No lights, no Crank, DEAD After Headlight Switch Replacement

[gtivalencia34]

I attempted to change the headlight switch and accidentally caused a wire problem that turned off the entire car. I found a broken 8A fuse in the fuse box, I think it is number 9, I replaced it, but the car is still not working. The battery is fine, and I also checked the relays inside the fuse box, which are all not functioning. When I try to start the car, nothing happens at all. Can you anyone explain what happend ? And what is the solution? Replace all relays ? or certain realys.

[Mike W.]

Dollars to doughnuts it's the battery terminals/cables. I don't care what they look like, remove them, clean them and the battery cables, including the little red one that comes off the positive, then reinstall. I don't care how clean they look, you can't see resistance, it's electrical.

And no, do not replace the relays. Off the top of my head, some of the relays are, headlight low beam, headlight high beam, horn, fan stage 1, fan stage 2, main relay, which could prevent starting if bad, but not cranking, nothing to do with cranking.

[gtivalencia34]

I really hope so. I will do that today.

[gtivalencia34]

Nope that did not work. All relays are fried. I will replace the relays first if no go then the ecu.

[Mike W.]

None of those relays, nor the ECU affect cranking. Running yes, cranking, no. Look at the ignition switch next. Why do you say the relays are fried? And how would they all fail at once?

[gtivalencia34]

Mike, i apologize, so I did what you said and it didnt work at first, then I removed all relays to test them and got busy for few hours when I came back to resume working on the car, everything is back on but since the fuel relay is off the car won't start....so I was really happy for that. Btw all of the relays are bad as I tested them with the relay tester so I guess i have to replace all of them which are ridiculous to find.

[Mike W.]

No, all your relays did not fail. I don't know how you're testing them, but I doubt with a meter across the coil and contacts. I've got over half a million miles on BMW from E3 thru E39 and had 2 relays fail, a main on an E28 and a aux fan on an E36.

Now, this is critical. The main relay is special. It looks almost the same, but it's 5 pins, but it's different than other 5 pin relays. If that exact correct relay isn't in the exact correct spot, the car will not start. There's at least 3 different and not interchangeable relays in the fusebox that have to be in the right spot. My guess is you got them mixed up as they're so similar.

[gtivalencia34]

Will investigate tomorrow morning. Thx a lot.

[Mdreamer]

What was the end result of this situation? If the car has been repaired, what steps were taken to get it running again?