Wire harness meltdown

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Wire harness meltdown

Postby Pmat on Mon May 28, 2018 5:34 am

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My son’s 2007 honda metropolitan scooter suffered a wire harness meltdown behind the fuse block that attaches to the positive battery teminal. At first I thought that mice may have chewed the insulation as this has happened to me before, but could see no evidense of mice. I also noticed that while most of the melted insulation is to the wires directly in back of the fuse block, there is a wire melted bare that runs to the starter relay.

The scooter tag says made in japan but the wire harness is labled as made in china. I’ve ordered a new harness but am concerned that there may be an underlying problem. Scooter was working fine until the meltdown. Ideas?
Pmat
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Posts: 3
Joined: Mon May 28, 2018 5:13 am

Re: Wire harness meltdown

Postby Pmat on Sat Jun 16, 2018 9:34 pm

I've made some progress on fixing this scooter. Installed a new wire harness, but it still blows the main 15 amp fuse instantly when the key is turned on. I am guessing that the wire harness meltdown was caused by someone (not me) tampering with the fuse socket or putting in a much higher amp fuse. I have eliminated various components one at a time but still have not found the short. it may be in the ECM. I discovered that if I remove the starter relay, I can turn the key on without blowing the fuse. then I can kick start it and it runs fine. Having systematically eliminated all components on the starting circuit and not located the short, I'm beginning to look at the likely hood of replacing the ecm.

ideas?
Pmat
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Posts: 3
Joined: Mon May 28, 2018 5:13 am

Re: Wire harness meltdown

Postby Pmat on Thu Jul 05, 2018 4:20 pm

Solved and fixed! It was the ECM, don't know why this took me so long to track down. Perhaps because the Honda service manual that I finally got my hands on has no direct diagnostic procedure for the ECM. It's check this component or that Indirectly pointing out that if this or that test passes then it could be the ECM. Eventually, I just decided to check the ECM side of the starting circuit and noticed that there was continuity between the RED and Green on the ECM side of the 6 pin connector. When I pulled the red wire from the starter relay out of that connector the fuse no longer would blow when I turned on the key and I could kick start it. bought a used ECM on ebay and everything works and is running fine.

A word of advice, I suspected it might have been the diodes in the ecm starting circuit, and thought I might "un-pot" the ECM (remove the epoxy compound that the electronic components are embedded in) and repair the ECM. An exercise in futility! After reading about un-potting electronics I thought I would give it a try. I tried heat, solvents etc. As far as I can tell it's not possible. Eventually I smashed it with hammer and chisel just to see the inner workings. The electronic components are embedded in epoxy or something very hard on both sides of the printed circuit board.

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Pmat
Member
 
Posts: 3
Joined: Mon May 28, 2018 5:13 am


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