So softtouch...what I'm gathering from all this is that the resistor wiring for the System Sentry/lamp out system seems to also be calibrated with just enough tolerance for LED bulbs as well as the factory incandescent bulbs. Does that sound reasonable?
I did the LED conversion on my own two cars but neither had the System Sentry. If there's a problem then I need to let people know about that on my site. But it sounds like, if all else is working properly, then the LED conversion is still not an issue.
Ahhh, okay, the auto lamp/dim thing makes sense then. Glad you figured that out, that would drive a person nuts LOL.
So with those out of the picture now, you're still getting a 'lamp out' warning light? That person might be on to something...personally I haven't experienced a bad LED bulb but that's entirely possible.
Another thing you can try is swapping in the old incandescent bulbs, one at a time, until the warning light goes out. That should give you an idea of which LED bulb has the weak diode. I've found that, once swapped to LEDs, you can put the old incandescent bulbs back in without penalty to the new LED-spec flasher unit. (You can actually mix bulbs and everything still works just fine).
IIRC the System Sentry is reliant upon all the bulbs being halogen. Otherwise, a non-halogen bulb will cause the System Sentry to go a little haywire just like you're experiencing now. There must be some resistor wire-y stuff going on.
So it seems like you'd need to put some inline resistors in. They're sold primarily for newer cars; older cars like ours technically shouldn't need them but in the case of System Sentry, I'm betting that's going to help, at least with high-priority bulbs like the headlamps and taillamps. For the rest of the car's bulbs, I think there's just too small of a draw to justify any resistors on those circuits. Just my thoughts on this.
It's been a few years for my LED conversion in both cars and they're just fine...then again, I don't have System Sentry in either car. But no issues with the multifunction switch if that helps.
Speaking of, if you resolve the issue with the headlamps and taillamps, your multifunction switch might just prove to be alright. Sounds like you're getting feedback through the switch...which kind of makes sense with the headlight wiring routing.
Sounds typical of the era, I noticed some of that myself but had always been able to get everything aligned well enough. Surprisingly, the switches have always behaved perfectly in my car...up until this moment when I mentioned them. Ah well, it was a good run...
Nice progress Matt! The carpeting/console combo looks fantastic.
Just FYI, I'm not positive but the rear power window motors might be clocked. I replaced one of mine a few years ago (and it turns out that it wasn't necessary, there was a power/wiring issue instead) and it hasn't been exactly right since. I have some adjustments to make right now (in/out), hopefully it doesn't require removing that motor again.
BTW, the new motor was brand new, not a reman, from O'Reillys and I believe it was listed under a 1984-ish Pontiac Bonneville 4-door. It's a little quieter, doesn't sound like C-3PO's body movements anymore*. I kinda miss that sound...but the other side is still the original mid-1980s motor so I've got that.
* Seriously, an old Cadillac window motor was the basis for the sounds of C-3PO's movements in the original Star Wars movie (A New Hope). Subsequent movies had different sounds for him, but The Last Jedi brought back the GM window motor sounds.
If the slimmer Marchal 150's (1988.5-90 Escort GT) would fit in the smaller air ducts on either side of the 1987-88 T-Bird bumper cover, that would be a great option. I think they're still too big though. I've seen just generic aftermarket slim fog lamps in those slots and they look decent, but they aren't Marchals by any stretch.
Nice! Love the cluster nice, looks so much nicer without a gear indicator in there. And I didn't know those quick-disconnect steel lines existed...that's an awesome solution.
BTW, if you are sticking with the stock steering wheel but want one in better shape, let me know. I have a leather wrapped one in that color, really good condition. The 1984 A-frame wheels are unique so I'm always trying to stock up on them when I can.