I have been here on the forums for 3 hours trying to find an answer or at least get pointed in the right direction.
The car is an S5 N/A and I have replaced the wiring harness in it. Before you blame my work be sure to read please. I installed the wire harness about 5 months ago
and everything was working, as it was just a shell. I tested headlights, turned the ignition on, coolant buzzer went off, turn signals worked, air blowed from the vents etc.
Now fast forward to last week. I installed the engine and transmission and the only wire I hooked up was the alternator. Today I buy a new battery and put it in the car.
Some how I only have headlights and emergnecy flashers now. Turning the key does nothing at all. The car has no power in ACC or ON except for the headlights.
The headlights will also work with the ignition in the off position as it should.
I checked the engine fuse and it is fine. I also called myself checking the main fuse but I dont know how to tell if it is blown or not.
I put a meter on it and it has battery voltage on both sides so I assumed it was good. Even though I still swapped it with another fuse.
I also swapped the main relay with a working one from my daily driver. After reading on here for a bit I got the idea to bypass the main relay.
When I do this the headlights come on when the car is off and the headlight switch is positioned to off. If I turn the key to ACC or ON like this there is a
burning smell coming from the battery. If I remove the headlight fuse with the main relay still bypassed the car acts normal. No power when the key is off,
power when with ACC and ON. This is as far as I got before it got dark and I stopped.

I was starting to think the ignition switch could be bad, but if that was the case it shouldn't work with the main relay bypassed. Or am I wrong about that?
If the main fuse was bad, the headlights would still work as they are, but I should not be able to get power when bypassing the relay as well.
Could the two wires that connect to the main fuse be reversed? Does it even make a difference? I don't understand how the car can make this big of a change without
me touching the wiring since it was working fine before hand. Could I possibly be using the wrong headlight switch for the headlight issue? Is it possible the headlight
issue could be tied into keeping the car from getting power from the ACC and ON positions? Tomorrow I will make sure I have voltage coming into the ignition switch.

Any help is greatly appreciated. I have been working on this car for over a year, and within a week of cranking another giant set back....

Another thing I don't have internet where the car is so, I will have to take as much info as I can and apply it, then return with results.

Thanks again!!!!

 

The EGI fuse in the engine fuse box is responsible for delivering constant power to the Main Relay. The Main fuse is not responsible for powering the EGI fuse, but is responsible for powering the ignition switch. The lights are powered by the BTN fuse so these lights are independent of the ignition switch and thus the Main fuse.

 

I remember years and years ago, I had the same problem...

There's a small connector in the engine bay near the battery that will cause this to happen if it is unplugged. Look for any unplugged connectors in that area.

 

When turning the key to ACC this bridges the bw wire from the main fuse with the "xxxxx" one from the ACC wire on the ignition switch to the fuse box correct?

 

The constant voltage at the Black wire found at the ignition switch passes voltage on to the Blue wire at the switch which then powers the ACC fuses at the interior fuse box. It is possible in your case that the B/W wire that is powered by the Main fuse has disconnected from the Black wire which powers the ignition switch and this connection is found below the engine fuse box. Also, the Main fuse might have blown. And to clarify something stated earlier, the interior accessory lights and brake lights are powered initially by the BTN fuse while the headlights are powered by the Head fuse.

 

Ok, I the wire that connects to the ignition switch and it was getting extremely low voltage. At 1st I didn't understand why because this is the same wire that is connected to the alternator and at the alternator it gets 12v. Long story short that cable came from a different vehicle and one half off it had come disconnected from the butt connector. After fixing that the ignition switch is now working, but still the main relay is not working I believe. The car is not getting any spark and will not start. If I bypass the the relay the car cranks up and runs for about 4 seconds then it turns off. Im sure that may be a different issue all together but next is to look at that main relay. I won't have a chance to next week, so this is my update for now.

Thanks for the help.!!!

 

I had THIS same issue (it was BADLY corroded, but still connected) when I first got to college before I knew ANYTHING about cars... my stomach was in knots over this. Ari helped me out over the phone - couldn't believe it!

 

Check the 15 amp Engine fuse as it's supposed to provide voltage to the relay's coil w/key to on. The relay has two plugs and the B/W wire in the two wire plug is the one powered by the Engine fuse w/key to on. So check that particular wire w/key to on and if it doesn't have voltage then it's likely the fuse and if it does by chance have voltage w/key to on then make sure the other wire in the two wire plug is grounded properly for if it isn't then the relay coil will not work as supposed to and the relay will not work as designed.

 

That 15 amp fuse is not blown and I changed it out anyway with no results. I did not check the voltage from that two plug wire. How do I make sure that the other wire on it is grounded? It goes into the wiring harness and have no idea where it comes out at. If it ends up being the relay not having power or ground to click over, what would typically cause that?

 

Not sure where the ground wire leads to on an S5, but on an S4 it leads to a plug located under and to the side of the trailing coil up against the fender. W/o the ground and or voltage on the B/W wire the relay will not work. If you removed the relay and laid it down on the battery and provided voltage to one of the terminals in the two wire plug connection spot and an intermttent ground to the other terminal than the relay should click.

 

I'm betting its the pure black wire that feeds the ignition switch like already mentioned in two posts above.

That black wire that feeds the ignition switch has a single black wire connector near and inboard of the engine bay fuse box. LOOK for it.

That wire is also spliced to the large wire that feeds the alternator. Just because the alt output wire has batt voltage does not mean the small 18ga black wire that feeds the igniton switch has power. LOOK for that single wire black connector with in three inches of the engine bay fuse box and check it for power and being connected together or in a worse case.......fried beyond all recognition because someone connected the battery up *** backwards.

 

Hailers, that was the issue to my problem with the switch. The wire was not
disconnected in the place you specified but the basically cut in hlaf in the middle.
After fixing that the switch works perfectly and the car works as it didnt before. Everything minus what the main relay controls. If I bypass this it works. The issue you mention is fixed and made a major difference so I think it is also related to this one. That two wire plug on the main relay may not be getting ground or voltage. That is my next step it seems. Im really thankful for everyones help!!!

 

Words removed for , well being wrong.


EDIT: I looked at the series five wiring and the gnd for the main relay for a series five is labled 1. It's unclear to me where gnd 1 is on the series five. The diagram leads me to think it's inside the car behind the gauge cluster.............like I say, not that clear to me.

 

Is the factory alarm bypassed or what about the two fusses in cabin that can be reset. I had the Same problem with my s4 not to long ago it was the single black wire from main fuse block it was connected but wasn't making good connection

 

Quick update. Its been freezing outside and havent had the chance to work on the car until today. So, I go out there and in stead of troubleshooting anything I just take the two wire plug on the main relay and cut the ground wire. Then I supply it to a good ground and the relay is now functioning correctly. So now the only issue I have is the car will not stay running longer than two secs. I had a friend spray starter fluid into the AFM when it cranked up and it kept running. This lead me to believe that it maybe bad gas. So I siphoned all the old gas out and put new gas in. It started quicker but still turned off after two seconds. I swapped the fuel lines around and then it wouldn't even start anymore. Swapped them back and it cranks again but only for two secs. I swapped to another working ecu and the same issue is there. It seems that it is a problem with fuel but I cant seem to pin point anything. Fuel pressure build but im not 100% sure if it is holding that pressure or even if it is the correct pressure. At least now i'm on the right track and the wiring nightmare is over.

Thanks!!!

 

Jumper the fuel check connector before starting the car. There is a fuel switch inside the AFM. Its role is to pass a ground signal to the Circuit Opening Relay when the car starts and the rpm climbs to over 500. The relay needs this ground signal to keep power to the fuel pump. The jumper forces a ground to the relay incase the AFM is not doing the job as it should. And you also might have a large vacuum leak which would cause the engine to die out rather quickly.