1G Testing and Diagnosing a 4G63 Electrical System

[CrackedDSM]

Hey guys, pretty broad thread title for a pretty broad question here. I figured it was a good subject though for beginners and people who don't really know. Like me.

The Question: How is the best way to test our electrical system and/or charging system? My car will outright die if I turn both cooling fans on when trying to idle, and if just one fan kicks on the idle struggles noticeably. The weird thing, is it charges at 14 volts at idle, and under WOT it never drops below 13.8. From what I can see, voltage to the ECU isn't an issue at all.

Is it a wiring problem? Is this normal operation? Should it NOT struggle this hard? If it's not supposed to struggle...where would I start with diagnosing? It's a brand new Alternator, battery is about a year old but was bought brand new. I did have a wire from the alternator cut itself on the metal fan shroud and catch fire a tiny bit, but I've repaired that and soldered it.
Please, electrical and charging system gurus...teach me and by extension all the people who will come after me. Share your wisdom, por favor!


Edit - Car in question is my 91 Talon TSI AWD. Mod list in build thread profile.

 

[luv2rallye]

Depends on whether it's the 4g63 or 420A, and whether you moved the battery to the trunk, and what extra electrical loads you've added.

 

[CrackedDSM]

Depends on whether it's the 4g63 or 420A, and whether you moved the battery to the trunk, and what extra electrical loads you've added.

4G63, battery is in stock location using OEM harness/wiring. No extra electrical loads. No functioning stereo, etc. Headlights are Halogen/non-LEDs.

 

[luv2rallye]

Sorry I just noticed it is a 1g. Where does your alt's yellow wire (sense wire) attach to? It should go to the sub fusible link 4's 30 amp fuse (engine fusebox). Check that fuse to make sure it's good (remove and check with ohmmeter - not just look at it). If good, plug it back in, disconnect battery and check continuity of that yellow wire from the alt to that fuse and then to battery positive. If no continuity, that is your problem. The alt is designed to output whatever voltage is necessary to keep that sense wire at 14.4 volts. So it must go to that spot and be the ONLY wire that goes all the way there (so no voltage drops on it) or the system won't work properly (that's why it is a voltage sense wire for the alt).

 

[TerminalTalon]

It sounds like the regulator ain’t regulating with loads, that fuse is blown or the fans draw too many amps.

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