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Blown fuse when ignition is switched on


Abowen
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I have a 2018 Hd5 that won’t crank. Started with no power to dash display and traced it back to a blown ignition switch fuse (F8). I replaced it and it will now stay intact for about 10sec before it blows again. I’ve unplugged the brake lights, fan, and fuel pump and haven't been able to locate any grounded or damaged connections/wiring and it still blows the fuse. When the pump was connected I couldn’t hear it running either. Any ideas of where to search from here?

Edited by Abowen
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The F8 fuse provides power to the ignition switch as a stand alone and the ignition switch turns on the ECM. Check and see if you have power at the ECM while the fuse is still good, the ECM appears to be the only item drawing power through the ignition switch, I hope its not bad. I am not sure how you would test the ECM without taking it to the dealer?

The F4 fuse provides power to the instrument cluster and it appears to get power from the R2 relay. Try switching relays if they are the same and see if anything changes but keep track of the original R2 in case you need to replace it.

There is also a fusible link that provides power to Fuse box 2 under the hood but if you continue to have power at the other fuses it should be fine.

Your machine HD5 may be a bit different: items to check if F8 blows, defective diode D2, defective starter solenoid, or shorted to ground. Good luck.🤔

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