Chosen Solution
Had an iMac (27-inch, Mid 2010) suffering a power supply failure. Replaced the power supply and now the unit powers on, but the fans run constantly at 100%. Diagnostics show 17 of the 25 sensors (most of them temp, but a couple of voltage sensors) as “can’t read”. Trying to figure out if the sensor failures are due to a problem with the new PSU, or if they are simply a secondary issue that couldn’t be diagnosed until the PSU was replaced. Any thoughts?
Depending on the utility you used here you may need a newer version. What does AHT tell you? Give this utility a try (free version): TG Pro does it report any of the thermal and fan sensors? Don’t forget to disable your other utility before you run this one. All of these sensors are part of SMC services so you could have blown the chip when the power supply went.
