skillzilla

iTrader: (1)

Ok so I let my car sit for a year hoping it would fix itself, no dice! Looking for ANY help anyone can provide, I am at wits end with this junk. Latest diagnostics below.

Car is an S5 TII.

So, Im driving down the road and all of the sudden all my idiot lights go on all at once. My car feels like ti wants to die, and I have to keep on the gas or else it would have stalled. I get to where Im going and let it die. I immediately try to start it up again and dont get anything at all, no gauge movement, no starter, etc.

BUT, I still have headlights, auto seatbelts, cluster lights, hazards, etc. Basically everything that is run off constant power.

I get the car towed home and start digging into it. I start tracing power from the battery through the fuse box under the hood and to the relays, then to the key switch. This is where things get weird.

So:

- I test the 12v power supply to the key switch, and that is good to go.

- I turn the key to ACC, test it again, still have 12v supply AND have 12v on one of the other pins (expected)

- Turn the key to ON and the power supply drops to .2v . No other pins show power, it is basically dead.

I got another key cylinder from the junkyard and test it out, same issue. So, here I am at a loss. I know I have 12v power to the key cylinder, until I turn the key ON then that goes away. Im wondering if there is anything that could put such a huge drain on the elec. system that it would draw all the power from the battery away from the key switch as soon as it gets power. Could a bad relay do this? I tried a relay from another car and it didnt fix it, but it was a used relay so I guess you never know.

What really has me confused is the idiot lights all going on at once when it first happened. I know this happens sometimes for a few different reasons (all bad) but I cant find where I read that a year ago and think I checked everything that would cause it.

Like I said, ANY help would be a huge help, really. Any ideas at all, let me know. I am so ready to have this thing back on the road, its winter time already and I missed the entire summer of fun car times

Thanks in advance!

satch

iTrader: (1)

The voltage from the battery runs to the engine fuse box and from there to the ignition switch so there aren't any relays on the way. It could be that the Main Relay is incorrectly grounding out and backfeeding this ground to the interior fuse box and then back to the ignition switch when the key is turned to the on position. This just a possibility. If you disconnected the two wire plug to the Main relay and then turn the key to on and see if it drops to see if this is indeed the cause or not.

When the idiot lights turn on it is a sign that the alternator is problematic. Disconnect the plug/Wires to the alternator and see if this changes the voltage at the ignition switch w/key to on.

Getting back to the wiring from the engine fuse box to the ignition switch there is an intermediate connector about a foot below the fuse box which mates the wire coming from the 100 amp Main fuse to the wire that runs to the ignition switch. If this connection is poor then it could cause your problem. I would check this connection first.

And are you sure the battery is in proper condition.

If none of these things help then you might want to depin the Black/White wire at the ignition switch that is found in the same plug as the solid Black wire and see if this changes things.

EDIT: Instead of depinning the B/W wire just disconnect the two wire plug housing the Black wire and the B/W wire at the Ignition switch and then jumper a wire from the Black wire in one plug to the Black wire in the other plug and this will take the B/W wire out of the equation.

skillzilla

iTrader: (1)

Wow, in one post you suggested like 5 things I would have never thought of. Thanks man I'll see what happens after trying what you suggested and hopefully report back with some success!

satch

iTrader: (1)

In reviewing the advice given you should check the connector below the Engine fuse box as previously stated first. Then you could remove the 15 amp Engine fuse in the Interior fuse box. The Black wire at the Ignition switch has constant power and w/key to on it powers the B/W wire in the Ignition switch. This B/W wire then powers the Engine fuse which powers the Main relay so pulling the fuse is basically the same thing as disconnecting the two wire plug at the Main relay.

You could also pull the 10 amp Antenna fuse in the same fuse box as it is powered by the same B/W wire that comes from the Ignition switch. The Antenna fuse powered by the B/W wire ends up powering the antenna plus the Circuit Opening relay w/key to on.

And as luck will have it the B/W wire also powers the 10 amp Meter fuse so this fuse would also need to be pulled in case the other fuse pulling and what not didn't help solve your problem. And you could also throw in the damn 15 amp Turn fuse also powered by the B/W wire and the 30 amp Power Window fuse.

I'm more familiar w/S4's so in looking over the S5 wiring diagram has helped to shed light on these other fuses which differs greatly when compared to the S4.

So if the connector below the Engine fuse box is good then disconnecting the two wire plug at the Ignition switch and jumpering the two solid Black wires and turning the key to on allows the voltage to stay at 12 volts you would then start to disconnect the fuses powered by the B/W wire. Of course you will need to replug in the disconnected two wire Ignition switch connector first then followed by the pulling of the fuses to see if the voltage drop disappears. And if this all has no affect then there are other things to look at such as the circuits powered by the Black/Red Ignition switch wire which also provides power w/key to on.

skillzilla

iTrader: (1)

OK, so basically its a matter of taking relays out of the equation by pulling interior fuses that get power from the main fuse by way of the key cylinder to see if isolating a relay from the system causes the ignition switch to retain power in the ON position. Then, if one of these does change the behavior of the ignition switch, look into what is causing that relay to short out/not switch/fail to ground. Makes sense,, thanks again man!!

satch

iTrader: (1)

You should focus 99% of your effort on the connector below the Engine fuse box in addition to the wire that comes out of the Main fuse that feeds the connector just below this fuse box as this is the most likely cause. After doing that and you find the voltage drop is still evident then you should then disconnect the two wire plug housing the Black wire and the Black/White wire at the ignition switch and jumper just the Black wire and turn the key to on and see if the voltage drop still occurs. If it does then disconnect another two wire plug at the Ignition switch which houses a Black/Red wire and the Blue wire and use no jumper wire on this specific plug. The B/R wire powers some fuses w/key to on so you want to prove this wire also is not shorting out. As far as pulling the various fuses, the fuses themselves "should" blow if there was a ground signal backfeeding them so the chance is very, very, very low chance that the problem is being caused by this aspect, but if all else fails then you would go ahead and start removing fuses just to eliminate some various circuits.

skillzilla

iTrader: (1)

Ahhh OK, thanks for clarifying man.

As far as grounds go, are there any that go bad/get corroded commonly that I should check? The one near the brake master cylinder comes to mind, if I recall correctly it provides ground for the main relay. What about grounds on the starter, or from the alternator? I was kind of thinking the issue might be on the starting/charging circuit since that entire loom gets power only in the ON position.

satch

iTrader: (1)

As the negative cable comes off the battery it drops down along the side of the driver's side fender and is bolted to the fender, It then proceeds onward to the starter. This could be a possible cause for your problem but you claim that the circuits powered w/constant voltage are okay and this is primarily because the interior fuse box is somewhat powered by the BTN fuse in the Engine fuse box that supplies the constant powered interior fuses and it uses its own wire to connect the Engine fuse box to the Interior fuse box w/o going through the ignition. This is why the likely culprit is a bad connection of the wire coming out of the Main fuse or the connection below the Engine fuse box that transmits this voltage to the Ignition switch. So the voltage supplying constant voltage to some of the interior fuses is independent of the constant voltage supplied to the Ignition.

The ground for the Main relay should not be a likely candidate for your problem as it occurs "after" the Ignition switch and not before. It's best to focus on the before stuff first and if all else fails then look over the after stuff.

skillzilla

iTrader: (1)

You, sir, have saved my bacon.

This connection definitely had issues, my oil filter is relocated near it and when I changed my filter the last time some oil must have gotten inside the plug, so much so that I couldnt pull the plug apart to test the voltage inside. I tested voltage by probing the wire on one side and it had good 12v, tested the other side and boom, .2v! I bypassed the plug to test it out and sure enough, ignition switch started acting perfectly and I have idiot lights coming on like I should (although ALL my idiot lights are coming on still, not just the ones I would expect). Also not getting switched power to my ECU but I traced the issue to the jumper harness I made for my swap so that is the next step.

Thanks so much man, I knew it was something simple but man you pointed me right to it. Now I have to start in on my ECU circuit wiring but that should be easy enough.


Quick side question, if one were to remove the ECU entirely and turn the key to ON would all the idiot lights come on like Im seeing? What I mean is, if the ECU wasnt getting switched power when the key is ON, would the idiot lights all come on? Sorry if this should be obvious, this is my first 7 and Im still learning what should be considered "normal". Thanks again!!

satch

iTrader: (1)

The idiot lights come on w/key to on and engine off because a wire from the alternator "should" have a ground on it and this ground signal runs to the idiot light cluster which causes the lights to turn on. When the car is running the ground signal ceases and the lights turn off unless there is a problem w/the alternator and in that situation the lights would turn on.