace Blower Motor Resistor and Resistor Module Connector)

Models:
2004-2006 Chevrolet Avalanche, Silverado, Suburban, Tahoe, TrailBlazer, TrailBlazer EXT
2007 Chevrolet Silverado (Classic) Built Prior to September 1, 2006
2004-2006 GMC Envoy, Envoy XL, Sierra, Yukon, Yukon Denali, Yukon XL
2007 GMC Sierra (Classic) Built Prior to September 1, 2006

with HVAC System AC Front, Manual Temp Control (RPO CJ3) or Heater Only (RPO C42)

Supercede:

This bulletin is being revised to clarify the Warranty Information. Please discard Corporate Bulletin Number 05-01-38-012B (Section 01 - HVAC).

Condition

Some customers may comment that the blower will only work on low speeds or has become inoperative.

Correction

REPLACE THE BLOWER MOTOR RESISTOR AND RESISTOR MODULE CONNECTOR.

Replace the blower motor resistor and module connector using the following procedure:

Remove the blower fuse.

Fullsize Trucks and Utility Vehicles - Htr A/C & HVAC 1 fuses

Midsize Utility Vehicles - Blower Fuse 35 located in the Underhood Fuse Block

Lower the hush panel or close-out panel enough to gain access to the resistor module connector.

Disconnect the connector from the resistor module.

Remove the tape from the wiring harness to expose the wiring.

Cut the wires back far enough from the connector to eliminate any melted insulation on the wire.

Tip

Use the old connector as a map for splicing the wires for the new connector. Be sure to use the correct crimping tool from the terminal repair kit J 38125. Use only Duraseal splice sleeves. Other splice sleeves may not protect the splice from moisture or provide a good electrical connection.

Install the new connector. Use the yellow splice sleeves provided with the connector.

Install new blower motor resistor.

Reinstall the fuse or connector block. Test the blower motor to make sure all speeds are functional.

Reinstall the hush panel/close-out panel.

follow this info and post back with what you find.

Try this, here is a bulletin for this problem.I know I answered this same problem somewere in the trailblazer section, but here is the bulletin. Diagnose for loss of battery voltage to the rear fuse block on circuit 300 ORN for the following fuses:

Note: Prior to proceeding forward with the information below, it is important to verify the voltage as indicated however it is equally important to verify the integrity of each circuit. This can be achieved by performing a voltage drop test or by adding a device to each circuit that will supply sufficient load to verify the circuits integrity.

HVAC 30A, 4WD 15A, HVAC 1 10A, BRAKE 10A, TBC RUN 3A.

Check circuit 300 ORN for battery voltage when the ignition key is in the RUN position.
Check for battery voltage at the rear fuse block under the rear seat Connector C1 pin D9.
If battery voltage IS NOT present at these locations, check for voltage at the ignition switch pin G for circuit 300 ORN.
If battery voltage IS present at the ignition switch pin G, check circuit 300 for an open.
If battery voltage IS NOT present at the ignition switch pin G, replace the ignition switch.
Post back with what you find.

Circuit 300 is the orange wire that runs from the ignition switch to the rear fuse block.(Under the back seat)you are checking for the presents of 12 volts on that circuit. If you have 12 volts than the ign switch is bad, if not you could have a short to ground somewere on that circuit.I would post a picture but it will not let me post one.

Could also be faulty A/C switch. Will have to test blower motor by applying 12v power to motor, if it runs then motor is good.

I think you are right, the control unit is faulty, or you have a relay that is sticking.

-Check the blower motor control module at lower right side of dash-