Hello everyone, especially Yamae - I hope he is reading this, you'll see why soon.
Anyway, my 1990 LS is still a pleasure to own and drive. But one thing has been bugging me over time, and I don't want to ignore it any more. Electrical gremlins which I have not been able to resolve at all. Here they are with approximate year they occurred:

2014 - After replacing the A/C LCD display successfully (so I can have a working clock), the backlighting of all the HVAC buttons was not working any more. Opened the entire panel again to check if everything was connected properly and plugged in, and it was. That was the only electrical thing that was not working at the time. To this day, it still doesn't work, which can be bothersome at night.

2014 - installed a double DIN stereo with navigation and rear camera. Installed the GPS antenna under the dash, with strong magnet holding it permanently stuck to some metal bar that runs the entire width of the dash. Also have a rear camera in the license plate frame. The camera works, but the wiring broke so now it is dead until I gather patience to fix that. Stereo and nav work like a charm to this day. (Obviously, I had to pull out the OEM Lexus head unit, and later I pulled out the CD changer from the trunk too)

2018 - installed my own remote lock system. It is a 12v system unlike Lexus's 5v, so I had to tap the wires in the driver's side footwell. The system worked fine the moment I was done, and it still works perfectly to this day. I don't think this would have anything to do with my electrical troubles, especially since they have been popping up randomly over time.

2018 - Rear left door remote lock doesn't work at all, I have to lock or unlock that door manually, while others work fine with the remote control. I thought it was the motor in the door, but now I think it is just another contact or something similar.

2019 - Rear defroster stopped working out of the blue. I want to replace one of the three (or maybe should replace all three?) RELAYS. Checked the connector under the rear shelf and it is connected well. Didn't try to clean the connectors with Electric contact cleaner (CRC) however - maybe should do that?

2019 - Driver side door window button stopped working. Opened it up and cleaned it and adjusted the contacts and now it works. That's the only electrical problem I have managed to fix!

2021 - Cigarette lighters, front and back, stopped working while my son was using a portable tire inflator that was plugged into it. Replaced the fuse, twice, and since nothing else stopped working at the same time, I don't think this had anything to do with any of the relays or other fuses. I should probably try to clean the contacts of the 15A fuse and I am not in love with that middle relay that is in the driver's side footwell, so I will replace that, but what if that's not it?

2021 - Remote mirrors stopped working - can't adjust them with the remote button inside the cabin.

2025 - Shifter stopped working - I have to press the "unlock" button to move it out of park. The rear lights, including stop lights, work fine however. Didn't check the little switch at the brake pedal as I still have the old, OEM one there. I kinda doubt that's it, but it could be. Anyone had their OEM brake pedal switch go bad on LS?

All interior lights work, all the switches work, windows, door locks, etc (Except for remote mirrors and rear left door lock), all the door lights, exterior lights, trunk light even glove box light - they all work. I don't know if my model is supposed to have heaters inside exterior mirrors, but if so, I don't think those work.

Oh, and if it makes any difference, I live in N. California - rain in winter, warm summers, and salty air all around.

Currently, I am most interested in fixing the lighters and rear defroster. Is there a wiring loom that would explain all this? Or maybe contacts wearing out over time?

 

The video below may help you to fix the cigar lighter issue. There is a thermal fuse behind the lighter.
Regarding the defroster, I happened to have a wiring diagram attached. Hope this may help you to troubleshoot.

 

Thank you Yamae! As for the lighter, I saw that video a while ago, and then remembered that both lighters stopped working at the same time. The small, built-in fuse inside the lighter itself would only prevent that one lighter from working, right? In that case, the problem is somewhere further away from both lighters...
I am thinking I should clean all contacts first, and go from there.