Ignition electrical glitch

tagscuderia

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https://1drv.ms/v/s!As_InXsv42i2hKhB5BiuYZHsxK8RdA
Onedrive link to video

Completely out of the blue my FSi has thrown a spurious electrical glitch at me, I'm apprehensive to use the car (so as not to risk further damage) and naturally tax/insurance/MOT are all due next week :(

The linked video shows the key being turned to ignition ON and leaving it there. At the end of the clip I attempt to start the car which fails (immobiliser?) but the clocks then behave?! The noise in the video seems to be emitted from behind the central vents but it's difficult to pin down.
The car will start after repeated attempts and continues to run fine; I drove 200 miles yesterday to get home, no hiccups.

I love my A2 but it's been hugely expensive to keep on the road these last 2 years. But that also means that I'm 100% invested so... anybody got any ideas?
Much appreciated, thanks guys/gals.
Tom.
 
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P.S, I have been battling to solve irregular idling as well as rough, high revving for both cold and warm starts and during last night's journey I noticed that the interior lights pulsed somewhat with the wavering engine revs whilst idling; I'd pulled over to study a Road Atlas. I don't know if any of this could be connected...
WOM have had the car twice and haven't been able to solve the engine issues - no fault codes, I imagine that there'll be a fair few now!
 
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I have been battling to solve irregular idling and high revving on both cold and warm starts and last night noticed that the interior lights pulsed somewhat with the wavering engine revs whilst idling; I'd pulled over to study a Road Atlas.
I don't know if any of this could be connected but WOM have had the car twice and haven't been able to solve the engine issues unfortunately - diagnostics don't report a fault :confused:

Hi,

If idling revs are too low then that will cause the voltage generated by the alternator to fall below 12v just because the engine is running too slowly. However, if the alternator output isn't high enough, the low volts will cause the engine to idle irregularly rather than the low volts being a result of low revs.

I have a similar problem with my 1.4 petrol, I would expect the 1.6 ECU would do the same thing. The ECU tries to keep the volts high enough to ensure that it and the engine electrics are running correctly. If the alternator isn't outputting properly, the volts can drop below 12 when the engine is running slowly (i.e. at idle). If the ECU sees the volts drop, it will increase the fuel timing to increase the revs. When the revs go up, the volts go above the problem threshold and so the ECU cuts back on the fueling which causes the revs to drop etc. The cycle repeats.

The thing to check is the voltage that the ECU sees when the engine is idling. If its too low then there is probably a problem with the alternator. The voltage can be checked with VCDS. After my alternator was replaced, the engine ran much smoother at idle.

regards

Andrew
 
https://1drv.ms/v/s!As_InXsv42i2hKhB5BiuYZHsxK8RdA
Onedrive link to video

My FSi is feeling its age at the minute, the usual wear related items but... it has now thrown a spurious electrical glitch into the mix!
This has appeared completely out of the blue and I'm apprehensive to use the car and naturally tax/insurance/MOT are all due next week :(

What the video shows is the key turned to ignition ON and leaving it there. At the end of the clip I attempt to start the car which fails (immobiliser?) but then the clocks behave?!
The louder noise in the video seems to be emitted from behind the central vents but it's difficult to pin down.
If I switch between ignition OFF and START, the car will start after repeated attempts and continues to run fine; I drove 200 miles yesterday to get home, not hiccups.

I haven't had a chance to try my spare key (will update tonight) but remote central locking continues to work without fail.

I love my A2 but it's been hugely expensive to keep on the road these last 2 years but that means that I'm invested in all sorts of ways so... anybody got any ideas?
Much appreciated, thanks guys/gals.
Tom.

Hi,

just had a look at your video. The buzzing sounds like a relay, and it looks like the cluster is switching on and off repeatedly. The cluster power comes directly from the ignition switch. The ignition switch also powers a high power relay, the "x contact relief" relay which is used to drive high load items like the interior air blower fan, rear window heating element and headlights. If there is a problem with the ignition switch contacts then this may cause the relay to buzz and also the instrument cluster to turn on and off.

For the engine to run, the instruments have to be operating correctly as they are part of the immobilisor. The cluster has to start up and successfully handshake with the engine ECU to verify that they are both correct. They are paired to ensure that the car hasn't been tampered with. Once this has happened, the immobiliser chip is read in the key and if that's OK, the engine will continue to run. This is completely separate to the remote unlocking and doesn't involve the CCU. As it takes a while for all this to happen, the engine is alowed to start straight away and if there is an immobilier issue, e.g. a key with a chip that isn't recognised or an error reading the chip, the engine will cut out after a few seconds. If the ECU and Cluster don't handshake properly however, the engine may not start at all anyway.

The buzzing sound seems to point to the power problem being external to the cluster, rather than the cluster itself being faulty. If the problem is reproducible and there aren't any obvious problems with corrosion on earth points or connectors, then it may be a worn ignition switch. I would investigate the ignition switched output to see if the supply fluctuates at the same time as the flashing seen on the cluster. If the supply is good and the connectors to the cluster are also good, it may be worth having the cluster checked out by a repair specialist. If someone could temporarily lend you an FSI cluster, you could also see if that does the same when you turn on the ignition (to rule out either the car or the cluster), although you would not be able to start the engine with another cluster as it won't be paired with your ECU.

regards

Andrew
 
Tom that looks like a earth problem, I'd suggest start fault finding by checking all grounds including battery terminals. It's nothing to do with your immobiliser as one, it wouldn't make those noises and two, the little car light (immobiliser) goes out as it should.

Run basic checks on all grounds and even positives for example the positives under the passenger floor and on battery and alternator.



Sarge
 
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Thank you for both of your replies Andrew, greatly appreciated. I have suspected an alternator issue in the past but I hadn't linked it to the idling issue, which fits like a glove now that you've explained it, so the time might be right for new a belt/pulley/tensioner - thanks. I'll test the alternator before replacing ancillaries.

The cluster is obviously getting a disrupted power supply, my first thought was a fault with the ignition barrel but whenever I attempt to diagnose a fault... it's normally something completely unrelated (doh). The cluster functions correctly once it has a constant power supply so potentially a problem with the ignition switch as you've said - sorry to be a layman but how can I " investigate the ignition switched output to see if the supply fluctuates at the same time as the flashing seen on the cluster." I'm happy mechanically, just not very astute electrically.
Thanks again for the help.
 
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Thanks Sarge, I was being dim-witted mentioning the immobiliser but I'll have a good look at Earth points tonight - something that I keep putting off to be fair :rolleyes:
 
Thanks Tom - I've checked the battery, Earth point behind the N/S headlight (visual only, it was getting dark) and the cluster. I can't see any issues but obviously that's not an exhaustive check.
I only tried to start the car a couple of times but... it seems that going from ignition OFF to START (without pausing at ON which is what I've always done) does start the car first time of asking - but I need to confirm this tomorrow.

@Andrew, I think that you're spot on regards the alternator: the revs fluctuate when you put the headlights on and the interior lights dim in sync with the peaks and troughs on idle. Time to find a garage that I can trust locally! Thanks.
 
A visual check on the earth behind the N/S headlight can be deceiving. Any corrosion and consequent high resistance is on the mating faces so any problems there is only discovered when disconnected.

Geoff
 
Thanks Geoff, I will check that earth point properly, simply short on daylight hours (working in the road too :(). Also didn't want to break it, which reads like a common issue, without a replacement to hand!

Edit: I think that I'm going to bite the bullet and replace the ignition switch, it's not an expensive part and it's easy to replace. I also always use the steering lock so that will have added to the wear and tear. Fingers crossed.
 
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Tried the car this morning, ignition OFF to Start without pause and it started first time with zero issue! So this is indicating that the ignition switch is faulty no?
Thanks.
 
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