Hi All,

I've got a 2006 F150 King Ranch, and have had an issue with the climate control for months now. The blower motor is stuck on high. I have replaced the blower motor resistor under the glove box 3 times, each time the symptoms are exactly the same. First truck start, i have full control of HVAC fan speed, second start, it either goes back to being stuck on high, or doesn't come on at all. when its 'working' and stuck on high it takes about 3-4 minutes for it to actually come on; the temperature adjustment works (it regulates the warmer/cooler adjustment of air) but fan speed adjustments do nothing. I am able to change between defrost, turn ac on/off, and the vent selectors work as well.

What could be causing the blower motor resistor to fail? What else can I look into?

Cheers

 

My guess is a bad blower fan motor . I have changed mine a long time ago ,it's not real difficult . Motors draw max current at stall or locked rotor . If it doesnt turn it wont reduce current draw, plus I would think the fan motor cools resistor unless the path is blocked . So yes you could have something in there blocking flow or possibly hindering start of rotation all kinds of stuff can get in there . Bearings/bad wires weak -connections
The aftermarket assembly is not very expensive . Maybe someone will have some better info or better ideas.
Mine was very intermittent coming on so I had no choice . Good luck and let us know your fix .

 

There is an aspirator tube that is supposed to cool the thermal limiter in the resistor block
That tube hooks to the blower motor and goes into the case (about an inch in diameter short hose)
It cools the motor brushes and puts air past the resistor
That tube may be blocked or missing / fell off
That is the only thing I have seen for repeated failure of the resistor block
The thermal limiter is replaceable
Cut the old one out and solder another one in
They used to be available thru Radio Shak for about 10 bucks for a package of 2 or 3
Once you solder another thermal limiter in there, you are liable to never have another problem as the new thermal limiter is a bit more robust
Good luck

 

A King Ranch trim (add-on to the Lariat) should have the automatic climate control as standard which means it does not have a resistor with a thermal fuse, it has the electronic blower speed control module instead. Many parts sellers and "old-timers" use the terms interchangeably which isn't very accurate.

Aftermarket modules seem to have a sketchy history. If you've been using them, recommend going back to Motorcraft. If all of the replacements have been MC, then inspect for airflow obstructions through the module's cooling fins. If that looks okay, then replacing the motor also is recommended.

 

I have the automatic climate control. But this poster seems to have the resistor version . I really don't know how you get these different setups , I like my climate controlled lariat but I have had to change blower motor once.
My wifes cressida had a blower motor that you had to bump dash to start it moving , ac guy said it was too expensive to replace -keep bumping it. Well she was going down the road and smelled a plastic trash fire , she soon found it was her car she pulled over saw burning in dash where motor was. She saw fire spread ,throwing her stuff out on the side of the road it soon turned into flames 20 foot into air . Complete loss . So it can turn bad . She loved that car, now she has a ford explorer . She thought I would put up with another high priced cressida parts eater - nope no more $800 parts for fuel pump /blower motor/ sky light motor.

 

Don't think so. If it were a manual, it would be "only works when switch is on HIGH setting". "Stuck on high" implies it operates on high speed regardless. Besides, it's a KR and those came only with auto climate.

Not a Ford....

 

Yea, it's a king ranch with auto temp control. I have been using the non motorcraft brands, I'll switch to motorcraft, but did order a blower motor just 8n case. What's suspicious to me is that it works correctly the first time the new resistor pack is in, then the next time I start the truck it fails. So the motor is capable of turning a lower revs
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I take it the hose the other poster mentioned is not applicable to my truck? I don't recall seeing anything like that up there.

 

Yeah, I've never heard of or seen that on these Fords. The module, whether electronic or old style resistors, is just placed in the plenum where airflow from the blower cools it.

I'd replace both at the same time, something I rarely recommend. However, since those electronic modules are expensive, I'm making an exception to my normal recommendations.

As I mentioned, the aftermarket blower speed modules have a sketchy history. Your experience is not the first to be reported.

And remember that you do not have a "resistor" in your system, it's a lot more complicated than that.

 

Yes I know it's not a ford , just told this as a caution for what can happen . Motor arcing can cause a fire , stalled motor can cause high currents .

I would say its not wise to use an aftermarket speed control since he has already lost three units . Of course a bad motor could cause the burn out. So I would replace both . My auto climate control had no problems with aftermarket blower motor .

Most fan motor controls hit high first in order to get motor moving so it will not stall . But this is another animal .

 

Finally an update here; I installed a new blower motor and an OEM speed control about 2 weeks ago now, and so far so good on my speed control working. Uncertain if it was the OEM unit vs the crappy off brands, or the fan was actually causing it, either way I'd love to meet the engineer who put the fan there...

THanks all !