How To Test The Blower Motor Resistor Block (1998, 1999, 2000, 2.5L Ford Ranger And Mazda B2500)

This tutorial will help you to diagnose the blower motor resistor block on the 1998, 1999, 2000, and 2001 2.5L Ford Ranger and Mazda B2500 pickup truck.

The blower motor resistor is a pretty simple component to test, and in this tutorial I'll explain how to do it in a step-by-step that way. You will be able to find out if the blower motor resistor is defective or not.

The following tutorials may come in handy:

  1. How To Test The Blower Motor Switch (1998-2000 2.5L Ford Ranger).
  2. How To Test The Blower Motor (1998-2001 2.5L Ford Ranger).

NOTE: You can find the blower motor circuit diagram here: Blower Motor Circuit Diagram (1998-2000 2.5L Ford Ranger).

Blower Motor Resistor Basics

The blower motor resistor is the component tasked with reducing the amount of current that passes through the blower motor. This reduction in current is what lowers the blower motor speed.

In case you're wondering, the blower motor resistor accomplishes this reduction in current by converting some of the current into heat.

This causes the blower motor to run at some pretty extreme temperatures and it's these high operating temperatures that will eventually destroy it.

What helps the blower motor cool down (and last longer) is its location in the blower motor's air output stream.

Symptoms Of A Defective Blower Motor Resistor

When the blower motor resistor fails, you'll usually see one of two things. These are:

  1. The blower motor only works on high speed.
  2. The blower motor works on some but not on all of its speeds.

Cool thing is that testing the blower resistor block is a pretty simple thing to do and in the next section we'll get testing.

TEST 1: Testing The Continuity Of The Blower Motor Resistor

Resistance Testing The Blower Motor Resistor. How To Test The Blower Motor Resistor (1998, 1999, 2000 2.5L Ford Ranger And Mazda B2500)

The blower motor resistor is located in the engine compartment of your 2.5 ford Ranger (Mazda B2500).

To be a bit more specific, it's located next to the blower motor on the passenger side of the engine compartment's firewall.

To test the continuity of the resistor block, you'll need to remove it from its place.

The blower motor resistor block continuity test is done with a multimeter in ohms mode.

These are the test steps:

  1. 1

    Disconnect the blower motor resistor from its connector and remove it from its location.

  2. 2

    Visually inspect the blower motor resistor block and connector for burn damage and severe corrosion.

    If the blower resistor block and connector have any heat damage (in other words: burns or are melted), you can stop here and conclude they're bad and need to be replaced.

  3. 3

    Place your multimeter in Ohms mode.

  4. 4

    Check for continuity across two terminals at a time. Continuity should be present between all terminals.

    NOTE: If continuity DOES NOT exist between 2 terminals, your multimeter will display the letters OL (Open Loop).

Let's examine your test result:

CASE 1: Continuity is present between all terminals. This is the correct and expected test result. With this test results You can conclude that the resistor block, of your 2.5L Ford Ranger (Mazda B2500), is functioning correctly.

CASE 2: Continuity is present between 2 terminals. This test result lets you know that the resistor block is defective and needs to be replaced with a new one.