One of the things that makes testing the blower resistor assembly a breeze, on the 1991-1996 3.9L Dodge Dakota, is the fact that it's so easy to get to.
The test itself is done with a multimeter and is very easy to do. In this tutorial, you'll find it explained in detail. With your test results you'll be able to conclude if it's bad or not.
I'm also gonna' show you where you can buy the blower motor resistor and save a few bucks.
Contents of this tutorial at a glance:
You can find this tutorial in Spanish here: Cómo Probar El Conjunto De Resistencias Del Motor Soplador (1991-1996 3.9L V6 Dodge Dakota) (at: autotecnico-online.com).
APPLIES TO: This tutorial and the blower motor resistor in the images I'm using in this tutorial applies to: 1991, 1992, 1993, 1994, 1995, 1996 3.9L V6 Dodge Dakota.
WIRING DIAGRAM: You can find the blower motor circuit diagram, for the 1991-1995 3.9L Dodge Dakota, here: Blower Motor Circuit Diagram (1991-1995 3.9L Dodge Dakota).
Blower Motor Resistor Basics
The blower motor resistor assembly, on your 3.9L Dodge Dakota, is tasked with reducing the current that the blower motor uses. The less current the blower motor uses, the slower it runs.
What makes this reduction in current (and speed possible) is the three resistor coils that make up the blower resistor assembly.
In a nutshell, as current passes through the resistor coils, the current is reduced.
To be a bit more specific:
- When the current is reduced by three resistors, the blower motor runs in LO speed.
- When the current is reduced by two resistors, the blower motor runs in Medium 1 (M1) speed.
- When the current is reduced by one resistor, the blower motor runs in Medium 2 (M2) speed.
- When the current is NOT reduced by any of the resistors, the blower motor runs in HI speed.
The reduction in current is the consequence of the resistor's ability to convert some of the current flowing thru' them into heat. Unfortunately it's this process (of converting current into heat) that eventually will destroy the blower motor resistor assembly.
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 very 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.
Where To Buy The Blower Motor Resistor
The blower motor resistor assembly is not an expensive part. Still, the following links will help you to comparison shop and save you a few bucks on the blower resistor assembly and its connector:
NOTE: The blower motor resistor in the links above will fit the following vehicles:
- 1991, 1992, 1993, 1994, 1995, and 1996 3.9L V6 Dodge Dakota.
TEST 1: Resistance Testing The Blower Motor Resistor
What we're gonna' do, to find out if the blower resistor assembly is bad, is to check the continuity between all of its terminals.
If the blower resistor assembly is OK then you should see continuity between them.
If the blower motor resistor assembly is bad, then you're gonna' have no-continuity between 2 of its terminals.
Testing continuity between the terminals simply involves testing the resistance between them with a multimeter in Ohms mode.
NOTE: To see actual resistance specifications for the continuity test of this test section, go here: Blower Resistor Continuity Specification Tables.
NOTE: If you don't have a multimeter or need to upgrade yours, take a look at my recommendations here: Buying A Digital Multimeter For Automotive Diagnostic Testing.
OK, let's get started:
- 1
Disconnect the blower motor resistor from its connector and remove it from its location.
- 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. See: Example Of Damaged Blower Resistor Assembly Connector. - 3
Place your multimeter in Ohms mode.
- 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 take a look at what your test results mean:
CASE 1: Continuity exists between all the blower motor resistor terminals. This is the correct test result and confirms that the blower motor resistor assembly is OK.
CASE 2: Continuity DOES NOT exist between some of the blower motor resistor terminals. This test result tells you that the blower motor resistor assembly is bad and needs to be replaced.
You can find my recommendations, on where to buy the blower motor resistor assembly, here: Where To Buy The Blower Motor Resistor.
