How to Test a Chevy Suburban Blower Motor

How to Test a Chevy Suburban Blower Motor

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The blower motor in your Chevy Suburban is critical to your climate control, and when it starts to fail there’s several symptoms that are easy to spot. When your blower motor starts to fail, your air conditioning or vents will operate at just one speed or not at all. Testing your Chevy blower motor is easy to do using a set of specified procedures, and today I’ll be showing you how to get this done without taking it to a mechanic.

Today’s test vehicle is a 2000 Chevy Suburban and this test does apply to different GMC cars and trucks as well. Because the blower motor is typically just a fan, the component we’ll be testing is the blower motor resistor. This aftermarket part number for this blower motor is 20080, and it’s the same for many Pontiac and Oldsmobile vehicles of the same generation.

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The blower motor resistor in your Chevy is responsible for regulating voltage and changing the speed of your blower fan. This is done through a network if resistors that can kick down the circuit voltage by introducing more resistance to make the blower motor spin slower.

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Over time these resistors build up in heat, causing it to fail. When your resistors begin to burn out, it’s only a matter of time until you lose the lower speeds until only the maximum speed works. If your resistor is beginning to go out, it can cause several symptoms, from screeching or odd noises to your blower motor only working at full blast or at maximum speed.

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There’s four pins in this Chevy Suburban blower motor and you can use them to test the functionality of your resistor. The resistor is located on the backside of your blower motor, and that’s under the passenger side dashboard in your Suburban.

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This tutorial assumes that you are comfortable working around the electronics of your 4.3L, 5.0L, or 5.7L Suburban. To access your blower motor and the resistor, the lower panel of your Suburban dash must be removed.

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Once you have the bolts removed to this lower tray, slide it out and remove to gain full access to your blower motor. The 4 pin connector to your resistor can be seen after you’ve pulled down on the motor. There’s three 5mm bolts that hold the resistor in place, remove them and slide the resistor out of the blower motor assembly.

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Once you have the resistor removed, flip it over to inspect the wiring. Ensure that the wiring is intact and doesn’t have any signs of exposure or corrosion. The four wires are labeled 1-4 in the diagram below, and the pinout of the resistor is listed below.

  • 1 Yellow – LO Input from AC-Heater Panel
  • 2 Blue – Output to Blower Relay
  • 3 Light Brown – Input from AC-Heater Panel
  • 4 Light Blue – M2 Input from AC-Heater Panel

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If your wiring doesn’t quite match the colors specified above, do not worry. Just use our Chevy Suburban blower motor resistor diagram as a guide. Make sure to keep the top locking pin as your guide and go from right to left from PIN 1 to PIN 4.

Begin the testing procedure by using a multimeter, if you aren’t sure what that is, or how to use one check our guide here. To check for voltage you must test the pins at each position at each different vent speed. You can do this by carefully activating your blower motor and turn the vent speed to LO. Af this point you should test PIN 1 for voltage.

How do you test your Suburban resistor motor? Insert your key and turn to the “ON” position, and then turn on your vents by turning the knob to LO. Unplug your resistor harness and test at PIN 1 for 12 volts.

Now turn the knob to the M1 position, you should see voltage at PIN 3. The next speed to check is M2 and the pin that corresponds is PIN 4. If you do not have voltage at these pins, it’s not your blower motor resistor that is the problem. The problem is your air conditioning / heater control panel, so make sure to replace the panel to fix your Suburban vents.

 

If you have 12 volts at all three pin locations, this means you can continue with the testing procedure. The next step requires a jumper wire which you will be using to check the operation of your resistor. Make sure to use a jumper wire that’s thin enough to probe the female connectors and never force the jumper wire into the connector. Doing so can cause a permanently open condition, and prevent your resistor from ever working.

To proceed turn the key to the ON position, and disconnect the harness to your resistor. First we’ll be testing the LO speed operation, by jumping PIN 1 and PIN 2 together. Your blower should be blowing at maximum, because you are bypassing the LO resistor portion.

The next step is to test terminals 2 and 3 by using the jumper wires. This is the circuit that utilizes M1. Again you should see your vents blowing at maximum, and if you dont see this result it means that your resistor is bad and should be replaced.

Have any questions about our How to guide on testing a Chevy Suburban blower motor? Leave us a message below and let us know!

2 COMMENTS

  1. This writeup was awesome and very helpful, it’s amazing that your blower motor guide was so easy to use and understand. Thanks pro street!

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