Central AC Unit won't turn off from thermostat & burning smell emits

[zannej]

Title doesn't accurately describe it. Heat has been working fine the last few nights but last night it didn't turn on. It got down to 56° when it's supposed to heat to at 64°. I pressed the Mode button on the thermostat until it went to Heat. After a few moments, I started to smell a strong burning smell. The kind I smell when the timber company does a controlled burn. The air in the kitchen looked foggy to me, but that could be because my vision is a bit blurry this morning. I then set Mode on thermostat to OFF, but nothing happened. I've had this issue in the past where OFF does not work on this thermostat. It's also very hard to read the LCD screen. Anyway, I went and flipped the breakers just in case something had ignited. I alerted my brother and mother that we might need to evacuate. My brother woke up and said he could smell something burning too.
I got him to get the ladder for me (for some reason I'm not able to lift things today and I don't know why) and then he held it steady so it wouldn't tip while I climbed up (it's too short so I have to stand on higher rungs than they recommend). I'm still too short to see much, the access panel fell down, and when I used my phone to try to get video it didn't show much- focus got stuck on something close up and the flash didn't illuminate as far as I wanted.

You can't see it, but the cord goes to a lightbulb and there appears to be some sort of attic fan facing the ceiling, but I don't recall seeing a duct for it from on top of the roof so it may be covered up.

Nearest duct to the right goes to my room, silver duct goes to Mom's bathroom. Not sure about duct to the left.


I can't really tell what this vertical thing and white spot are. I couldn't see it from the ladder.


I think this is the duct going to my room.


I know, ducting pics probably don't help. But man, it's cold in here now.
It didn't smell like electrical fire. I'm about to change the filters but I'm worried that we may need a new capacitor again.
The past few nights when heat came on it didn't have this smell.

 

[zannej]

One detail I forgot to mention: I am not certain because my vision sucks, but I think the "heat" setting on my thermostat might have the letters EM in front-- for Emergency Heat? It is off right now so I can't see. Could that be why it had the burning smell? Using heating elements it doesn't normally use?

Still not sure why the regular heat is not working though. I'll turn breakers back on after I change filters and cycle Mode to auto.

Eventually, I'd like a better thermostat but I don't think mine has the right wires for fancier ones.

 

[Guzzle]

Maybe the dust is burning off the heating elements.

 

[zannej]

Guzzle, that's what it must have been since it was the Emergency Heat rather than normal heat. I changed the filters and cleaned the grilles thoroughly. The grille in my brother's room was filthy (I don't go in there often as I can't see well and he has trash all over his floor). In the past I've had to pull plastic bags off the grille in his room.

After thoroughly cleaning everything & getting new filters in, I turned the breakers back on and the heat started working.

 

[zannej]

I know this issue has been resolved, but I am adding the picture of the old capacitor so I can find it again bc I can't seem to find the post where I had it before. It has two prong thingies on top but I just took a picture of the label.

I have to order a replacement I think.