In this tutorial you'll learn how to test the blower resistor on the 1995, 1996, and 1997 2.3L Ford Ranger (Mazda B2300).
Testing the blower resistor block is a breeze and all you'll need is a multimeter.
In case you need it, to further help you diagnose a blower resistor problem, you can find the blower system wiring diagram here: Blower Motor Circuit Diagram (1995-1997 2.3L Ford Ranger).
Contents of this tutorial at a glance:
You can find this tutorial in Spanish here: Cómo Probar La Resistencia Del Soplador (1995-1997 2.3L Ford Ranger) (at: autotecnico-online.com).
NOTE: If you need to test the blower motor, see this tutorial: Testing The Blower Motor (1995-1997 2.3L Ford Ranger).
Blower Motor Resistor Basics
The current that passes thru' the blower motor is routed thru' the resistors that make up the resistor block to reduce its speed.
The more resistors the current has to pass thru', the slower the blower motor speed.
In reducing the blower motor fan speed, the blower resistor gets very hot. Eventually, it's this heat that's gonna' fry it.
To help keep it cool, the blower resistor block is located in the blower motor's air stream. Still, it's gonna' eventually fail.
When the blower motor resistor block fails, you'll usually see one of the following symptoms:
- Blower motor works in high-speed only.
- Blower motor works in some speeds, but NOT all speeds.
It's common for the resistor connector terminals to corrode or for the connector to burn and melt. This will make disconnecting the connector from the blower motor resistor block very difficult.
Another common problem is finding the resistor block coils corroded or burned out when removing the resistor block for testing.
TEST 1: Resistance Testing The Blower Motor Resistor
To get our blower resistor diagnostic going, we're gonna' remove it from its place (in the engine compartment) and test its continuity with a multimeter in Ohms mode.
You'll know the blower motor resistor is defective because: 1.) One of the resistance coils will show a no-continuity test result or 2.) You'll be able to visually see that one or several resistance coils are burned off.
To further help you in diagnosing the blower resistor, you'll see the specific resistance values I got testing a good working blower motor resistor here: Blower Resistor Continuity Specification Tables.
NOTE: Don't have a multimeter and need to buy one? Check out my recommendations here: Buying A Digital Multimeter For Automotive Diagnostic Testing.
Alright, these are the test steps:
Disconnect the blower motor resistor from its connector and remove it from its location.
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.
Place your multimeter in Ohms mode.
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 analyze your blower resistor continuity test results:
CASE 1: Continuity exists between all the blower motor resistor terminals. This is the correct and expected test result.
If there isn't any burn damage to the resistor's coils or its connector, then you can conclude the blower motor resistor block is OK and not defective.
CASE 2: Continuity DOES NOT exist between some of the blower motor resistor terminals. This test result tells you that your Ford Ranger's blower motor resistor is defective and needs to be replaced.
If the resistor block's connector is damaged or is melted, it must be replaced with a new one.