Electrical issue (no lights, etc.)
 

Hi everyone, I just picked up a 1992 FD RX-7 and while driving it home I got a heat lamp on my dash. Engine temps and oil pressure and everything were all fine for the last couple hundred miles so I thought maybe it was just the catalytic converter overheating. About a minute later the car and all of the electronics suddenly shut down. If I jump it it seems to crank (won't start), but even with another car's battery connected the only light I can see on the interior is the small orange light where you choose between if you want the AC to recirculate air or not. Everything else stays off.

I've looked through this thread (https://www.rx7club.com/2nd-generati...-power-901009/) and it seems like maybe I've lost power to the ignition switch. I hit some bumpy roads on the drive I was on so maybe something came loose. Any idea what else I should be checking for? I've looked at the grounds and the wiring and I don't see anything loose and all of the fuses in both fuse boxes by the battery seem fine.


[Obligatory photo of the auspicious start]
https://cimg5.ibsrv.net/gimg/www.rx7...682a82eacc.jpg

I think the Japanese cars have a sensor in the cat for the exhaust overheat light, it may have actually got hot or it could have been an electrical quirk, hard to say.

Impossible to say what the problem is, you're going to have to sort through the electrical system. Check for blown fuses, bad connections, sloppy aftermarket electronics, etc.

Dale

I agree with Dale, check fuses first since they are easy to look and see if they are popped or working. If all the fuses check out (both engine bay and inside the cabin), it's time to get a multimeter and spend a few hours on youtube learning how to use it. Generic car channels like EricTheCarGuy and ScannerDanner that would be a great place to start. The driving experience of an RX7 might outshine most other cars from the 1990s, but the electrical system is pretty standard. That's good because you can take advantage of the troubleshooting advice people might post for dime-a-dozen cars like a Ford Taurus or Honda Accord.


There are a few things on the car that should still work with the ignition key off. For instance, the headlights up/down button (on the left side of the dash for US cars) will work with the key off. The wiring diagram shows the headlights should work without the ignition key also, and they don't appear to have any fuses shared with other electrical systems like the dashboard or EFI. If your headlights don't work either, check the connection between the battery and the small fusebox in the engine bay.

Ok, just put the recharged battery back in and the headlights flip up and work work. Windows still don't. I forgot about the fuse box in the cabin so I'll check that. And if not there, it looks like a small wire near the engine fuse box that could've gotten loose and caused this. Will check that and be back in a few.

Fixed it! I blew the main 120A fuse. Got a $3 replacement at autozone and it's as good as new.

Only time i've ever blown that fuse was shorting out the alternator 12v post to ground. I'd be curious why it blew cause thats a big fuse to just go while driving. Maybe take a good look for any chafed or damaged insulation on the main power wiring. Actually now that i think about it, check the wiring to the starter also, if the cat really was badly overheated and you kept going it could have melted the starter wiring but its pretty far away.

I think what probably caused it was that the positive terminal was a little loose, so if I hit a large bump in the road it'd lose electrical power for a brief second from the battery. I'm guessing that caused it to blow. Now that it drives I'll take it to a mechanic and see about some of the things wrong with it. I'm guessing the cat is clogged and overheating on long drives so I'll need to check that out along with some other stuff.