Aquatec Booster Pump Auto-shut-off stops working in late spring, works again in fall?

[siege]

Okay... so, weirdest thing. I have an Aquatec booster pump with the auto shut-off switch installed. It worked fine for the first while I had it. Then it stopped working. I didn't have time or attention to mess with it and just dealt with having to unplug the pump every time I was done making water.

Then, in the late fall, it started working again? I noticed the sound die away one day when I turned the flow off... and it was off. Not trusting it, I unplugged it anyway. But after a few more uses, it was still working consistently, just fine, since... November, or so? And then, just a week or so ago... it stopped working again! Several uses of it since, and it still fails to cut off.

Thing is, my water pressure at the input to my RO/DI unit isn't significantly lower, still reading about 70psi when the pump is running, the same as it has been the last few months.

The only thing I can even guess has changed is that the cold water coming out of the tap is now warmer than it was? Could the shut-off actually be sensitive to input water temp? Does anyone know if there is a way to correct this? Or has anyone else even experienced this same issue?

 

[The Quilted Reef]

Do you have an automatic sprinkler system?

 

[siege]

Do you have an automatic sprinkler system?

I do not, unfortunately. Good thought tho... and wish I had one. These last two weeks I've been running around the yard every 30m from 7pm to 10pm or so dragging around a sprinkler.

But no, it's never been on when I've been making RO/DI water. The room where my RO/DI unit is is also the primary wet-wall in the house, right where the water comes in, and I can hear in there any time water is running to anywhere else in the house.

It really is the oddest thing that - granted it's a limited set of data points - it seems to be tied to the season somehow... but I'm at a loss for a good reason as to why even a slight change in external pressure (which this auto-shut-off valve, being connected only to the output, not the input, never sees anyway) or a small increase in the temp of that water (from ~62ºF to ~66ºF) should keep it from working properly.