Oh I'm sure that Ignition switched is fused somewhere. But I wouldn't have a clue at what rating.

I'm going to redo the basic install The Right Way(tm). I've just bought a Monster 10Ga amp kit to handle permanent power and ground for the HU and empeg. I'll have to hack my sled harness around somewhat to cater for it.... Hmm. I need some 10Ga capable quick connects.

After that I'll look at the GPS again. It was a quick and dirty hack in the first place. I know that there's room for improvement there.

try powering it from the 12v permanent feed and/or the 12v ignition feed instead of powering it from the amp remote line

Can't come from permanent. It's a stealth box with no Off switch. I suppose it could come from ignition switched, but I'd then have to fuse it.

You could have it come for permanent through a relay activated by the amp remote line. Maybe.

Yeah, that's probably where I'm headed.

And after pulling my entire dash apart again this afternoon, and buying all the little odds'n'sods needed to redo the whole thing, I notice that the audio ground connection of the Blitzsafe is tentative, to say the least. How I didn't notice this before is beyond me. (Although it's hardly over-engineered). I'm now wondering if all the alternator whine will disappear if I simply correct this, and if I could have saved $30 on parts. Oh well, in for a penny...

Well, fixing the Blitzsafe didn't fix the problem, although it needed to be fixed. I'm sure that having an audio ground hanging by a thread is not a good thing. It was a PITA to get the socket out of the housing in order to resolder it. And then when I was done soldering the socket, I discovered that was not enough slack on the audio signal wires for me to be able to place the ground socket back in the housing, so I had to unsolder it, place the socket halfway in the housing, heatsink it somehow to prevent melting the socket and re-solder it. Way too much fun for my liking.

Anyway, as I said, that didn't fix it. I eventually traced it to being a bad ground connection at the sled connector. I couldn't see anything wrong with the crimp, but for some reason wiggling the wire made a difference. I also discovered that both microphone crimps were bad, and the amp remote line was virtually out of the connector. (I'm sure that didn't help with the GPS noise!)

So I ran a 10ga ground line to the back of the sled using the 4mm threaded hole, and then tapped the existing looms ground into it. That seems to have fixed the alternator whine and empeg noise completely. What (very little) noise remains doesn't appear to be empeg-related - I can also hear it if I play a blank tape. I'm guessing that it's just noise picked up on the 12V line in the loom. When I ran the ground line, I included a beefy 2 position molex connector, so I could easily add a 12V line too. I'm now trying to decide whether to take it from the distribution block behind the driver-side dash, or go the hassle of running it through the firewall straight to the battery. Hmm. Decisions.

Cool, glad you got it fixed.

Where'd you run the 10g ground to?

At the moment is run to an unpainted dash support strut that's bolted into the tranny tunnel. (Yeah, ok, it's a FWD car, but the shift linkage still has a tunnel...). Looking around under the dash, the dash supports are used as ground for other stuff, and I think that's as good as I'm going to get without either running out to the battery or drilling myself a new hole in the floorpan. I'm lucky because the strut has had material removed to lighten it so I've just been able to run a 5/16 bolt straight through it and tighten a nut on the other side.

Yeah, that's the correct place to ground it. The only time you'd want to go to the trouble of running it to your battery is if you'd had trouble with that grounding point.

Is grounding the harness AND the sled a common thing to do?

Ideally, the harness ground and the player casing should be the at the same potential anyway. At least I think that's how it's built, many other car stereos are made that way.