Replacing a blower resistor on a Dodge Dakota.
Electrical Repairs:

Replacing And Re-Wiring The Heater Blower Resistor On A 1993 Dodge Dakota

Fan Doesn't Work On Every Speed...

 

In This Article:

The blower motor resistor is removed and replaced. The damaged electrical connector is cut off and spade connectors are installed on the ends of the wires.

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Skill Level: 2 (Basic) Time Taken: About 30 Minutes

By Bruce W. Maki, Editor

Start:

I have two Dodge Dakota's, and on both of these trucks the AC/heater blower has stopped working on certain speeds.

If the blower doesn't work at all, the first thing to check is the fuse, which is in the fuse box under the hood, on the driver's side. The blower uses a 50 Amp fuse.

But when the blower works on one or more of the four speeds, the problem is something besides the fuse. When I first had this problem, I thought the fan speed switch on the dashboard was faulty... but I was wrong. The problem was actually in the resistor network that reduces the voltage to the blower at lower speed settings. On my 1996 Dakota, I replaced the resistor block a couple of years ago, and then about 6 months ago a couple of fan speeds stopped working. It turned out the problem was in the wires that connect to the resistor.

Recently the fan on my 1993 Dakota stopped working on all speeds except High. I knew exactly what the problem was.

1993 Dodge Dakota:

The location of the blower resistor: In the engine compartment, high up on the firewall, near the passenger side.

Location of heater blower resistor, 1993 Dodge Dakota.

 

AC/heater blower resistor, Dodge Dakota. A closer view: There is a 5-wire connector that plugs into the back of the resistor network.

 

Just like my other Dakota, the plastic connector had melted. Even the insulation on some of the wires had melted. Corroded and melted resistor connector, Dodge.

 

Corroded resistor terminals, Dodge truck. When I pulled off the electrical connector, some of the lugs on the resistor fell apart. I suspect this was caused by plain-old corrosion.

 

The bottom of the connector was worse than the top. Look at that "prong" of plastic that melted away (top center of photos), exposing one of the spade connectors.

Memo to Chrysler: What the hell are you doing? Why didn't you issue a recall to fix this problem before it catches someone's truck on fire?

Melted electrical connector for heater blower resistor, Dodge.

 

Removing screws for blower resistor from firewall, Dodge Dakota.

I removed the screws with a 5/16" socket.

They were very rusty.

 

I pulled the resistor network out of the hole in the firewall.

There is a foam gasket behind the base plate.

Removing resistor, Dodge.

 

Electrical connector for heater/AC fan resistor, Dodge truck.

I cut each wire about an inch away from the electrical connector.

Then I realized that there are TWO wires that are black with a tan stripe, the High fan speed position wire (C7, which goes to the fan switch) and the blower motor wire (H6).

After looking at the circuit diagram in my shop manual, I identified all the wires. Here I've noted the wire numbers that are indicated in the service manual.

Note that electrical current flows through the Blower wire (H6) in ALL fan speeds. If this wire (or its connection) is faulty, then the fan won't work at all, even though the fuse is good.

 

Getting Wires Mixed Up:

For a moment I wasn't sure about the locations of the two black/tan wires. The electrical schematic in the service manual shows black/tan wire H6 coming from the blower motor. The other wire of the blower motor leads to the fuse block (fuse 1, 50 Amps). When the dashboard switch is set to High, the blower wire H6 is grounded through the resistor and then the switch, and the circuit is completed. Simple.

To prove which black/tan wire went to the blower, I just used a heavy-gauge jumper wire to connect between one of the black/tan wires and a ground location on the firewall. When I touched the ground point, there were some sparks and I could hear the blower running. That's the blower wire H6.

To perform this test I had to have the ignition turned to ON (but without the engine running), so there was power applied to the blower.

I'll note that my newer (1996) Dakota has a gray wire for the C7 wire that runs to the High setting on the fan speed switch. I guess that the engineers at Chrysler saw the folly in using two wires of the same gauge and color coding.

 

This is the new resistor network that I bought at a local auto parts store for less than $7.

The first time I replaced a resistor, my usual parts store didn't carry it, so I bought a new resistor from my local Dodge dealer. It cost a lot more than seven bucks.

This part is made by Standard Motor Products, the part number is RU95.

New blower resistor, Standard Motor Products RU95, for Dodge truck.

 

Electrical connectors on blower resistor, Standard RU95.

There are 5 spade connectors.

I marked the lug that connects to the blower motor, which is wire H6.

 

The gasket has an adhesive backing. I peeled of the release paper and applied the gasket around the opening in the firewall. Installing foam gasket for blower motor resistor, Dodge.

 

Tightening screws on blower resistor. I installed the new blower motor resistor network in the firewall.

 

Using a pair of wire strippers, I removed about 1/4" of insulation from the end of each wire. Stipping ends of wires.

 

Crimping new spade terminal connector.

I attached yellow spade connectors to the 2 heaviest wires, which are both 12 gauge.

 

Yellow connectors are for 10 to 12 gauge wire.

This type of connector just pushes onto the metal tabs on the resistor. The fit should be snug.

New spade terminal connector.

 

Smaller wires with new spade connectors.

Then I installed blue spade connectors on the other wires, which are 14 and 16 gauge. (It didn't show up well in this photo, but the plastic on those spade connectors is actually light blue.)

Blue connectors are for 14 to 16 gauge wire.

 

I connected each wire to the resistor block, using the cut-off plastic connector as a guide to wire placement.

NOTE: Some later vehicles (such as my 96 Dakota) may use a gray #12 wire for that top-right connection, which is the High fan speed wire C7.

Re-wired fan motor resistor on Dodge Dakota, 1993.

 

Dielectric terminal grease for electrical connections.

Extra Help:

Before connecting the wires, I applied a dab of dielectric grease to each spade connector.

This should help slow down the corrosion process. Whenever possible I like to use dielectric grease on electrical connections that are exposed to the weather. For example, I often apply this stuff to trailer wiring connectors.

When the repair was complete, I wrapped a couple of zip ties around the wires to hold them together.

 

My Other Dakota:

Re-wired resitor on my 1996 Dakota.

I replaced the resistor about 3 years ago, but I repaired the connections about 6 months ago because the fan stopped working on certain speeds.

Note that this resistor is rotated 180 degrees from my older truck. I'm guessing that it was built this way (not that it matters).

Alternate resistor orientation in 1996 Dodge Dakota.

 

Blower motor resistor without connector, wires labelled.

View from other side.

I had written the wire colors on the firewall, so they won't get mixed up if I should need to unplug them someday.

 

AC / Heater Blower Motor Fuse Location:

The blower motor is powered by a 50 Amp fuse (red arrow).

This fuse block is in the engine compartment, adjacent to the driver's side fender.

Location of 50 Amp fuse for blower motor, Dodge truck.

 

More Info:

Tools Used:

  • 5/15" Socket
  • Ratchet
  • Wire Stripper / Crimper Tool

Materials Used:

  • Blower Motor Resistor, Standard Motor Products Part# RU95, (About $7)
  • Spade Connectors, 2 Yellow, 3 Blue
  • Dielectric Terminal Grease

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Written April 25, 2009