I appreciate the reply, @alphanumeric
As I tried to say in my post, on one of my PIs, the LED comes at some point after it is booted and then stays on. It does that with no software installed; and it does that with the software modified to rip out all support for the button and LED (I have that on github here: https://github.com/chaunceygardiner/fanshim-python/tree/just-the-fan-man). Note: it also replaces psutil for getting the temp because psutil does not work correctly with the DS3231 RTC.
I have a total of five RasPi 4s and four of them work without software running with the fan running continuously. They also work with the software, turning on and off as expected, with the modified software I mention above.
The last Pi, the only one with 1-wire turned on as I have some temp probes hooked up to it, works; BUT the LED comes on; I think always within the first 10 or 20 minutes, and then stays on for the duration. This is true with —noled specified in the original software, with the modified software and with no software running. It’s not likely the fan shim as I bought another and I still see the same behavior.
Since I have an extra fan shim, this morning I snipped pins 8 and 10 (i.e., BCM 14 and 15). It was easy enough to do. I figured I would still have contact as I saved pin 12. The fan doesn’t fit nearly as tightly as it did before; but it appears to have solved my LED problem.
Here is a photo. Look closely to see the snips so that pins 8 and 10 don’t make contact:
I’ll post another photo where it’s easier to see in a follow up. I’m a new user and can only include one photo in a post.
These pins are being used for the GPS (https://pinout.xyz/pinout/ultimate_gps_hat). One would think that something in the GPS communication (NEMA sentences) is causing the LED to turn on, but all five of my PIs have GPSs. The offending PI’s only hardware difference is the 1-wire.
Pimoroni, how about a dumb fan shim?