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No electrical power all the sudden

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Old Sep 15, 2016 | 10:34 AM
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Default No electrical power all the sudden

I'm in the process of a swap (2001 Z28 to 2000 Z28). The PCM is getting tuned, so it's not with the car right now.
I got the motor/trans in and just wanted to check out what the cluster shows and condition of radio/speakers. I hooked up the battery and everything checked out. Windows work, radio works, cluster works, etc.


Then I decided to plug in the harnesses under the right side of the dash, hook up the starter and alternator and splice in the right fender harnesses (they were cut when I bought the roller). After hooking and splicing harnesses, starter and alternator I now get zero electrical power when I turn the key (yes, battery is hooked up and terminals are clean).
I thought maybe the brand new battery drained somehow so I hooked up a known charged battery... same thing, no power.


Anyone have input? Where did I go wrong? Will hooking up the PCM now that all harnesses are connected help? That doesn't make sense to me.
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Old Sep 16, 2016 | 07:19 AM
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This is still toward the top, but here's a bump with a concern...
I'm picking up the PCM today and I'm itching to attempt to start it since I've been without the car since mid-May. My concern... is plugging in the PCM risky due to loss of electrical power? I don't want to fry it if it gets a surge. Should I get power to the car/components before plugging in the PCM?
It baffles me why I lost power in the first place.
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Old Sep 16, 2016 | 07:52 AM
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Just to confirm, you had power to the windows, radio and cluster until you hooked up the 1) starter 2) alternator and 3) wire harness.

I'd start by going backwards from what you've done since it last worked. In order of what's easier maybe. Or what's more complicated. So I'd pull the harness first then the alternator then the starter.

Actually, what I'd personally do is before pulling anything out check the voltage on the battery while everything is hooked up with the key in the off and then accessory position. Then check the current draw the same way. Basically checking if it's something more basic like a short (wrong connection somewhere, pinched wire) or an open (fuse, bad wire etc).
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Old Sep 16, 2016 | 08:09 AM
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Thanks. You are correct. Everything worked until I did the "final hook up"
This evening I planned on doing what you stated: start backwards. I forgot about testing circuits before unplugging everything though.

Before doing the "final hook up" when I would connect the battery I could hear a clicking coming from the firewall area, then everything worked properly. After doing the "final hook up" I don't hear any clicking when connecting the battery.
I absolutely hate electrical issues.
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Old Sep 16, 2016 | 04:40 PM
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Sounds like a relay used to activate. Like I said, either your connections are shorting somewhere, shunting energy from everything and killing your battery (though you'd likely get a good spark and smoke show if it were that bad) or something opened up in your wiring. I'd be very surprised if your harness did this but, hey, weirder things happen.
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Old Sep 23, 2016 | 08:39 PM
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Case is closed. I feel like a moron. The pos cable to the accy post by the fuses was loose.
Now just need to get fuel pressure...
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Old Oct 5, 2016 | 09:42 AM
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Fuel pressure fixed. Actually, I had the fuel pump relay wire from the PCM hooked up to the AC compressor lead. Car is running now.
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