The iMac G5, powered by the PowerPC G5 processor, was originally released in 2004.

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My G5 iMac sometimes shuts down after minutes or seconds?

My G5 iMac (A40338) shuts down sometimes, just goes blank/dark. When it happens its from a few seconds to several minutes after powering up. Seems to have happened on our hottest days (circa 100F recently) though still 80F inside. I vacuumed out and used can of compressed air on the fans and whole board, but saw no obvious dirt to remove. I have thermal compound remover and replacement but don't know where the heat sinks are. I see no bulging capacitors on the board, or anything obvious astray. Am I on the right track?

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Run a third party fan app to check temperaturs... what are the LED diagnostic showing before/at shut down?


machead3 -- Just to expose my ignorance - where do I find a third party fan app? I don't find anything relevant in the Apple App Store, nor a way to search apps by function/purpose. I have vacuumed out the fans and blew them out with compressed air; didn't see any obvious dirt.

When I have had the back off, and started up, the three diagnostic led's come on normally. I have it on, face down, with the back off now, waiting to see if it will shut itself down and make the red heat failure led come on. When it has shut down it was back on, standing up -- can't see the led's. -- Thanks


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Here are some I have no preference or favorite. Some here favor iStat Pro, FanControl orTemperature Monitor

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After all the suggestions from the problem stories I posted, I just finished installing a replacement power supply. Prior to this, back off, face down, three LED's came on normally, it just down shortly after starting up. After replacing the power supply, first trial startup, power light came on steady, no screen display. Second try nothing came on. Third and all subsequent startup tries machine fans came on, no power light, and after a few minutes the one fan, open to the back, sped up and made much more noise. Looking at the 3 LED'S, the first is on when power is available; the second comes on shortly after starting, before the fan speeds up. The third LED never comes on. I have checked for tightness of the main power supply connector, and the connector for the ambient light sensor, which was particularly hard to reinstall. Both connectors appear to be seated correctly, and squarely.

Any suggestions appreciated. -- Thanks


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david G will be eternally grateful.
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