Hi everyone, I've been having an intermittent issue with my 2007 Audi A3 1.6 TFSI, where I turn the key and there is absolutely no noise except from the dash. 

When the car doesn't start I experience that:
- Multiple lights will come on the dash, at first, as usual, the TCS, Battery and ABS lights will come on, however the Check engine will not, then after a few moments the EPC, Airbag and Power Steering lights will turn on and stay on as well as the aforementioned lights.

- The car will also on the dash alert Brake fault and the fuel estimation will always read 0km remaining despite the car having fuel and the fuel gage reading correctly.

- The OBD port will not have any power supply and does not read any voltage with a Voltmeter and will not respond to OBD scanners.

- The car will not start even with a jump pack connected.

- No noises from the engine at all.

- Aircon always enters economy mode and doesn't blow anything.

- Accessories usually wont turn on, however when they do the car starts the next time the key is turned.

 

 

When the car does start I find that:
- There are no stored codes.

- The engine cranks more than usual to turn on.

- The key becomes super hot.

- The car doors unlock and the headunit turns off when dropping below 1.3k revs.

- The car doesn't turn off while driving an the lights do not dim, the aircon doesn't faulter either.
 

I have taken it to both a mechanic and an auto electrician recently however it doesn't fault when they are looking and they can not find anything wrong with it, they both have said they have tested the battery and alternator and found no fault, the auto electricians said they couldn't see anything that wouldn't allow it to start despite having it for 2 weeks and the mechanics believed it was a fuel pump relay and replaced it however it hasn't changed anything.

 

Attached is a video example of what the dash shows when not starting.

 

The one symptom that stands out to me is the key becoming hot. That can only be caused by a high resistance at one of the switch contacts, and may be responsible every other symptom. I suggest you get the ignition switch replaced or repaired as the first step.

3 minutes ago, cliffcoggin said:

The one symptom that stands out to me is the key becoming hot. That can only be caused by a high resistance at one of the switch contacts, and may be responsible every other symptom. I suggest you get the ignition switch replaced or repaired as the first step.

I have it booked to the mechanic for Wednesday, I thought it may be, will get it replaced and will report back, thank you!

Good luck with the switch. I suspect they are scarce for an 18 year old car.

7 minutes ago, cliffcoggin said:

Good luck with the switch. I suspect they are scarce for an 18 year old car.

Thankfully it seems that parts are weirdly abundant/easy to get here in Australia, it is quite a steep-ish price however

Any news on this matter Lachlan?

Apologies, still trying to sort it out on my end, mechanics receptionist told me that they could replace ignition switches when booking it in, mechanic told me that they could not when I took it in, and that they didn't have me scheduled in for that day, not great.

Now have to wait for my local Volkswagen Centre to have a look at it, they said they can quickly get it in and diagnose it/confirm that it is the ignition switch in the following days but they are unsure about getting the part in and repairing it before trading for the month ends, maybe having to wait till the 2nd week of January.

However, they did say that the ignition switch moving out of place/corroding is a unusually common issue for older Audi's and VW's in my part of the world, something about the heat and high humidity causing them to corrode faster, and after hearing the symptoms of the car they seem pretty sure it is the switch too.
 

Will have confirmation hopefully Tuesday (Monday your time) and will let you know then. Thank you for checking in.

Edited December 5, 2025Dec 5 by Lokis_Back

1 hour ago, Lokis_Back said:

 mechanics receptionist told me that they could replace ignition switches when booking it in, mechanic told me that they could not 
 

We have a similar problem in this part of the world. It's one of the reasons I favour small independant VAG workshops. You get more sense from the man with dirty hands.

Hey Cliff, finally got a solid diagnosis on it from a local VW Centre, turns out it's the CAN bus module in the car, the technicians told me that with switch failures usually there would be other solid evidence with the car such as it would turn off while driving etc. which is hasn't done so far.

They are replacing the whole gateway module on the car to be safe, getting a VW genuine part from Germany, the part being about 650 AUD (I'd say about 325ish GBP) so its not too bad I suppose. Thank you for the help.

Glad to read it Lachlan, though I don't understand how a faulty module can make the key hot. I guess that's why I am not an electrician.