Possibly detected failing AC


I thought some of you might find this interesting.

My sense is relatively new (about a week) and it had not detected my downstairs air conditioner yet. While looking at the graph I could see the A/C kicking on and off but I noticed something I thought strange, the downstairs AC would spike anywhere from 1 to 4 times before it would actually start. Sure enough when I got home from work last night, capacitors for the compressor blew. No more cold air.

I am assuming this multiple power spike with failing to start was it about to die. I will watch it the next few days after I fix it to see if I am correct and this behavior goes away. If it does go away, there is the interesting possibility that the Sense could warn us of devices about to fail.


That sounds like the signature of a failing runstart A/C capacitor.


I’d be interested to see if it continues to identify it after it’s fixed.


I meant to put in the original message, yes it was the runstart A/C capacitor. I literally just walked inside from replacing it and started the air not 10min ago.

Data point one… multiple spiking gone… I will keep watching it.


@CarlT, thanks for sharing! Device failure detection is something we’ve thought about.

If we have your permission to, we’d love to take a closer look at your data and see what we’re able to see from our end!


Go for it

For the rest of you who may be curious…

It’s pretty wild to zoom out on the graph to where it shows multiple days at once and see the drastic change.
Things of note

  • A lot of those spikes when it was dying are actually multiple spikes back to back, can’t really see zoomed out
  • 17th the solid area is where the runstart capacitors died (2 on this unit)
  • 18th Air fixed right above the “8”


So it continues to pick it up - that’s cool. (Ba-dum-tish)

I had a CFL tube light in my laundry room that was identified a few months ago. A bulb went out last week, I replaced the light, and Sense stopped identifying it so I deleted it in hopes it may ID it once again.



Sorry I didn’t clarify better, It actually never had picked up the downstairs air (The one that failed), I am assuming it’s related to it’s irregular pattern. The above screenshot is the entire house graph, not a specific device.

I am hoping it will pick up the A/C soon as it’s my last major device not detected.


I think mine was first ID’d after a few months - it’s a heat pump. It was only detecting one leg for a month or so, at which point I deleted it because it wasn’t helpful to only detect half the consumption.

After a couple of weeks, it magically found both legs together. Now it identifies a consistent 3750w from the heat pump (there’s still some component missing), about 95% of the time. It gets missed every once in awhile, it’s difficult to parse out why…



Great! I had one of our data scientists take a look and it definitely seems to be a stalling motor. In fact this stalling was interfering with our detection of the AC as Sense was only seeing the motor surge and stall.

I private messaged over a zoomed in shot of this happening, which you’re welcome to share.


Thanks CarlT. This gives us an idea when something may be failing.


Begs the question, Ben - how many of us aren’t seeing appliances detected because of declining health?


I think that’s a fair question. I’d assume not a huge number since appliances last quite a while, but as we look more at fault detection we’ll have a better idea.


My guess is that the Sense will be no help for appliances that are already in declining health. I think where Sense can help is in healthy devices that use to be detected and no longer are because something is wrong with them. Like if I know one of my A/C units turn on but the Sense didn’t detect it (I have notifications turned on) I might be prompted to investigate. Granted this requires intervention on my part but that early intervention could mean the difference between a minor repair and a major one.


I don’t envy the engineer’s job on that one, but it’ll be an exceptional achievement if and when Sense gets there.

@davidferri - I agree. It’ll be interesting as more and more of these instances occur, but especially the ones where something is identified reliably and then becomes unreliable.


That’s pretty interesting. You can see how long the Compressor stays locked out on thermal overload until it tries to restart, most likely due to overheating. This is pretty valuable information for those of us that haven’t had any Compressor issues thus far.
You may want to consider having an insulation test performed on the Compressor. It could be directly related to the capacitor issue. Over time the insulation may leak and cause several issues including acidity & moisture problems. This leads to a number of issues, capacitor failure being one of them. It’s likely this may be a lead to another issue. Many people just replace the faulty capacitor without giving any thought to why it failed, but they don’t usually fail without reason. If the insulation is leaking, having it tested could save you an expensive fix in the future.
Things are looking brighter.
Sense is definitely getting better IMO :sunglasses: