My fan in my Tracker had randomly stopped working... for no apparent reason.  Sometimes only on certain speeds.  Sometimes nothing at all.  My fan motor had been making a "putting" sound when on the low setting so I figured it was getting to the end of its life.  I had ordered a replacement from Rockauto.com a couple months ago anticipating this.   

I suspected it was the blower motor but I also ordered a new blower resister to swap out the old one too.  I read that the older the motor gets the more it draws electrical current and this gives the resister fits.  So I installed the new resister.  Nothing.  Got the fan motor in today... and I have air circulation again AND my A/C back... AND the new fan motor is probably circulating another 25% more air to boot. 

My Tracker cools down quicker now.  The A/C still isn't as good as on a Honda CRV, for example, but it is better than it was before and the A/C knocks down the humidity and cools the truck quite nicely.

Money well spent IMHO.

if the blower resister goes, the blower will only work on the highest speed. the main thing that go in the resistor pack is the thermal fuse. i bought a bunch of them on ebay for a couple of dollars. the only thing with installing them is, you have to use a low wattage soldering iron and solder them as quickly and with the heat on the resistor side. to much heat and you will blow the new fuse.

id keep that resistor for a spare. a lot of people around my area with chev pick ups carry a spare in their glove box.  they are famous for going.

HEATSINK.

Get a pair of needle-nosed pliers and a large rubber band (or hemostats if you have those) and clamp the lead to the thermal fuse between the fuse and the solder joint and then solder the joint - it's also better to use a higher wattage soldering iron because you can make the joint faster, less time generally meanst less thermal energy gets conducted to the fuse.

I think the blower resistors go BECAUSE the fan motor is worn.  The resistor is only a symptom of the actual problem.  I think in most cases IF the fan motor is good, you shouldn't be blowing resistors.  So when you have a blown resistor, replace the fan motor along with it and see if your resister goes out again any time soon.

I just bought a used Jeep today.  Yep!...  I sure did.   I drove it several hundred miles bringing it home today.   The Jeep's fan blower switch only works on the the 3rd and 4th setting.  Nothing on the 1st and 2nd settings.  I'm going to replace the resistor and the fan motor and see what happens, short term and long term.  For a Jeep both items will cost me around $50.  I'm betting I'll get even MORE air circulation from a new fan blower motor on the Jeep too.

I think the blower resistors go BECAUSE the fan motor is worn.  The resistor is only a symptom of the actual problem.  I think in most cases IF the fan motor is good, you shouldn't be blowing resistors.  So when you have a blown resistor, replace the fan motor along with it and see if your resister goes out again any time soon.

I can't agree with you on this - resistors are passive components - they fail primarily due to overheating or excessive current - and in this scenario the resistor is the device intended to limit the current, and thereby the speed of the blower motor.

The low speed settings are most commonly used and with repeated heating cycles they will eventually fail - I've had a few fail and never replaced them - I just switch to the next lowest fan speed that works.

I can agree with that, so let me modify my statement to say I think IF your vehicle repetitively blows resistors within increasingly short periods of time, the issue is more likely your fan motor being old and excessively worn and is drawing excessive amperage causing the premature failure of the resistors.

higher temperatures means more thermal energy gets conducted to the fuse. using a lower temp on the resistor side to get your solider flowing then put your thermal fuse on to the solider. less heat transfer to the fuse. if your theory is correct they would teach every tech to use soldering guns on sensitive circuit boards.   

I'm going to assume you're responding to my earlier post...

First - please don't confuse a higher wattage soldering iron with higher temperatures - they are not the same - whatever the iron used, you must get the joint up to 361*F or the solder will not melt.

Second - please research how solder guns work so that you can learn the true reason why they are not commonly used for circuit board repairs - you'll find it has very little to do with the temperatures involved.

Very briefly - a solder gun is essentially a transformer with a single turn secondary winding - the heat is generated by the high alternating current flowing through that single turn secondary, and that is where the danger to sensitive electronics lies.  You're literally placing an uninsulated wire conducting 40~50A into direct contact with whatever sensitive electronics you're repairing - not very smart.

Third - the technique described is poor - the joint should be mechanically sound BEFORE the solder is introduced - every tech should have been taught that very early on.