Fan goes at high speed, computer pendles two correction pictures

Have just replaced the PRAM battery. Two mistakes during the job. First the optical drive thermal sensor socket came loose in stage 15. second, I discovered I had a CR2032 battery and not a BR2032 but changed the battery anyway.

Tried gluing the socket back to the logic board, which looked as though it was successful.

However, when restarting the machine, the fan starts hissing and there is a noticeable draught from the opening. The machine appears to start to the rotating lines, but instead of booting two pictures start to oscilate.

One shows an oval shape with a rectangle inside. At the top right is another small oval which is the focus of an enlargement and indicates that a switch should be moved up

The other shows an inclined plane with a cylinder at the right, and on the cylinder end is an on-off switch which is indicated by an arrow.

Any ideas welcome. I'm going to open up the computer again and see if there is anything obvious, but I wonder if the loose socket is not sitting perfectly and the fan is trying to cool the optical drive.

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Further note: I have just found out that this CR2032 is not rechargeable, so I will have to replace the one I have put in. :(

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Still another note: I went back in and nudged the optical drive sensor, and the fan activity stopped. Unfortunately the computer will still not boot normally but goes to showing the two pictures alternately.

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High/max speed fans on a Mac are generally the result of a sensor not being able to be read. If the thing came all the way off, it'd need to be soldered back on... assuming that the pads are still intact.

The battery should be fine. CR/BR doesn't look like it matters... I wouldn't worry about replacing it until you need to.

Any way you could post pictures of the images the machines getting?

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Thanks, Shaun:

You can see them at: https://www.facebook.com/james.wilde.642...

I couldn't get them uploaded to this site. Sorry.

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That means it's just not detecting a mouse and keyboard.

The fan might be okay now... hard to say. Typically fans ramp up when the machine is powered on so the board knows everything's okay with them, and then they'll adjust to whatever load needed. When they're at max 24/7, that means a sensor is malfunctioning, though.

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Thanks, Shaun. I'd connected what I thought was the minimum number of connections when testing the mini, and didn't realise that I'd not connected the mouse and keyboard! You've solved my non-starting problem. Now I find that the machine does not locate the internal disk - it's booting from an external disk I had once, which is still connected. So tomorrow I'll check the internal disk connector. I take it the disk gets its power from that connector, too, so it's not that I have not pushed the logic board in hard enough or something?

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Yeah, that connector provides both data and power. It's likely just not nudged in all the way on the hard drive side of things.

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You were right again - it sat a bit loose. Now I've got the fan blowing a gale again, but I can live with that if I can't fix it. Thanks, Shaun, you saved me having to buy a new Mac, and built up my self-confidence when it comes to repairing my Mac. Problems solved.

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Yay, I'm glad you got it sorted. My own electronics repair history is riddled with stupid, silly stuff. I only know how to do micro soldering now because of my own screwups. You'll always make mistakes, but you get faster and better with undoing those mistakes.

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