Audi B7 "Press clutch to start engine" not going away

Hi all,

I've had this car running and working before, so this is really stumping me. When going to start my Audi, everything seems all good. Dash lights up, display comes on. The familiar message displays, "press clutch to start engine". Today though, when I press the clutch and turn the key, nothing happens except an audible click from the engine bay.    

First thought was no battery juice. Put it on to charge overnight, got the same result next day. 

Next though was clutch sensor switch. There are 2 of them under the dash, pulled and tested Ohms with them both on a multimeter. As soon as the switches are hooked up multimeter displays 0.00 (rather than the default ohm symbol), pressing the switches doesn't change the reading. What makes me think these switches are still good is that I had this running about 2 weeks ago with no issue, and I haven't moved it or changed anything in that time. 

Except for the slave cylinder, which I now have out of the transmission, it was still in when working before. It's still hooked up to the lines, just not actuating anything if that makes a difference? I would have thought the clutch switch on the pedal is the only safety thing in the clutch system, but I might be wrong.

Third thing was the starter. Pulled it completely out and hooked it up manually with jumper cables, applied 12 volts to the "key" pin. It loudly clicked as the bendix popped out, but didn't spin. Turns out I had a bad connection, eliminated a couple links in my wiring and got it to spin and work just fine. After reinstallation though, had the exact same result. 

In summary, there's two problems. First is that the car doesn't seem to recognize when the clutch is pushed in, second is that the bendix comes out of the starter, but it won't spin when hooked up to the engine. Not sure if they are related, could the clutch not recognizing be causing the engine to not spin over? 

Any help appreciated. 

In reply to Leviathan888 :

I always kind of thought that the point of a switch was to make and break a circuit.  If they're never breaking, then I would assume they're broken.  But it's weird that they have two switches and they're both doing that.  If clutch released closes the circuit I would assume that having the switches unplugged should resolve the problem if the switch is bad, right?  Unless it's some sort of fancy resistance-based measurement and not just an open/closed thing.

In reply to wae :

The switches are just an analog on off type switch from what I can tell. Ohms might not be the right measuring unit for this specific car, maybe I'll try inputing voltage and or continuity? I rellay doubt the switches are the issue though, due to the reasons stated. 

Find out which one is the interlock and bridge the wires. 

In reply to Slippery :

Don't know what you mean with interlock, but I made a connector to bridge it. Still didn't change anything

In reply to Leviathan888 :

That is what the switch is called. It prevents you from starting the car until the clutch pedal is depressed. 

BTW, did you get the shifting issue figured out?

In reply to Leviathan888 :

Wait wait wait, you have the slave out? It might have a switch inside the trans on the clutch fork. Man you really need to put this things all together the way its supposed to be. It's really hard to diagnose a car that's half pulled apart.

In reply to Javelin :

I know, sorry about that. The reason the slave cylinder is out of the bell housing is because I took it out to rule out another problem, and promptly broke is while taking it apart. An OEM replacement is on its way, will be here by the 28th. 

I hope there's another switch in the bell housing and that is my issue, I've just found lots of other people with this sort of starting problem and hoped there might be an easily available fix. Out of ideas, so gonna wait until the replacement slave arrives. 

In reply to Slippery :

Sadly I haven't yet. Hopefully the replacement slave fixes it, while I haven't ruled it as the issue it well might be, the old one felt kind of weak and this car has been driven really hard. If the part does not fix it, I'm gonna drop the tranny as the problem should be easily visible then.  

Clutch switches are, traditionally, simple on/off. The circuit is open (off) when the clutch is up/not pushed and closes when you push the pedal far enough.  
 

if you can see that the pedal is moving far enough to close the switch and have tested it for continuity when it is closed, you're probably fine.  But you can double check by probing for 12v power on both sides of the switch when the clutch is depressed and the key is in run. 
 

that's assuming it works like a traditional switch.  I can't speak to yours in particular.  But you start with simple solutions and the safety switch would be the place to start if it is asking you to push a pedal that is already pushed. 
 

looking for another switch somewhere (as suggested) would be my next step if you verify that the switch is working. 
 

also, dismissing the switch because it ran fine last time is silly - SOMEthing changed in the two weeks it sat otherwise you wouldn't be getting the warning!

Pressing the switches doesn't change the reading? Weird. And you bridged both switches or did you isolate which is for the computer and which is for the starter interlock?

A lot of "switches" in newer cars are really position sensors.  Even if they only work on/off, they may have some internal resistance factor so the module it is talking to can tell the difference between on, off, open wiring, or shorted wiring.

Also, a lot of "switches" are Hall effect sensors, which not only makes the diagnosis above easier, but in theory won't ever suffer from dirty contacts.

This is where service info is super important, as far as testing is concerned.  Or even just a scan tool so you can see the data that the computer is seeing.

In reply to Pete. (l33t FS) :

Yeah I might get an OBS or whatever scan tool to read the codes and see if it reveals anything