Burning/electrical smell

I'm thinking it's from the HVAC blower motor - does this sound possible?

 

Had a strong odor of electrical burning from the vents. When I managed to look under the hood there were no strange smells. Couldn't detect any odor anywhere else in the car. Started the HVAC fan and had the smell again.

 

After things cooled down a bit I popped out the fan and flipped open the small access flap that exposed the motor windings and I could detect a faint hint of the previously strong odor. Also disassembled the power transistor that runs it and it appears to look/smell fine.

 

Drove home without the fan connected and the HVAC set to fresh air with the windows open. Didn't notice anything else strange.

Yes, that sounds possible. You probably have a fan that's about to die.

Is your blower motor making any weird noises? That burning smell may be from your blower motor wearing out. I'm not sure exactly how they're built, but that seems like the most likely cause.

 

They're really easy to get to.

 

That's just my best guess.

Nope, no funny noises from the blower. Fan turns freely but with a little resistance which I assume is just the motor brushes.

 

I took a good look around, didn't see any damaged/melted connectors. Used an inspection mirror to see behind the relays on the right side of the car under the dash and all looked fine. Took another look under the driver side dash and it too looks OK.

 

I've noticed a similar smell in the car before a few months ago, but it was stronger this time. I have the A/C or heat on all the time, never a moment when the blower is off. Just seems strange that it would be such an occasional problem.

Do all of the fan speeds work correctly? I've had other vehicles burn out the resistor pack for the fan speeds cause a smell like that.

Yep they do. As mentioned above I disassembled the power transistor pack that runs the blower and all looks/smells fine.

Still getting this... any other places to look before I tear everything apart? I could smell something about an hour after turning it off the other day, so it's not oil or anything on the exhaust.

If you are smelling ozone, which is the typical electrical arcing smell, it is caused by sparks. The only way an electric motor can spark is if there is not enough conductivity betwixt the brushes and commutator. This is assuming a conventional DC motor, of which blower motors generally are. That means the brushes are worn and not making good contact - or the commutator itself is just worn out. As for the brushes, these are generally replaceable parts. BTW, the problem can be exacerbated if the rotor isn't moving freely. If there's a slight drag this tells me the lubricant packed into the bearings (usually friction bearings) is drying out - or gone. When the motor spins things get hot and friction increases.

 

There are other failure-modes but check this first.

I replaced the blower ages ago. I don't think it's ozone I'm smelling.

Still getting this from time to time. Any other thoughts on what it could be?

Strip the dash