Following up my previous post...

I only completed setting up the new UPS and charging the battery the day before yesterday. That night was the first time I connected my iMac to it. I then performed the “smax013 test” (unplugging the UPS). It performed as expected (I received a small dialog box indicating that the iMac had been connected to the battery, and that I should consider an expeditious shut down).

Because I have the Energy Saver set to shut down the iMac late at night, each night ends with the iMac shut down. However, since plugging the iMac into the UPS, I discovered that after the iMac shuts itself down, the UPS begins to make a “clicking” sound every 10-15 seconds (as if it were switching on and off). The sound continues to repeat itself until I turn on the iMac.

I’m a bit concerned that this may be part of the “switching problem” that we’ve been taking about. However, it happens only when the iMac is turned off (but the UPS still is plugged in and receiving utility power), which seems contrary to the condition described by the APC tech. (In other words, the UPS is not being told “Hey, we’ve lost utility voltage, and the iMac is ‘on’ and needs power.”) Moreover, the previous unit (BE550) didn’t exhibit this behavior (it was always quiet). So it may instead be a defective unit.