I've been chasing a problem and just when I think I got it fixed it will re-occur
It started when out of nowhere my a6 wagon just wouldn't turn over. Power to everything seemed good. So I replaced the ingnition switch...nothing
I eventually pulled the starter ( the ground to the starter from the selinoid was fried or corroded looking) and replaced it and put in a new battery and cleaned the engine to chassis ground. bingo, car started ran great for a few days then bang all of a sudden same symptoms. I went over my work and just happen to jiggle the engine to chassis ground and it started. replaced the ground wire and everythings was back to normal ....for a few days but again all of a sudden no start. check that ground wire again and by bending it around a little i got the car to start. Replaced the ground wire again thinking i may have damaged it by twisting it too much to fit on its mounts but now nothing. Audible click when I turn the key comng from the starter but nothing. tried whacking the selinoid but still nothing
I appreciate any help on this. I'm at the end of my game with this
Thanks

 

Sounds like low power to the starter, check the primary wiring again, you've missed something, or your battery is discharged. A solenoid clicking is getting 12 volts but not enough amps to turn the starter. It is possible th earter is bad too, rebuilt ones can be marginal sometimes.

 

Clean your battery terminals once again.

Bob

 

thanks for the responces
i agree it must be electrical and seems to center around the ground wire from the engine block to chassis.
i've replaced the original with an aftermarket #4 gauge lead
But i wonder if it not correct for the car as I have been able to only get random turn overs from the starter

 

Don't you have a volt meter? Just check the volt drop from the positive lead on the battery to the starter, it should be less than 1V. It is also very possible that you got a bad starter, i got one from Kragen one time that only worked for a week on my A4, POS!
I would grab a 4 gauge wire (or similar) and jump that turd, if it turns over immediately its probably the ground or battery. You can also check the resistance between the negative cable on the battery (cable not connected to the battery) then to the other end of the ground wire where it meets the chassis. There should be almost no resistance on that wire.