The blower motor, on your 2.8 V6 Chevy S10 pickup (GMC S15 pickup, GMC Sonoma), is one of the easiest components to test.
In this tutorial, I'll show you how to test it in a step-by-step manner. With your test results, you'll quickly determine if the blower motor is good or bad.
Contents of this tutorial:
The following tutorials (on testing the blower resistor assembly and blower switch) compliment this one on testing the blower motor:
- How To Test The Blower Resistor (2.8L Chevy S10/GMC S15).
- How To Test The Blower Control Switch (2.8L Chevy S10/ GMC S15).
- 1991-1993 2.8L Chevy S10 Blower Motor Circuit Diagram.
This tutorial also applies to the 2.8L Chevy S10 Blazer, 2.8L GMC S15 Jimmy. See the 'Applies To' box on the left column (desktop) or at the bottom of the page (mobile device) for more info.
You can find this tutorial in Spanish here: Verificando el Motor del Soplador del A/C (2.8L Chevy S10/ GMC S15) (at: autotecnico-online.com).
APPLIES TO: This tutorial applies to the following vehicles:
- 2.8L Chevrolet S10 Pickup: 1988, 1989, 1990, 1991, 1992, 1993.
- 2.8L GMC S15 Pickup: 1988, 1989, 1990.
- 2.8L GMC Sonoma: 1991, 1992, 1993.
Symptoms Of A Bad Blower Motor
The blower motor is located in the engine compartment and if you've already located it, you'll notice that it only has one connector.
The wire that connects to the blower motor's single spade connector is a purple (PPL) wire and provides power to the motor.
The blower motor gets Ground via a ground strap connected to its metal case.
When the blower motor fails, you'll see one or more of the following symptoms:
- Blower motor doesn't work (at any speed you put the blower speed switch on).
- The blower motor speed is slow (even when on HI speed).
- The blower motor makes a lot of noise.
- Blower motor fuse blows when turning on the AC-heater system.
Because the blower motor and its circuitry (wires) are in plain view, you and I can easily test it to see if it's good or bad.
TEST 1: Testing The Amperage Draw Of The Blower Motor
The first thing we need to do to determine if the blower motor is good or bad is to find out its current draw (usage).
When the blower motor is new, it draws a minimal amount of current (amps), but as it wears out, its current draw increases.
Eventually the blower motor will require so much current, more than the system can supply, that it will not run or will run but blow the blower motor fuse.
Twenty-five amps is the maximum current that the blower motor can use. If the current is greater than 25A, you can conclude that the blower motor is defective and needs to be replaced.
To determine the current draw of the blower motor, we'll run a simple multimeter resistance test and with the resistance value obtained, we'll use Ohm's Law to determine its current draw (usage).
These are the test steps:
- 1
Disconnect the blower motor from its 1-wire connector.
- 2
Place your multimeter in Ohms mode.
- 3
Connect the red multimeter test lead to the blower motor male spade terminal of the 1-wire connector.
- 4
Connect the black multimeter test lead to a clean rust-free and unpainted surface on the blower motor body.
- 5
Take note of the resistance value your multimeter reports.
- 6
Divide 12.5 by the resistance value you got in the previous step.
Let's say that you got a resistance reading of 0.4 Ohms in step 5. You would then do the following calculation: 12.5 ÷ 0.4 = 31.25. Which tells you that the blower motor has an amperage draw of 31.25 Amps.
Let's examine your test results:
CASE 1: Your test result shows the blower motor is using less than 25 amps. This is the correct and expected test result. With this test result You can conclude that the current draw of the blower motor is within specification.
The next test is to manually apply battery power and Ground to the blower motor. Go to: TEST 2: Applying 12 Volts To The Blower Motor.
CASE 2: Your test results shows that the blower motor is using 40 or more amps. This test result lets you know that the blower motor is defective and needs to be replaced.
TEST 2: Applying 12 Volts To The Blower Motor
NOTE: You don't have to remove the blower motor to test it and the test steps below assume you're testing it in place.
The purple (PPL) wire provides power to the blower motor and the black (BLK) wire provides Ground to the blower motor housing. This Ground is important, otherwise the blower motor will not run.
As a safety precaution, use a fused jumper wire or a Power Probe to provide battery power to the blower motor.
You can make your own fused jumper wire by using an inline fuse holder that you can buy at your local auto parts store and inserting a 30A fuse (see the illustration above).
NOTE: If you have already removed the blower motor and want/need to test bench test it, you must Ground the metal housing of the blower motor, otherwise the test will not work. Grounding its metal housing is important because the fan motor is Grounded through its case.
Alright, these are the test steps:
- 1
Disconnect the purple wire from the blower motor.
NOTE: Leave the black wire connector connected to the blower motor's case so the blower motor gets Ground. - 2
Connect one end of your fused jumper wire to the battery positive (+) post.
- 3
Connect the other end of the fused jumper wire to the blower motor male spade terminal that connects to the PPL wire of the connector.
- 4
The blower motor should run without a metal to metal grinding sound.
Let's take a look at what your test results mean:
CASE 1: The blower motor ran without any grinding noise. This is the correct and expected test result.
You can conclude that the blower motor is good and does not need replacement if you have also confirmed that its amperage draw is below 25A.
CASE 2: The blower motor ran and made a loud grinding noise. This tells you that the blower motor has an internal problem (usually bad brushes or bearings).
Bad bearings or bushings will cause the blower motor to use more current (amperage) to run.
Depending on how bad the blower noise is, it would be a good idea to replace it with a new one.
CASE 3: The blower motor DID NOT. This test result tells you that the blower motor is bad and needs to be replaced.
The next subheading will show you where you can buy the blower motor and save a few bucks.
Where To Buy The Blower Motor And Save
You can find the blower motor in any auto parts store. If you're wanting the buy the original AC Delco blower motor, you can buy it online for a whole lot cheaper than somewhere local.
The following links will help you comparison shop for the AC Delco and after market blower motors:
Will the above blower motor fit your particular S10/S15 pickup? Don't worry, once you get to the site they'll make sure it fits (by asking you the specifics of your particular vehicle). If it doesn't fit, they'll find you the right one.
More 2.8L Chevy S10 Pickup, GMC S15 Pickup, And GMC Sonoma Tutorials
You can find a complete list of tutorials for the 2.8L V6 Chevrolet S10 pickup, GMC S15 pickup, and GMC Sonoma in this index:
Here's a sample of the articles, you'll find in the Index of Articles:
- How To Test The Fuel Pump (1988-1993 2.8L Chevrolet S10 Pickup, GMC S15 Pickup, GMC Sonoma).
- How To Test Engine Compression (1988-1993 2.8L Chevrolet S10 Pickup, GMC S15 Pickup, GMC Sonoma).
- How To Test The EGR Valve (1988-1993 2.8L Chevrolet S10 Pickup, GMC S15 Pickup, GMC Sonoma).
- How To Test The Starter Motor (1988-1993 2.8L V6 Chevrolet S10 Pickup, GMC S15 Pickup).
If this info saved the day, buy me a beer!
