Testing the blower motor, on the 1997-1999 Dodge Dakota and 1998-1999 Durango, involves two simple tests.
One is an amperage draw test done with a multimeter. The other involves manually adding power and Ground to it to see if it runs or not.
In this tutorial, I'll explain both in a step-by-step way.
Contents of this tutorial:
You can find this tutorial in Spanish here: Cómo Probar El Motor Del Soplador (1997-1999 Dodge Dakota Y Durango) (at: autotecnico-online.com).
NOTE: You can find the blower motor resistor block test here: How To Test The Blower Motor Resistor (1997-1999 Dodge Dakota And Durango).
Blower Motor Basics
In a nutshell, the blower motor gets power on one wire and Ground on the other. When both of these are present, the blower motor runs.
Of course, it's a little more complicated than that, but for our testing purposes this will suffice.
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.
The 'a lot noise' I'm talking about is the growling noise that's caused by worn out blower motor bearings.
TEST 1: Testing The Amperage Draw Of The Blower Motor
You may asking yourself: 'Why test the amperage draw of the blower motor?'.
It's because many times the blower motor, although defective, continues to run. And when this happens, the current the blower motor is pulling will fry the blower resistor and/or the blower motor switch and/or the blower motor fuse.
Since this is a simple multimeter resistance test, it's best to get it out of the way right away.
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 amperage draw, of your Dakota or Durango's blower motor should be under 40 amps.
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 40 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 40 Amps or more. This test result tells you that the blower motor, on your 1997-1999 Dodge Dakota, is defective and needs to be replaced.