New 24" M1 iMac doesnt turn on without earth ground

Older Apple products could be used without a grounding pin. Apparently, the new iMac requires it. To quote "Important safety information for your Mac":

WARNING: Your AC cord has a three-wire grounding plug (a plug that has a grounding pin). This plug fits only a grounded AC outlet. If you’re unable to insert the plug into an outlet because the outlet isn’t grounded, contact a licensed electrician to replace the outlet with a properly grounded one. Do not defeat the purpose of the grounding pin.

That sounds pretty unambiguous.

Randy Weber wrote:

I also tested the electrical outlet with a pocket electrical outlet tester, similar to mentioned above. The tester showed OPEN Ground with the center tester light illuminated. The interesting thing is, the new imac did work on a different outlet downstairs that also showed an OPEN Ground, according to the tester. So the tester wasn't able to identify the particular different quality that exists between the two outlets. Also, FYI, the client has a 2013 imac that works perfectly on the same outlet that the new imac doesn't work on. Agreed, the solution is proper grounding. Which might not be economical viable for this client.

At this point, that receptacle could be worn out or damaged and that particular cord does not fit tight enough to make a good connection. Worst case, there could be a loose wire on the back of that outlet or a loose/week connection somewhere else in that circuit.

At minimum, your client should have an electrician check that circuit and/or replace that wall outlet.

It’s probably detecting a potential difference between the neutral and the ground pin, which is a very bad thing, and not just for Macs. That needs to be fixed; its very dangerous. Either the wiring is reversed, or there really is a ground fault. You need one of these:

Maybe there is a voltage or current issue with this house or neighborhood. I know one of the places we lived years ago had intermittent power fluctuations from the electric company. I remember my father putting a meter on the line to monitor the power we were receiving from the electric company as it tended to be either very low dips or very high spikes IIRC. Maybe there is something else on that circuit that is interfering with the power that is going to the iMac on that outlet. You may want to monitor the power to the electrical outlet in question to see if the outlet for the voltage & current over time. Sorting out the electrical issue in the house should be done especially if the iMac will work on another outlet elsewhere in the house, but maybe a power line filter may help to even things out or maybe use a UPS until the bigger issue is sorted out.

I just checked my outlet. Hot and neutral are reversed. The bad part is, I think this is an outlet I replaced with a GFCI, so it might be my fault. 8^(

(We got the house a few years ago and the previous owners had replaced the two prong outlets with three prong without regard to grounding.)

Keith Barkley wrote:

Just tried it with another outlet - this one shows just the open ground fault. (Single middle light) and the iMac works fine there, too.

Laurence Finch: I prefer the tester that has the GFCI test button with the trouble lights.

I can understand that. I have other testers also, but the one I posted is an inexpensive basic one that you can carry in a pocket.

The M1 iMac comes with an external power supply so comparison with prior model iMacs is n/a. Be aware that fooling the grounding is ill-advised not only because of obvious safety reasons, but also

• knowingly avoids Apple’s warning not to defeat the grounding pin which has consequences on the warranty and
• could be overridden by Apple with a future upgrade assuming some of the logic is built into the firmware
• has further consequences on liability in the case of accidental shock

In other words, there are no good reasons to seek a solution/discussion along these lines. Good intentions yes, reasons no. All the best!

Same requirements for the previous 2013 iMac that was plugging into the outlet.

https://support.apple.com/kb/sp688?locale=en_US

Electrical and Operating Requirements

• Line voltage: 100-240V AC
• Frequency: 50Hz to 60Hz, single phase
• Operating temperature: 50° to 95° F (10° to 35° C)
• Relative humidity: 5% to 95% noncondensing
• Operating altitude: tested up to 10,000 feet

👍 No “cause” other than enforcing safe electrical practice, not to mention keep warranty costs under control. The electrician will be happy to explain…good day.

👍

Yup' I was thinking the same thing.

Our home was built in 47 and the old un-remodeled sections still have polarized wall outlets. Fortunately all of our original wiring was done with that hard to strip 2 wire sheathed cable (where both the hot and neutral run back to the box) instead of knob and tube.

I live in Albuqerque with the same lack-of-ground issue, and mine works fine without a ground, though my grounding is kind of random, I need to see if the particular outlet I am using is grounded or not.

Just tried it with another outlet - this one shows just the open ground fault. (Single middle light) and the iMac works fine there, too.

Laurence Finch: I prefer the tester that has the GFCI test button with the trouble lights.

Keith Barkley wrote:

Just tried it with another outlet - this one shows just the open ground fault. (Single middle light) and the iMac works fine there, too.

That would be the correct polarity with a missing ground.

All modern replacement Receptacles and GFCIs are coded with a brass screw for the hot (black) wire and a silver screw for the neutral (white) wire.

Plus as I mentioned earlier, the narrow slot/blade is hot and the wide slot/blade is neutral.