Blowing fuses can’t find a short.

[kinger]

My wideband controller doesn’t have power and I thought it would dive into it. 

@halfspec put in a rear 12v power relay that goes from the battery through a relay and then powers my radar, racelogic TC, and my wideband controller.  I put a fuse in and it pops instantly in spectacular fashion.  I can access the relay he hid in the back truck area by the jack.  With the relay unplugged circuit doesn’t pop a fuse.  Plug in relay and it pops.  Bought a new relay and same result. 

I have the Racelogic, wideband, and radar all unplugged so there nothing that should power.  It still pops.  To me that means I got a pinched wire after the relay shorting directly to ground.  Before I pull the car apart and inspect every wire any other ideas?  All wiring is sealed up nice and in loom so a chaffed wire seems like a very low probability on a car with 20k miles since he put it in.  Seems like a waste of time looking for a wire and I will have to pull the bins and I really don’t want to do that. 

I could always rewire the UEGO controller as the wires are all accessible. But the Racelogic and radar are buried. 

Thanks!!


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[Gunnytron]

Could you unplug the high load wires, to test which side of the relay is popping the fuse, the low.or gigh load sides?

[kinger]

Right now nothing the relay powers is plugged in. With out the relay it won’t pop the fuse because it’s an open circuit from the battery where I can access the wire and inline fuse. Plug the relay in and it pops.  Checked the relay and it’s 93 ohms and works as it should.  Tried a new one anyway. Same result. 

So I’m thinking it’s after the relay. 


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[Gunnytron]

Have you tried bypassing the relay? As in don't leave an open circuit when the relay is unplugged?

Bypass the fuse and wait for something to start smoking?

[kinger]

Uffda, I don't think I want to do that LOL  It pops instantly and with a ton of spark.  See the attached pictures.  You can see the harness, I think I will probe the UEGO wideband plug which is also in the battery bin.  See if those show open between power and ground. 

Halfspec elec manual for the win  So nice to reference this a decade later!

[kinger]

Man its nice to buy a car with a FULL updated wiring manual! 

I have been studying that and the X23 connector in the rear close to the spare tire and pass taillight, I figured out @halfspec ran switched power through that connector repurposing pins that he removed from the power antenna.  That clued me into disconnecting that connector it would allow me to test the harness I showed in the above post.  Sure enough I disconnected that and the fuse didn't blow.  So now I know the short is in that other harness going from this location to the Racelogic and Radar power wire. 

The weird part is I expected my Wideband to power up now because I didn't see any connections for that circuit that would run through this connector.  It did NOT, so I will continue to track that down.  I attached that picture and now with the White plug disconnected in the lower right corner (X23) it no longer blows fuses when switched on so those wires and relay should be good. 

Fun stuff!  Couldn't imagine trying to work on a PO wired car without this manual! 

Here is a link to his if anyone is curious, crazy amount of work!!

https://www.halfspec.com/downloads/rx7/Halfspec_FSM.pdf

[Gunnytron]

Good progress.

Top notch build that one.

[kinger]

Found it!  Of course it was my shoddy wiring for the radar lol. I don’t know what I was thinking years ago. Now I’m wiring Motec and I just shake my head at stuffing excess wire into the metal hole that is the dome light access hole. <SMH>

Thanks for listening while I figured it out [emoji1787]


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[MPbdy]

Glad you found it lol I feel your pain.

[kinger]

Glad you found it lol I feel your pain.

I sure am glad as I get older my patience and wrinkled nose are starting to save me a bunch of work.  10 years ago I would have ripped every panel off, pulled the bins, only to find Halfspec wiring in minty shape.  Sometimes when I get stuck I just shut the lights off in the shop and think about stuff away from it.  Come back do 5 mins of diagnostics, and repeat.  Doing this I have 15 mins into diagnosing this vs the HOURS I would have spent before.  Downside is it took a week LOL 

I think I will road trip it tonight down to Des Moines 

[cholmes]

Sometimes when I get stuck I just shut the lights off in the shop and think about stuff away from it.  Come back do 5 mins of diagnostics, and repeat.  Doing this I have 15 mins into diagnosing this vs the HOURS I would have spent before. 

This is me, so much! When I start to get wound up about a problem, just walking away and doing something else, or even taking a long hot shower and getting a good night's sleep makes all the difference.

[digitalsolo]

Learning to do LESS and think more is a hard learned skill. 

[kinger]

Did a 250 mile drive in one evening down to DM from northern Iowa. It was a very pleasant drive, in AC and nice to be in the seat that long in the car.  I think for years it’s done 40 miles to work and back and that’s it. 

Makes me want to redo a bunch of stuff to make it fricken perfection for a street car.

They are fun when running mint!


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