2004 Silverado Blower Control

[fishermn]

Lost speeds 1 -4 on my blower control. 5 still works, so I am assuming I probably have a failed resistor assembly.

Does this sound right for this vehicle? Also am wondering where the resistor is located on this vehicle. I am really hoping its not in the same place as the one I replaced on my 95 GMC 3500. The resistor on that unit was inside the ducts, but could only be accessed from behind the glove box. It was a serious pain in the rear to get to.

Any advice would be appreciated!

[Jeremy airjer W]

Sound like you are on the right track. It is near the blower motor right above the passenger feet area if I recall correctly.

Here, an article I did a while back on how to check them.

There has been a lot of questions lately about blower motors not working. I thought I would post a basic diagram with some tips on how to figure out whats going on.

The diagram is generic and loosely based on GM's setup and more specifically a Silverado. Most manufacturers have a similar setup and the only major differences would be a ground side control (instead of the switch supplying power to the resistor it would be grounding the power from the resistor if this is the case you test light would need to be connected to power to test the switch) and late model Chrysler minivans (they use a module that looks for a difference in a/c voltage from the switch)

If the blower works on high only than likely the resistor assembly is the culprit since power to the blower essentially bypasses all of the resistors and/or the resistor assembly entirely. The reason why none off the other speeds will work is that the resistor or the circuit for the speed four setting has burned out. The lower the setting the more resistance you need to drop the voltage to the blower. The first speed setting requires all four resistors to drop the voltage enough to turn the blower at its slowest speed. Speed 2 needs to turn the blower a little faster so it uses three resistors. Speed 3 uses two resistors and speed 4 uses one.

In some cases the fan will work on high and speed setting 4. The likely cause for this is the speed 3 resistor or circuit has burned out. Speed 4 still works because it doesn't use the lower speeds resistors to control the speed of the blower. If the speed 2 resistor burns out than speed 1 and 2 will not work but 3, 4 and high will continue to work. If the speed 1 resistor burns out than speeds 2, 3, 4, and high will continue to work.

This leads us to how do we know if its the resistor or the switch or the blower. If the blower works on high than we know the blower works. That leaves us with either the switch or the resistor assembly (there are many other possibilities) wich can be easily tested with a test light (or a voltmeter if you choose) The first thing to do is locate the resistor assemble. They can be behind the glove box, under the dash close to the blower motor or under the hood, again usually close to the blower motor. It will typically have 5 to six wires going to it. We'll start by unplugging the connector, turning the key on and connecting your test light to ground.

1.Turn the switch to high and backprope all the wires. Two of them should illuminate the test light. In the diagram below this would be wire E & F. If you don't have a digram then hold the test light on one of the two wires and move the switch to another speed setting. the wire that continuously illuminates the test light regardless of the switch position will be the constant power for high blower speed and will not need to be rechecked in the following steps.

2. Turn the switch to the next lowest setting. Backprobe the remaining wires to see if one of them illuminates the test light. Repeat until you have checked all of the speed settings.

3. If the test light has illuminated a different wire for each setting then we can reasonably assume that the switch is functioning as intended and the source of the problem is the blower resistor.

4. If you find one or more settings (but not all the settings) on the switch that does not illuminate the test light on any wire than we can reasonably assume that the switch has failed.

There are a few other things that can cause blower motors not to work as intended. The switch or the resistor assembly are the two most common problems.

[Hookmaster]

This was from a thread earlier this year when it happened on my 2004 Silverado.

The blower resistor board was the fix. The part # for my 2004 Silverado Crew Cab was 89019088. This was for a bench seat, not the floor console model. It's best to have the VIN# to make sure you get the right part. It was held on by two hex nut screws. It should have taken 30 minutes but it took me 1 hour since the screw above the hump for the shroud was a little tricky to put back in. I now have air movement on setting #1 which I didn't have before. I also noticed that on long freeway trips I needed to put the fan on #3 instead of #2 last fall. So it gave some indication it was failing before it went belly up. The part cost $53.99 with the tax so I probably saved $50-$100 in labor.

The blower resistor board is located in the duct but it is under the dash board. Take off the shroud and it is easy to replace. When putting the shroud back on, getting the hex-head screw above the hump back in was tricy. This is what took the most time for me. You need a deep socket in a small size.

[Jaspernuts]

Make sure the wiring harness is not melted. I have seen this a lot with this model.