Testing the blower motor on your 2.2L Chevrolet S10 (GMC Sonoma) is a pretty easy affair.
The cool thing is that testing the blower motor involves two simple tests and in this tutorial I'll explain how to do it in a step-by-step way.
NOTE: This tutorial applies to the 1994-2003 Chevy S10 and GMC Sonoma's equipped with a 2.2L 4 cylinder and 4.3L V6 engines.
Contents of this tutorial at a glance:
- Blower Motor Basics.
- TEST 1: Testing The Amperage Draw Of The Blower Motor.
- TEST 2: Applying Power And Ground To The Blower Motor.
- Where To Buy The Blower Motor.
- More 2.2L GM Tutorials.
NOTE: You can find the blower motor resistor test here: How To Test The Blower Motor Resistor (1995-2003 2.2L Chevy S10).
Blower Motor Basics
The blower motor, on your Chevy S10 (GMC Sonoma) is a simple component to test. You'll notice that the connector, on the blower motor itself, has 2 male spade terminals and that it's engine wiring harness connector has 2 female terminals.
In a nutshell, one wire is a power (battery voltage) wire and the other wire provides ground. To be a bit more specific, the power wire is the purple (PPL) wire and the ground wire is the black (BLK) wire.
When the blower motor fails (or starts to fail), it will do one of 2 things:
- Stop working completely.
- Run, but run with a lot of noise.
TEST 1: Testing The Amperage Draw Of The Blower Motor
The first test I'm gonna' suggest is an amperage draw test of your S10's blower motor.
This is a very simple test that requires reading the blower motor's internal resistance with a multimeter in Ohms mode.
Once we have the blower motor's resistance value, we'll use Ohm's Law to calculate it's amperage draw (Ohms Law: Amps=Volts ÷ Ohms).
The purpose of this test is to make sure that the blower motor, on your S10 (or Sonoma) is drawing well below the amperage rating of its fuse (25 or 30 Amps) when it's operating.
Why find out the blower motor's amperage draw? Because in some cases, even though the blower motor runs, it's drawing too much amperage that it'll eventually blow out the HVAC fuse, burn out the blower motor resistor block, and/or the blower motor switch.
So, if the blower motor's amperage draw is above the amperage rating of its fuse, then it' s defective and needs to be replaced.
IMPORTANT: The maximum amperage draw on the 1994-1995 S10 (Sonoma) is 25 Amps. The maximum amperage draw on the 1998-2003 S10 (Sonoma) is 30 Amps.
Let's get started:
Disconnect the blower motor from its electrical connector.
Place your multimeter in Ohms mode.
Measure the resistance of the blower motor with your multimeter. You'll be testing across the blower motor's two male spade terminals.
Divide your resistance value by 12.5. The result of this calculation is the amount of amperage the fan motor is using.
To be a little more specific: Let's say that the resistance reading was .4 Ohms. This is what the math would look like: 12.5 ÷ .4 = 31.25 and this would translate to 31.25 Amps.
The blower motor's amperage draw should be below: 1994-1997: 25 Amps, 1998-2003: 30 Amps.
Let's take a look at your amperage draw test results:
CASE 1: The amperage draw of the blower motor is below the Amps specified. This is the correct and expected test result and let's you know that the blower motor amperage draw is within specification.
The next step is to manually apply power and ground to the blower motor itself. For this test go to: TEST 2: Applying Power And Ground To The Blower Motor.
CASE 2: The amperage draw of the blower motor is above the Amps specified. This test result tells you that the blower motor, on your Chevy S10 (GMC Sonoma), is defective and needs to be replaced.