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A1418 / EMC 3068 / iMac 18,1 / 2.3 GHz dual-core i5 processor. Released June 2017.

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No display and no chime.

2017 iMac with display issues and no chime at boot.

1st 3 LED’s light up but the 4th LED will not light up and external display does not work either.

If the cables for the monitor are attached fan moves slowly. If I disconnect the cables and turn it on fan blows at full speed.

Is this a display issue or a logic board issue?

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The fan is likely working correctly here. SMC controls the fan based on thermal sensors, so when you disconnected the display cable SMC went into CPU Safe Mode which will push the fans RPM.

With that said this series uses the integrated Intel graphics engine within the CPU. Sadly that part of the package failed. You need a new logic board.

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Thank you very much for the reply!

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