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Hi I have a 2008 Audi A5 3.2L V6 with about 80k miles. Every once in a while the car wont start. The dash lights work fine along with all the electronic parts of the vehicle. The vehicle doesn't crank at all but the lights come on and when I open the door the dash reads: " Ignition is on ". Its like the car thinks its on but it never started? I usually have to wait for about an hour to get it to start again. After that, it seems to work fine for a couple more days. This problem surfaced about two 1/2 weeks ago. So far this has happed twice.

I need some help!

  • Does it use a key to start or is it pushbutton? Manual or Automatic? There are a few switches to check if the starter doesn't even try to turn. – JPhi1618 Nov 28 '17 at 19:20
  • It is an automatic and is has the push button start and the key insert start. I tried both and it's the same outcome. – Edwin M Nov 28 '17 at 19:28
  • "Ignition is on" just means the car is in "run", not that it thinks the car started. I'm not sure, but if the immobilizer in your key is battery based, could it be a dying keyfob battery? An automatic shouldn't have a clutch or gear position sensor to worry about. – JPhi1618 Nov 28 '17 at 20:08
  • Ok that's good to know. I thought about that but idk. Wouldn't it let me know on the dash if the battery is running low? – Edwin M Nov 28 '17 at 20:11
  • Can you fully charge the battery and see if this stops the problem? – Steve Matthews Nov 30 '17 at 13:07
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Follow a logical procedure, going from easiest to hardest/more time consuming thing:

-check for error codes in the ECU

-check if starter motor gets 12V from the solenoid/relais

-check if solenoid gets signal impulse from ECU

As most intermittent problems it usually is something "about to fail" or some sensor/connection/piece of code working in a "borderline" condition, the above should give you a rather clearer image of the thing. With a bit of googoling you may be able to find complete factory manuals and electric schematics, they help a lot since they enable you to find out the process and conditions required by the ecu to authorize cranking, i.e. a similar problem to yours sometimes happens on R55/6, with the depressed clutch pedal sensor working intermittently and being a required condition for startup.

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    This, and also, starter motors do break and its not quite uncommon. – Daniel Nov 30 '17 at 9:24
  • @Daniel Starter is my first guess. But I don't hear clicking coming from the started. If it were broken I would hear it right? And how can I turn the vehicle on after about an hour? – Edwin M Dec 1 '17 at 7:04
  • @Edwin M If there is no clicking it could be the solenoid itself on the starter motor. Probably not, but since after having excluded the points mentioned in my answer the thing becomes way more complicated and time consuming (you`d need to find the diagrams..) it is well worth to check, – Caterpillaraoz Dec 1 '17 at 8:08
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I have been experiencing a similar situation. Same model and year as OP. No obvious reason for when or why it would occur, no pattern that I could discern, it would just randomly not start whether with the key in the insert position or using the start/stop button. I would have to try multiple times, but after a few attempts/minutes, it would normally start. However, I have found that a simple cure, for my car anyway, if it fails to start is to simply touch the accelerator once, then it starts normally. Might just be a "fix" for my car, but maybe it works for yours as well

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