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Old 03-07-2016, 09:48 AM   #1
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Default Calling any wiring gurus

Hey guys so I have what I think is probably a hard question to answer without seeing the wiring but there may be common issues that I don't know about.
So my miata ('93 with '97 1.8) has trouble getting power. Sometimes it starts just fine and other times I turn the key and there's nothing. No lights, no cranking, nothing. Which means no power. I know absolutely nothing about wiring. I'd love to learn so I guess the first step would be to ask you guys what I should check. I've checked all grounds and they all seem to be fine. The negative battery terminal ground is pretty ugly. The kid who did the swap didn't do the greatest job. That wire is frayed all around the ground but it is grounded so I don't think that would be the issue.
Any help would be appreciated.
Thanks
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Old 03-07-2016, 10:05 AM   #2
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Originally Posted by ryankpeck View Post
So my miata ('93 with '97 1.8) has trouble getting power. Sometimes it starts just fine and other times I turn the key and there's nothing. No lights, no cranking, nothing. Which means no power.
By "nothing," do you mean literally nothing? As is, no headlights, no brake lights, and no horn?

How about the radio, the wipers, and the HVAC blower?

My guess here is that the problem is in the vicinity of the keyswitch. Either the switch itself or the wiring behind it. If the headlights, brake lights and horn work, but nothing else does, then it's almost certainly that switch.
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Old 03-07-2016, 10:14 AM   #3
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replace your battery ground, and make sure the battery itself isnt bad.
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Old 03-07-2016, 10:22 AM   #4
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Pics when you get a chance.
By checking the connection I assume you mean unscrewing that connection, cleaning all associated parts to bear metal; a Dremel with a wire wheel works great for this. Assemble with dielectric grease. Repeat for all grounding points.
The ground from the battery can be upgraded with one of the many fine products we have available. my .02
-JB
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Old 03-07-2016, 10:34 AM   #5
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By no power I mean absolutely nothing. No brake lights, headlights or headunit. The grounds I've taken them all apart and made sure they were down to bare metal with a wire wheel. I haven't used dielectric grease but I can definitely do that.

When I get a chance today I'm going to take a picture of the negative ground because after looking up replacement negative battery wires I'm thinking it may be wrong.

I replaced the ignition switch a while back because it was bad but this is different as I have absolutely nothing happening. It's also a brand new battery so that's not the problem.
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Old 03-07-2016, 10:58 AM   #6
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Hmm...

It could also be the 80A Main fuse, or the connections thereto. It's in the box under the hood, and is secured with screws underneath.
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Old 03-07-2016, 11:18 AM   #7
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Just did this with my car. It was a badly corroded negative terminal on the battery. It sounds like itnmay be something different for yours if you have cleaned that up though.
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Old 03-07-2016, 01:57 PM   #8
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Changed the 80A main fuse yesterday thinking that was it because it was pretty badly corroded but that didn't make a difference unfortunately.
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Old 03-07-2016, 01:58 PM   #9
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Just did this with my car. It was a badly corroded negative terminal on the battery. It sounds like itnmay be something different for yours if you have cleaned that up though.
It was the terminal itself or the ground? I haven't done anything to the terminals
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Old 03-07-2016, 02:02 PM   #10
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the miata already has shitty grounding.

if you have a frayed ground strap your miata isn't going to play nicely.
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Old 03-07-2016, 02:04 PM   #11
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Alright well I guess the negative ground is definitely the first step then! Thanks braineack
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Old 03-08-2016, 12:06 PM   #12
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Remember that all of the +12V comes down the starter cable to the starter and then gets distributed from there. I'd check that connection first before replacing anything.
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Old 03-08-2016, 12:21 PM   #13
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Oh wow ok that's definitely something I haven't checked. Thanks a lot barby
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Old 03-08-2016, 12:23 PM   #14
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Also, looking at that diagram, it shows the negative battery cable just grounds and that's all. Mine goes further than just grounding. I'll have to check to see where it stops next but I know for sure it doesn't just ground and end there.
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Old 03-08-2016, 12:51 PM   #15
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Quote:
Originally Posted by ryankpeck View Post
Also, looking at that diagram, it shows the negative battery cable just grounds and that's all. Mine goes further than just grounding.
It's been a while since I looked at the battery wiring in depth, but I do recall you're right. I'm pretty sure that the battery ground cable continues on from chassis, pops out under the car, and attaches to the PPF.

The other key ground is the obvious one from the engine block to chassis on the exhaust side, but I'm sure you've already verified that.
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Old 03-08-2016, 12:56 PM   #16
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Originally Posted by ryankpeck View Post
Also, looking at that diagram, it shows the negative battery cable just grounds and that's all. Mine goes further than just grounding. I'll have to check to see where it stops next but I know for sure it doesn't just ground and end there.
it showing you where the battery itself grounds (just off the battery in the trunk), but not where everything else does to it.
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Old 03-08-2016, 12:57 PM   #17
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I have checked the engine-chassis ground but I haven't looked at the ppf so I'll check the starter connection and the ppf ground tonight.
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Old 03-12-2016, 06:37 PM   #18
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Alright so I just want to give an update.
Today I changed the starter, battery terminals and fixed up all grounds including dielectric grease.
I'm pretty sure that the starter was the issue but I can't be completely sure since I did so many other things.
Thanks to all you guys for suggesting things to do!
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Old 03-17-2016, 07:41 PM   #19
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replace your battery ground, and make sure the battery itself isnt bad.
Can second this I had this exact problem on mine. Found out that the terminal end of the wire was broken and wasn't clamping to the negative terminal anymore. Replaced it and solved it.
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Old 03-18-2016, 09:47 AM   #20
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The brain didn't even mention the terminal end in his post and if you read the last post the problem has been resolved. Pretty sure it was just a bad starter connection
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