Blower motor come on at high speed, even with switch off!

[WarPig2011]

Ok, I’ve spent the last hour searching the net for an answer with no luck, so here I am...

I have a 2016 Expedition XL. Last fall I replaced the blower fan resistor because the fan would not come on. This summer, I had a couple of glitches with the fan cutting out, but re-attaching the wiring plug seemed to help. The past week or so, when using A/C or just the air circulation, the blower would hiccup for a second or two and blow at full speed. Today it went nuts: all of a sudden, fo no reason, the blower would run at top speed. The control knob did nothing; not even the on/off switch would stop it. Turning off the ignition stopped it running. I start it up drive for a bit, and the save thing: it will blow at full speed, even with the switch off or the speed control knob at minimum.

Any ideas?

 

[WarPig2011]

Crickets. No one has any ideas/fixes?

 

[Trainmaster]

Not sure how the 2016 XL is controlled, though the base models usually have minimal controls. Some models operate the heating fan at full speed if the engine is deemed to overheat. With the proper code reader you should check the coolant temperature that is being read by the vehicle computer. A bad temperature sensor can create this problem.

Another cause could be a short or ground in the heater motor resistor or its wiring.

Lastly is a controller problem as even the most basic controller is computerized and capable of strange and inconsistant behavior. If you don't have the shop manual pinpoint troubleshooting routine, you can try replacing the controller with a junkyard one from ebay.

 

[Hamfisted]

Inspect the harness plug there at the speed resistor for heat damage. Does the fan still run if you unplug the speed resistor? It wouldn't be that uncommon if the resistor cooked off again. What brand was the one you installed ?

 

[99WhiteC5Coupe]

Ok, I’ve spent the last hour searching the net for an answer with no luck, so here I am...

I have a 2016 Expedition XL. Last fall I replaced the blower fan resistor because the fan would not come on. This summer, I had a couple of glitches with the fan cutting out, but re-attaching the wiring plug seemed to help. The past week or so, when using A/C or just the air circulation, the blower would hiccup for a second or two and blow at full speed. Today it went nuts: all of a sudden, fo no reason, the blower would run at top speed. The control knob did nothing; not even the on/off switch would stop it. Turning off the ignition stopped it running. I start it up drive for a bit, and the save thing: it will blow at full speed, even with the switch off or the speed control knob at minimum.

Any ideas?

https://static.nhtsa.gov/odi/tsbs/2019/MC-10163573-0001.pdf

 

[07mustangman]

Blower control module behind glove compartment. That's what my problem was with my 2011 Limited.

 

[OR_Limited]

I have been having the same problem. Mine is a 2013 Expedition EL Limited with the heated seats on the hvac controls module. First my front blower went out. I did a manual test of the blower and it worked fine. I replaced the relay. The next day it stopped again. I replaced blower resistor. The next week it stopped again. I replaced the plug and traded the resistor in on o’riely lifetime warranty. After that the blower worked great. So well that it will not turn off. I took it to the dealer and they diagnosed the hvac control module. The console control with all the buttons. Sadly there are none to be had in the whole country. I ordered one used which should arrive this week.