2010 F150 XLT, Ext Cab, 4X4, 4.6L 3V

Whenever, and each time I turn on the blower motor, a horrible hot/burnt electronics stink fills the cab. It does not matter if AC, heater or just vent.

There's no smoke and after about 3 - 5 minutes, the smell goes away.

I smell nothing under the hood, or outside the truck. I can find no burnt wires, no blown fuses. Everything works.

My first thought was the blower motor, but decided to replace the blower motor resistor first, since that is much cheaper - and, being no spring chicken, easier for this old man to get to. No luck.

So I replaced the blower motor. But that still did not fix the problem.

I am at a loss as to what could be causing this. I cannot think of anything else that would be in the ductwork - except the resistor and already replaced that. I have to assume the blower is sucking in the smell from something else, but don't understand why I can't smell it under the hood.
Also confusing (for me) is why do I only smell it when the fan is turned on? It seems to me, if something else was getting hot, especially if coming from inside the cab, it would smell at other times too.

Any ideas?

 

did you make sure the connector for the resistor wasn't melted

 

Thanks for the quick response.

Yes, First thing I checked when I unplugged it from the original. It was nice and shiny - no signs of heat.

I guess I should add I'm a retired air traffic control radio communications technician - so I know "that" smell well. My biggest problem is 70 year old eyes and body.

I am willing to take it to a shop - unless the suspect part is as easy to access and replace as the motor or resistor. I would just like to point them in the right direction first.

 

My carrier field included electronics and I'm familiar with the smell. When I first read stink in your post the first thing I thought was mildew odor from condensation left on the evaporator from not airing it out. Quite common. Not questioning your smell capabilities but is it possibly that what you're smelling?

 

I am confident it is not that. It is not a musty, moldy smell - but that very distinct electronics smell. And it happens if the AC is on, or not. It is quite strong for the first minute, then quickly fades away.

Plus, I've been a long time allergy sufferer (took allergy shots for 35 years even), with grasses, trees, weeds and molds as my allergens. And I get no sense (pun intended) of any type of allergic smell, runny nose, itch, watery eyes, etc.

 

Any ideas on where to ask and get more ideas?

 

Since this smell is connected to the fan, no matter which mode, I’d pull the HVAC control panel and give that a good looking over.

If this truck hasn’t been only under your ownership, there’s no telling what kind of hack job was done to power some other accessory.

 

Thanks for your reply. I bought it new so only me for ownership and never out of my control.

Are you talking about this whole unit? Not sure I know how to take apart the dash to get that out.

What still really confuses me is the smell only lasts for about 3 - 5 minutes once I turn something on that requires the fan (AC, heater, air only), then all is fine from then on - until I turn off the truck again. I wondered if it was me just getting used to the smell so I asked my neighbor to take a whiff after I had come back from the store and it had been running for about 20 minute and she said she didn't smell any burnt or unusual smells.

 

The blower motor resistor will heat up when in use. Sounds like maybe something is burning off when it does.

Have you had COVID? Apparently, it makes certain normal smells become terrible smells.

https://www.healthline.com/health/we...-in-nose-covid

 

Except as noted in my opening post, the blower motor resistor was the first thing I replaced. That did not fix the problem. So then I replaced the blower motor. Still did not fix the problem.

​​​​​​​No COVID here.