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The main contactor pulls in then drops out again and then the controller shows a contactor did not close (Contactor DNC) fault. What is wrong?

April 26, 2017contactor controller DNC Drops fault main pulls shows wrong

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The main contactor pulls in then drops out again and then the controller shows a contactor did not close (Contactor DNC) fault. What is wrong?

1 Answer

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As part of the controller initialization routine the voltage on the B+ supply to the controller is tested to ensure that the contactor is not welded and to ensure the contactor has closed. If the voltage does not rise to a preset level within a certain time then the contactor is released. The cause is likely to be very low battery voltage or contaminated or damaged contactor tips. Never force a main contactor closed as this may lead to controller damage and personal injury.