99 7.4l blows ECM1 fuse at random

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TYF Newbie
Dec 18, 2022
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I inherited this truck from my father, Ive had a couple other suburbans before but none with the 7.4l. this one has a western plow and runs great (for the most part) until it randomly blows the ECM1 fuse under the hood. After it blows, I would replace it and the truck would start right back up and run fine. I eventually bumped up the fuse amperage and now I l have replaced it with a U shaped wire connector and hope it hasnt damaged something else as a result..... Any ideas as to why this fuse wouls blow in the first place? Ive replaced all battery cables with 1 gauge cable for both batteries and cleaned and dielectric greased all contacts in starting and charging system. Any help is greatly appreciated.

OR VietVet

Multnomah Falls
Supporting Member
Oct 8, 2014
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Willamette Valley
First, welcome to the forum.

Second, A short to ground is the typical cause of a blown fuse problem like you describe. Like @exp500 said, check all related ground points, check ANY wiring that controls anything to do with the plow and you did not say whether the fuse blows when using plow, just driving or both. Replacing with that wire can eventually cause a drastic failure thru the circuit because the fuse is a protection device and the wire is not. I would trace all wires out of the box the ECM1 fuse mounts in and I would bet you have a wire rubbing thru the insulation and grounding to metal and that happens typically from vibrations. Does the fuse blowing happen just when driving forward, shifting to reverse, accelerating, decelerating, turning left, turning right or applying brakes? Check the engine throw in gear looking for motor mount problems and don't forget to check for transmission mount(s) problems.

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