Unexplained shut down of ResMed S9

I have a S9 machine and just started having the same problem of it shutting down by itself. I thought at first that I had forgotten to turn it back on after going to the restroom. If it happened once or twice I would be fine with that, but it seems to be happening every night now. I am going to return mine to the home care company today and see what they say about the problem. I think I will get a Respironics brand instead though. I will re-post after I talk to them.

I only had it happen once in 3 years; but it didn't count. The electricity was off for the whole neighborhood.
The thing that woke me up was the noisy valve on the front of my full face mask.
That lid on the H5i humidifier takes a bit of effort to close,
but it's a good idea to watch the latch move all the way over, and hear the click.

my mother in law has an s9 resmed machine, and while not having the same problem you are describing, it is saying "off" while actively working. If anyone has any ideas id love to hear from you.

My resmeds9 started turning OFF then back ON a few days ago. It happened every 1 to 3 hours. Yesterday I was examining again the connections and buttons etc, and noticed that the SD was not fully seated. It was in the slot, but when I pushed it gently, it went further in and was then secure. After that, the off/on problem stopped.

My conjecture is that for two days the SD card was making partial connection; it was there but not there. Which confused the computer. This is a diabolical problem first because to visual inspection it will look OK. And second because the whole SD card mechanism is delicate and may become temperamental with use. It can become worn and then make intermittent connection, often the case for this kind of mechanism. And third because every time you touch the machine to move it or adjust it, you may jiggle the loose-ish card and change its state.

Constantly used mechanisms are tricky. The main power switch on my old resmeds8 became increasingly flaky with use.

If the problem recurs, I may take some duct tape and string it from the top of the machine to the bottom, pushing in the middle on the protruding end of the SD card just to seat it a little more firmly and stabilize it.

ResMed S9 AutoSet

Hello! I am new, but having the same problems. My S9 is a re-furb that was behaving fine. Then, it just shuts down at random times. Sometimes, it goes back on by itself. No SD card installed. Thoughts?