2005 TJ - only speed 3 and 4 on my fan / AC

[TerryMason]

My TJ has 4 settings for it's interior fan (or well, it did). Now, only speeds 3 and 4 actually do anything.

What's the best way to troubleshoot this? I assume it's either the switch or the motor itself, but I'm not sure how to go about diagnosing this.

 

[TerryMason]

A quick look on ebay, and the switch is $150+, while the motor is only $40
https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2334524.m570.l1313&_nkw=05+wrangler+fan+motor

I'm tempted to just throw a motor at it and see if that fixes it.

 

[JPNinPA]

There is a resistor block that fuses open. It is located behind the glovebox.

This hysterical. On my way to work I turned my fan on defrost. And thought about this resistor. My recommendation it to always turn the fan on or off on the high setting. The high setting is a direct short in the resistor pack allowing max current for start. And least likely to blow out. If this doesn't work it's the melting connections or the fan itself.

The reason the resistor fails is due to two factors. One is an electric motor by itself when starting may draw a spike of current instantaneously then drop in a decay with a second or so. This high current can fuse open a thin wire or thin bent wire. Second the resistor is a serpentine run of metal printed line. The lines width and length changes the resistance. Thinner is higher resistance resulting in slower fan speed. Because current of electrons running through the flat lines takes a path like a race car on a track. Tight on the way in and fan around the bend. Do this for some time and the metal starts to migrate away creating a thinner wire. This is called electro migration. There is more going on but this is the simple version. Now thin the wire enough and the starting current blows the wire open.


Regards,
JPNinPA

Never look down on anybody unless you're helping them up. -Jesse Jackson

 

[JPNinPA]

2005 JEEP WRANGLER 4.0L L6 Blower Motor Control Module / Resistor | RockAuto


Regards,
JPNinPA

Never look down on anybody unless you're helping them up. -Jesse Jackson

 

[mark sr]

Before the blower motor went out on the XJ I used to have it would struggle to turn on the slow speeds but worked on high [or was it the other way around??] Anyway by the time it got bad enough to replace it would only run on one speed. Replacing the motor fixed it but your issue sounds different.

 

[TerryMason]

It's fixed! JPNinPA, you were right on the money. I bought a BWD brand Resistor (part RU1045) at Advanced:
BWD HVAC Blower Motor Resistor RU1045: Advance Auto Parts

Popped it in, and now I have all four fan speeds! Thanks again, that was an easy (and cheap) fix

 

[TerryMason]

This video seems to be accurate

 

[JPNinPA]

It's fixed! JPNinPA, you were right on the money. I bought a BWD brand Resistor (part RU1045) at Advanced:
BWD HVAC Blower Motor Resistor RU1045: Advance Auto Parts

Popped it in, and now I have all four fan speeds! Thanks again, that was an easy (and cheap) fix

Yay!
You fixed it!

I’ll bet if you look at the old one you could see the burn mark where the metal line popped.
The lines and board are dipped in paint to protect from moisture. Where it failed probably looks like a paint spit.


Never look down on anyone unless you are helping them up - Jesse Jackson