Jehannum

I don't have to worry about it anymore. My setup will work just fine with a jump now.

The guy who jumped me couldn't stick around, so I didn't really have that many options. I did learn something, though: that the kill switch can't be counted on to fail safe when you overload it

The "not right with this" was the fact that the battery was completely drained, so the alternator was running at capacity for a period of time sufficient to overload the switch.

Did you miss the SPST relay in front of the 1N5402? Because it's like 4x as big in the diagram. And I think it is relevant to location, because there aren't any kill switches with alternator included that will handle more than 20A. I looked.

I balked some years ago at the cost of replacing the stamped metal tray for my battery and instead put a container in for moving it to the hatch. In doing so, I became subject to a number of rules regarding how the car must be prepared to run on the track, the most onerous of which is a kill switch on "the rear-most part" of the car. For reference, here's the ever-popular internally regulated 60/70A Hitachi from a 280ZX: I've had a Moroso 74102 for some time acting as a kill switch (mounted to the rear panel, through the license plate), installed per the directions but I'm getting ready to run a 100A alternator (to support some other modifications), and realized that I'd been dangerously wrong on the install for some time. See, the 74102 is limited to 20A charging capacity, which runs afoul of even the most modest of 240Z alternators' peak output (I say peak, because certainly they aren't running at their rated output, when the battery is charged). I noticed this when I melted my first 74102 after getting a jump on a dead battery (the 10 gauge wire running back certainly got hot as well). So, after rethinking my options, I decided to go with the Longacre instructions (below) and use the switch to kill the field wire. This works fine, if you've got a race car, and you use the kill switch to shut the car down. Otherwise, it'll run the battery dead overnight. After rethinking my options again, I happened on a simple diagram that helped me out. Basically, the field wire should only receive ignition switched power. The problem, then, is figuring out how to get ignition switched power that won't also get fed by the alternator. So I kept the leg of the Moroso 74102 that their instructions intended for charging the battery, but used it as the source for a relay that is triggered by the ignition switch, like so (though adding the 1N5402 relay to keep the car from running on after the key is turned off): Now, you can run a (fused) wire from the alternator to the starter post at whatever you think is a safe gauge, which hopefully already has a big 2 gauge cable running to the back (either with its own breaker, or relying on the switch to melt-safe). I went with 4 gauge, and an inline 100A fuse (though not visible): I'll be switching to a GM 3-wire alternator soon, but this wiring should support the new one just fine.

I'm pretty sure that the + on the coil isn't receiving any voltage on key to "start" when cold. I'm going to troubleshoot that.

The new belt seems to have answered the mail. However, now it won't start when the car's warm, in the cold (<40°F). If the car's cold, it'll start regardless of the temperature. It'll start just fine from a roll, though. Think I'm going to pin my engine harness up, denude it, and see what I can safely strip out (+/hi/lo for RH headlight can pretty surely go away with my relay harness), what I need to replace, and what's buggered.

We'll see how it all goes. I replaced the belt, as the original was almost at the end of its adjustment range. By eyeball, everything looks OK to me.

I followed the rebuild guide from How To Modify Your Nissan/Datsun Engine book, which told me to not bother putting the oil slinger back in when rebuilding. I wasn't actually rebuilding (just replacing the crank damper after my last one delaminated), and then a couple nights ago, I threw my fan belt. Are these instances related? Is the elimination of that one shim just enough to screw up pulley alignment?

I'm happy to help people, but I doubt I'd sell anything. Thanks!

First try. I'm pretty pleased. In deference to the fact that I bought the amplifier off a Canadian, I had to play Rush as its first song. At any rate, the switch hands off control perfectly. When the radio's on, it plays AM, when the radio's off and the car's on, it plays over bluetooth.

An aluminum plate sandwich with 3.5mm standoffs to mate the amp's heat spreader to the sheet seemed pretty ideal, honestly.

And from the "inviting the stereotype" department, this is straight out of the service manual for the Hitachi radio.

I smoke tested the radio after the modification, and it puts the antenna up just fine, and makes AM radio noises when its on, so I didn't screw it up

Final packaging. I changed the scheme because I realized that the amp/bt combo would be on whenever the radio's off, including when the car's off, so I added a 4th relay to switch power to the whole shebang. Mounting location, after pulling all the wires through, and testfitting the amp itself. The antenna harness now carries the radio switched and ignition switched triggers to the back of the car. In doing so, I can now run a modern antenna without modification. Blue wire is the traditional blue wire - switched on when the radio's on. It's attached where the power switch attaches to the main board. There was a 4th hole for passing cable through on the radio, so I didn't even have to modify the case.