The blower motor, on your Chevy S10 (GMC S15), is one of the easiest components to test. In this tutorial I'll show you how in a step-by-step manner.
Here are the contents of this tutorial at a quick glance:
- Symptoms A Of Bad Blower Motor.
- TEST 1: Applying Power To The Blower Motor.
- Where To Buy The Blower Motor And Save.
- More GM 2.8L Diagnostic Tutorials.
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.
Puedes encontrar este tutorial en Español aquí: Verificando el Motor del Soplador del A/C (2.8L Chevy S10/ GMC S15) (en: autotecnico-online.com).
Symptoms Of A Bad Blower Motor
The blower motor is located in the engine compartment and if you've already found it, you'll notice it has only one connector. The wire that connects to the blower motor's only male spade connector is a PPL (purple) wire and it feeds the motor with power.
In case you're wondering, ground is provided by a ground strap that connects to the blower motor's metal case. Since the blower motor and it's circuits are in plain view, you and I can easily test it to find out if it's good or bad.
Now, when the blower motor fails, you'll see:
- Blower motor doesn't work (at any speed you put the blower switch on).
- The blower motor speed is slow (even when on HI speed).
- The blower motor makes a lot of noise.
The focus of this tutorial diagnosing a ‘no blower’ condition.
TEST 1: Applying Power To The Blower Motor
We don't have to remove the blower motor to test it and the test steps below assume you're testing it in place.
The PPL wire is the one that feeds power to the blower motor and the other wire (BLK) grounds the blower motor case. This ground is important since without it, the blower motor won't run.
As a safety precaution you should use a fused jumper wire or a power probe to apply 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 insert a 30 amp fuse into it.
NOTE: If you've already removed the blower motor and want/need to bench test it, you'll have to ground the blower motor's metal case or the test won't work. Grounding the case is important due to the fact that the blower motor gets ground through it case.
Alright, these are the test steps:
Disconnect the blower control motor from its PPL wire electrical connector.
NOTE: Leave the BLK wire connector connected to the blower motor's case so that the blower motor can continue to get ground.
Connect a fused jumper wire to the blower motor male spade terminal that connects to the PPL wire of the connector.
The blower motor should run as you soon as you connect the other end of this fused jumper to your vehicle's car battery positive terminal.
NOTE: If you're testing the blower motor while it's still bolted in place, you don't have to ground it with a separate ground jumper wire.
Let's take a look at what your test results mean:
CASE 1: The blower motor ran without any grinding noise when you applied battery power with the jumper wire. This is the correct and expected test result and tells you that the blower motor is good.
CASE 2: The blower motor ran and made a loud grinding noise when you applied battery power with the jumper wire. This tells you that the blower motor has an internal problem (usually bad brushes or bearings).
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 run when you applied battery power with the jumper wire. 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.