Since a week my iMac, running Snow Leopard, behaves strangely in two ways:

First, I always unplug the iMac when I don't use it. Now, when I plug it in, it immediately starts, without me pressing the On-button.

Second, after booting, the date and time are 1st of January, 2001, midnight. Several programs complain instantly. The IP address is something strange, certainly not the usual 192.168.X.Y address. As internet access, I use a network cable connected to a Devolo home-plug (connected to a fibre glass modem).

After two minutes of waiting, the iMac gets a normal IP address. One minute later, the date and time are what they should be.

First, when I googled the symptoms, the cause seemed easy: just replace the internal CR2032 battery. After all, it's 14 years old. I did that and it didn't help. It did change the volume of the startup chime though, it's much louder now.

Then I reset the NVRAM/PRAM, with the four button thing when booting. That helped for one boot, but on the second boot, 1st of January 2001.

I booted in Safe mode. Several times resetting NVRAM/PRAM. I checked the system settings, but they are what they have been the last 10 years.

Unfortunately, nothing seems to work. Is there anything else wrong with the machine? Is there some other battery that needs to be replaced?

Sometimes I booted the iMac without the Devolo, and used WiFi. Even when it did not have an internet connection, the time was always what it should be. So the strange IP address should not be the cause of the iMac not knowing the right date/time.

  • I'd try another battery - it does still have classic symptoms of flat battery. At 30 p/¢ it's worth a shot. Note: don't ever buy expensive CR2032s, just buy 'fresh' ones.
    – Tetsujin
    Mar 22 '20 at 16:18
  • 30 cents? More like $4 where I live. I haven't checked the date on it, I just bought it in the store and I had no reason to believe it is an old one. I just hope the store will be open when I have time to visit it, I foresee a closure because of the Corona crisis. I can also check whether the battery is in place properly, maybe it's a bit loose. Mar 23 '20 at 7:09
  • There is typically a plastic insulator on the battery, did you remove it prior to installation? Also is it installed the right way up. Positive should be facing up/out.
    – Allan
    Mar 23 '20 at 11:46
  • @Allan Yes I did, I even have a witness who saw me do it. But I am going to check the position, I am 99% certain that I did it right, but I'll check again. Thanks. Mar 23 '20 at 13:00
  • Don't need a witness, just saying it something to check. Someone recently had me looking to replace a car key fob because it died. Only then did I open it up and find the brand new CR2032 with the sticker still attached.
    – Allan
    Mar 24 '20 at 1:16

Because I had 1% uncertainty about how I had placed the new battery in its holder and because I wanted to make sure it was firmly in place, I reopened the iMac. And what did I behold? The battery holder is supposed to be connected to the motherboard on two places, the upper and bottom side. And the upper side was loose! This must have happened while prying out the old battery, that is an even trickier operation than I thought it was.

So that was the cause. Now I have the challenge of fixing this. Duct tape (to hold the battery holder down on the board) didn't help, I can tell you that by now. It should be soldered, but I have neither the equipment nor the skill to do that :-(

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