This tutorial will help you test the blower motor on the 2002-2006 Nissan Sentra.
The blower motor is a very easy component to test and in this tutorial I'll explain how to do it in a step-by-step way.
Contents of this tutorial at a glance:
You can find this tutorial in Spanish here: Cómo Probar El Motor Del Soplador (2002-2006 2.5L Nissan Sentra) (at: autotecnico-online.com).
NOTE: You can find the 2002-2006 2.5L Nissan Sentra blower motor circuit diagram here: Blower Motor Circuit Diagram (2002-2006 2.5L Nissan Sentra).
Blower Motor Basics
Sooner or later, the blower motor on your Nissan Sentra will fail. And when it does, it'll fail in one of two ways:
- The blower motor will stop working completely.
- The blower motor will run, but run with a lot of bearing noise.
A blower motor with worn out bearings will use an extreme amount of current (from the mechanical resistance to the motor rotation). This high amperage draw can overheat and destroy the blower motor resistor.
TEST 1: Testing The Amperage Draw Of The Blower Motor
The very first thing that we're gonna' do is test the amperage draw of the blower motor.
What we want to do is make sure that the blower motor is using less than 30 amps (when its running).
The cool thing is that we can do this without using an ammeter since this test can be done with a simple multimeter.
To be bit a more specific, the amperage draw test simply involves testing the resistance of the blower motor and then using Ohm's Law to calculate it's amperage draw (Ohms Law: Amps=Volts ÷ Ohms).
NOTE: If you don't have a multimeter and need to buy one, check out my recommendations here: Buying A Digital Multimeter For Automotive Diagnostic Testing.
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 connector and not the vehicle's wiring harness connector.
Divide 12.5 by the resistance value you got in step 3 (12.5 is the battery voltage value). 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 0.4 Ohms. This is what the math would look like: 12.5 ÷ 0.4 = 31.25 and this would translate to 31.25 Amps.
Let's take a look at your test results:
CASE 1: Your test result resulted in a calculation of under 30 Amps. 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: Your test result resulted in a calculation of 30 Amps or more. This test result tells you that the blower motor, on your Nissan Sentra, is defective and needs to be replaced.