Sense Helped Diagnose Bad A/C Compressor Fan

I happened to be checking the energy monitor today and noticed something off when the upstairs A/C unit kicked on. Watts usually jump and level off, but today, they would jump like normal, then continue to climb several thousand watts. Then drop off after a while. So I took my phone out with the monitor on and started the unit up to see what was going on. Unit started up, compressor started, but the fan did not immediately start up. I could see it trying to move, but it was not getting going. Finally started up and found it to be very hot!! Turn off unit and tried to spin the fan freely, but could feel a lot of resistance. Motor housing was extremely hot.

Installing a new motor tomorrow.

Don’t think I would have noticed this anything amiss without the Sense monitor until it failed completely. Could have been bad if that motor overheated even more!



I don’t know about the rest of the Community, or the Sense brain for that matter, but I see those waveforms and immediately think “That ain’t right!”.

Sense will want you data.

Could have very well saved you from a fire. :fire:

That ramp is pretty wild looking!

As @ixu noted, we’d love to take a look at your data for this as we’re working some possible fault detection algorithms for HVAC. Is it ok if I pass along permission to the data science team?

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@RyanAtSense. Absolutely. Feel free to use the data as you see fit.

Installed the new motor and capacitor this morning. Everything looks good now. Could barely turn the old motor. New motor spins beautifully! 30 minutes for the install. Pretty easy.

I think Sense definitely just paid for itself. Saved me someone coming out to diagnose the problem. If the motor continued to full failure and seized, it could have caused serious problems and additional costs.


I’ll pass it along.

That’s great to hear! If you’re so inclined, and feel like you can estimate the cost savings, we’d absolutely love if you shared your story at this Community’s sister site,


I am guessing that the “ramping power usage” while the failed unit was running was actually your AC compressor working harder and harder to suck against low pressure as the condenser does not work right without airflow over it to condense the refrigerant back into a liquid.

I wonder if the drop you see is it kicking off due to thermal overload? Or some other sensor shutting it off due to pressures being out of whack?

Having a Sense is great to be able to watch this stuff work! I use mine all the time for this!

if the condenser fan quit then I would expect the load to be less as it would be easier to compress the Freon. If the evaporator fan quit then I would expect the load to increase along with the indoor coil to freeze.
If @marc is still around, he’s the expert on this.