[HOW-TO][HVAC][Gen III Dakota][Gen I Durango] Blower Resistor Diagnosis/Replacement

[Silver&Blue4x4]

Since this question, or variations of it, comes up quite often I thought I’d write a thorough how-to which can be linked to or (hopefully) found in a search.


SYMPTOM:

Your heating & air conditioner blower motor suddenly stops working, only works on certain speeds, or just seems to not blow as hard as it used to.

Applies to (as far as I know):
2001 – 2007 Durango
2001 – 2004 Dakota


SOLUTION:

99.9% of the time your blower motor resistor block has gone bad. The resistor block is part of the ground path of the blower motor circuit, which in conjunction with the fan speed selector switch controls the speed of the fan by varying the amount of resistors in the electrical path (more resistors = slower speed, fewer resistors = higher speed). This is an easy fix and the new part costs less than $20. If you’re like me and would like to know for sure, read ahead to the “Troubleshooting” section. If you want to play the percentages and just go ahead and change it, skip ahead to the “Removal & Replacement” section.


TROUBLESHOOTING:

In order to troubleshoot the resistor block it will be easiest if it is removed from the truck (see Removal and Installation in post #2). Use the following diagram for this procedure.



Pin 2 at the top left goes to the motor, 1, 3, 4, & 5 go to the switch. What happens is a positive source is routed through a fuse and the ignition switch straight to the motor. The ground for the motor is routed through the fan speed selector switch and in turn the resistor block. When you rotate your switch, you are actually controlling the routing of the motor ground through this resistor block. Notice how if the ground goes through pin 5 then out pin 2 it has to pass through 3 resistors? That would be your low speed. See how there is a direct path between pins 1 and 2? That is your high speed. More resistors, lower speed.

If you look closely at the plug, you can read the pin numbers. Older styles may not have these numbers, so use the following picture:



With the connector tab at the top, pin 1 is on the left, pin 5 on the right.

It may also be on the vehicle side of the plug:



Measure from the following points (you should see approximately the following readings).

pin 2 to pin 1 = 0.2 ohms (very little resistance)
pin 2 to pin 3 = 0.7 ohms (some resistance)
pin 2 to pin 4 = 1.3 ohms (more resistance)
pin 2 to pin 5 = 2.4 ohms (most resistance)

If any of those combinations have no continuity, something is wrong with the resistor block. If all those resistance readings are correct, or you just love troubleshooting, you can do the following two steps by disconnecting the blower motor plug. (Here is what you’re looking for, follow the black and green wires around towards the front of the truck to find the motor plug)



1. Disconnect the blower motor plug (seen disconnected in the following picture, for this step you want the plug indicated by the blue arrow) and connect a wire between pin 2 and ground, then between pin 1 and a 12v source (fuse block, battery, etc…). This will verify the blower motor functions correctly. Notice in the picture the plug is held up by two friction tabs, you can pull down and release those tabs for easier access.



2. Using the following diagrams, and with the blower motor plug disconnected, connect one lead of your meter to pin 1 of the vehicle side of the plug (Red arrow), then the other meter lead to a suitable ground. Verify the resistor block is plugged in to the vehicle harness. Rotate the fan speed selector switch through all the positions and watch the resistance change on the meter (should be similar readings as above). This will verify your speed selector switch and all the wiring has proper continuity. If any resistance reading seems incorrect, and you have already separately checked the resistor block, continue to troubleshoot the speed selector switch and the electrical connectors themselves.






Continued in post #2

[Silver&Blue4x4]

REMOVAL & REPLACEMENT:

First, obtain the part from the dealer or Rock Auto (check this thread for any current discount codes through rock auto. If the current code is expired, don’t be afraid to ask for a new one).

As you look into the passenger foot well, the resistor block will be behind the plastic piece (indicated by yellow arrow in both pictures).





Kneeling down next to the truck with the passenger door open, use an 8mm socket to remove the two screws from the resistor plug. You will end up with this:
(NOTE: your resistor block may not look exactly like this, this is the newer style. Older styles were all black)



Slide the red locking device over, so it looks like this:



Then squeeze the tab on the plug with your thumb while pulling apart the plug and the resistor block.

Install in the reverse order. Plug in the resistor block, slide the red locking tab over, and install with two screws. Perform an operational check of the blower motor and you’re done.




Feel free to add anything you think might be helpful to this thread.

-Ryan

[Silver&Blue4x4]

This may also help if you are still having trouble.

Originally Posted by Jeff

I picked up my new resistor from the stealership, they told me that when they have the same problem they replace the blower motor also (said motor burns out inside and draws more amps). $13 for resistor, $133 for blower motor, $240 for section of harness that melted, and an arm and a leg for labor. I found a motor at a local scrap yard for $45 said they would include plug that I needed. When I picked up the motor I clipped the resistor harness above the motor plug. I got home and got out the multimeter, I couldn't read amps due to blown fuse in meter so I installed fuses inline to removed motors and leads to battery:

Both motors would pop a 7.5amp fuse but not a 10amp (close to the same draw)
"new" motor reads 2.9ohms from wire to wire (old is 0.4ohms)
new resistor reads similar to old (see earlier post)

I disassembled my new scrap of wire to get a good resistor plug and the #2 wire that runs to motor. By carefully removing blue piece inside of plug, I was able to access the pin release catches inside and remove old wires from new plug. Doing the same on the vehicle side, I snapped vehicle pins into new conn. and snapped new #2 wire into motor conn (I didn't have to cut any wires to splice, and my harness is identical to stock). I hope that made sense. My fan works well now and the resistor seems warm but not hot enough to melt.

My theory is that dirty contacts in resistor plug caused heat, that lead to melting, that lead to loss of connection. I replaced fan as a precaution, because I was worried about low resistance of stock fan.

I will post again in a few days to let everyone know if it still works (just cleaning contacts was good for 1.5 days). I hope that by posting my findings I can help someone else with a similar problem or at least a baseline to gather their own info from.

[BLK01DRNGO]

so if the harness that holds the resistor pack gets melted like the one in the picture does the whole harness have to be replaced or can you put dielectric grease on the prongs and everything be fine.

Notice the nice charring on the second pin

[BLK01DRNGO]

I meant the harness not the resistor pack as far as replacing the harness that plugs into the resistor pack I do have some charing on the harness itself.
Also would it be a good idea to go ahead and replace the blower motor while I am at it.

[jixer]

For some reason in the last 2 of these i have done (1. caviler 2.E250 van) the blower motor has gone out shortly there after, but with new resistor packs and blowers they both work great.

Awsome writeup i will be doing the dakota's next week, so thanks. Lowest speed doesnt work hopefully the blower is ok. lol

Also if i had a burnt harness i would go to the junk yard and pull a new one and replace the resistor pack.there is a loose connection in the harness i would imagine.

[BLK01DRNGO]

I really don't have time to get to the junkyard during the week so I was hoping that it would work until I could get to the yard this weekend. This is the wifes truck and she drives it during the day and it is cold out and without heat I am not hearing the end of it.

[Silver&Blue4x4]

Originally Posted by BLK01DRNGO

so if the harness that holds the resistor pack gets melted like the one in the picture does the whole harness have to be replaced or can you put dielectric grease on the prongs and everything be fine.

It's worth a shot, I mean why not try the easy, inexpensive option first? The only thing I would recommend is try to clean the contacts as best as possible beforehand. Maybe try and get some sandpaper in there, or if that doesn't work see if you can get a business card in there, or any type of business card like paper that may be thin enough to squeeze in there yet still be rough enough to take off some of that buildup. Then go with the dielectric grease and let us know how it works. If you don't clean them you'll have a high resistance (or arcing) which equals heat which will eventually cause the same problem to happen again. Good luck!

As far as replacing the blower moter I always thought that was kinda Speaking based on the electrical theory that I know it just doesn't make sense to me. I have heard of a couple people having problems with the blower shortly after changing the resistor though. It's up to you, personally I wouldn't.

-Ryan

[BLK01DRNGO]

Well I replaced both the blower motor and resistor and of course it works like a champ but I was looking at the plug and saw that the #2 that melted on the resistor the wire on the pplug side looks like it took some damage so hopefully I can get to the junkyard this weekend so I can replace that. Thanks for all the input and help this site is great for knowledgable people that like to help others fix problems the inexpensive way.

rep 2 you all who helped me

[opfoto]

Great tutorial....
I just did this repair a month ago on my 2004 DAK. The resistor cost me $13 but the wiring harness was $75. Fried it but good...The harness was melted together and I could not pry it apart. Working great now! Winters coming.

[BLK01DRNGO]

Originally Posted by opfoto

Great tutorial....
I just did this repair a month ago on my 2004 DAK. The resistor cost me $13 but the wiring harness was $75. Fried it but good...The harness was melted together and I could not pry it apart. Working great now! Winters coming.

Have you had any problems since you replaced that wire harness section? I had to order one from the stealership and it is going to cost me $66 which sucks cause now I have to buy another resistor pack.

[opfoto]

No problems as of yet.....Winter has arrived and its working as good as I had hoped. Though the blower motor is loud especially on high coming thru the vents... I wonder if the hoses are routed properly....may wait til spring.

[SHiVMan R/T]

very informative. thanks a bunch.

The very best resistor how-to write-up on the interent!!!!!

[Jarheadoo7]

nice write up mannnn