When speed 3 is selected the blower runs at the same airflow as speed 2. Is the resistor, switch, or something else the primary candidate? Speed 1 & 4 are normal.

 

Resistor, it's a $23ish part and takes about 2 min to replace, do a search for it someone has a nice write up on doing it

 

Well you lucked out on my boredom

https://www.f150online.com/forums/ar...emtc-hvac.html

 

Thanks for the link, it looks like a bad switch.

 

did you already try the resistor and no change?

 

No I haven't changed the resistor. From what I read on the link provided if 2 speeds in the middle are the same it's the switch. I may just order both parts, the resistor is only $13 at rockauto. I'm ordering a bunch of other stuff so not much additional shipping cost.

 

I will bet on the resistor still. Mine had 2 and 3 the same speed then I lost 2 so 1,2, and 3 all blew like it was on 1 but it took a couple weeks before it went to all 3

 

Switch fixed it. The plastic around one of the terminals was partially melted. Ohh well, I now have a resistor for when it finally gives out.

 

Mine use to work just fine, but one by one have all gone dead.
Except 4. It blows like a bat out of hell...

I pulled the resistor and with it unplugged, nothing changed. 1,2 and 3 do not turn the fan on and 4 blows like it should.

I'm assuming that could mean the switch is bad.

I have an aftermarket stereo head unit, and don't have the keys handy, so I didn't get the deck out yet.
Is that where I go in to get at the fan switch?

 

Is this the switch?
It's called the blower switch.

 

The switch looks just like mine. No radio removal required to replace the switch, just pull the trim piece and remove HVAC control. Once control is out remove switch. The resistor could still be your issue, especially since it does the same thing if it's connected or not. I suppose you could ohm out both parts to find out which is bad, but since they aren't that expensive I just ordered both.

 

Excellent info.
Gotta love this forum.

 

Swapped out the resistor today and all levels work again.

Thanks again.

 

Settings 1-3 on mine are done. 4 works full blast.

Resonator? Or Switch?

 

I finally found that mine was the contacts in the switch were dirty, I wiped them off and it was back to normal