This tutorial will help you test the blower motor resistor block on the 1995, 1996, and 1997 Ford Ranger (1995-1997 Mazda B3000).
Testing the blower motor resistor basically involves testing the continuity of the resistor block.
The tests are very easy and are done with a multimeter. All is explained in a step-by-step way.
You'll be able to find out if the blower motor resistor is bad or not.
Contents of this tutorial:
NOTE: If you need to test the blower motor, see this tutorial: How To Test The Blower Motor (1995-1997 3.0L Ford Ranger).
You can find the blower motor system circuit diagram here: Blower Motor Circuit Diagram (1995-1997 3.0L Ford Ranger).
Blower Motor Resistor Basics
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
We're gonna' test the continuity of the metallic coils of the blower motor resistor.
If blower motor resistor is bad, on your Ford Ranger or Mazda B3000, then one of the coils will show a no-continuity test result.
This continuity test is done with a multimeter in Ohms mode.
In the next page, you'll see the specific resistance values I got testing a good working blower motor resistor or you can click here: Blower Resistor Continuity Specification Tables.
NOTE: I suggest you use a digital multimeter for your continuity tests, although an analog multimeter will work just fine. If you need to buy a multimeter, take a look at 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 take a look at what your test results mean:
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.