Testing the blower motor on the 1992, 1993, and 1994 3.0L V6 Ford Ranger isn't hard.
In this tutorial I'll show you how to do it in a step-by-step way. The two tests in this tutorial will help you find out if it's defective or not.
Contents of this tutorial at a quick glance:
If you need to test the blower resistor, this tutorial will help: How To Test The Blower Motor Resistor (1992-1994 3.0L Ranger).
NOTE: You can find the blower motor circuit diagram here: 1992-1994 3.0L Ranger Blower Motor Circuit Diagram.
Puedes encontrar este tutorial en Español aquí: Cómo Probar El Motor Del Soplador (1992-1994 3.0L Ford Ranger) (en: autotecnico-online.com).
Blower Motor Basics
Sooner or later, the blower motor's bearings or brushes will wear out and it will malfunction 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.
When the blower motor's bearings to wear out, it 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 and blower switch.
The cool thing is that you and I can check the blower motor's amperage draw without an expensive ammeter. TEST 1 will explain how to check it with a multimeter in Ohms mode (and using Ohms law).
TEST 1: Testing The Amperage Draw Of The Blower Motor
The very first thing we want to do is find out if your 3.0L Ford Ranger's blower motor's amperage draw is more than 30 Amps, because if it is, then you can conclude that it's bad (and needs to be replaced).
To get the amperage draw, we'll read the blower motor's internal resistance and then use Ohms law to figure out its current usage (Ohms Law: Amps=Volts ÷ Ohms).
This is a very easy and simple test that will give you a very accurate test result. But you may have to remove the blower motor to access the blower's terminals with your multimeter.
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: The blower motor's amperage draw is below 30 Amps. This is the correct and expected test result.
The next step is to make sure it runs. Go to: TEST 2: Applying Power And Ground To The Blower Motor.
CASE 2: The blower motor's amperage draw is 30 Amps or more. This test result tells you that your 3.0L Ford Ranger's blower motor is defective and needs to be replaced.