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Old 01-05-2023, 02:19 AM   #13 (permalink)
JimmyK
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Quote:
Originally Posted by Jhill View Post
Ok so I’m a bit out of practice since I’ve been out of the industry for about 6 or 7 years now but it sounds like your chasing an intermittent short with a fuse that feeds a bunch of parallel circuits. It sounds like it’s at least consistent enough you can get it to blow reliably so that’s a good thing. So what you could do is use a recording dmm or scope with an amp clamp on and you’ll have to monitor each branch of the circuit while the fuse blows to see which one is spiking.

The other option which I’ve had to do for a customer that would blow one fuse every 4-6 months so very intermittent and that fuse fed 5 wires which then each split into 3 other parallel circuits so there was no way I was going to find it. In a situation like that or what you can do since most likely don’t have a way to record amperage is go get a bunch of in line fuse holders and fuses and you’ll have to cut and wire in the in line fuses on every branch that fuse feeds. Once you have the branch with the fuse that pops you’ll have better isolated the components and wiring path you need to inspect (took a while but finally found a hairline crack in a wire that would intermittently touch the window regulator channel).
Hi Jhill, thanks for the reply!

I was thinking of doing a test like that but with cheap DMMs; I was going to put the vehicle on a trailer and have someone drive it around until one of the DMMs shows a short. Your test makes things even easier since the amp clamps are not invasive, so the harnessing can be plugged in and the car can be on. I would probably label the few multimeters that I use and record it with a camera so that I can be sure I don't miss the fuse popping if I do this.

I'm glad that you also mentioned the in-line fuse method because I was thinking of doing that since it's only a few lines coming off the fuse to the parallel circuit, so I could try to isolate things by only popping two or three fuses. I'm worried about cutting the wires and installing those because they're a future failure point, and because I was worried about resistances or impedances being a little off before going into the ECU (I'm less worried about that now though since I know they are all power lines).

Sounds like this is gonna be way harder than it has been regardless.
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