Electrical problem?

[Kian]

Hi guys, having a problem with my B8 a4, and hoping someone can help me out.

so as the car sits now, I have no electrical power to anything inside the car, ignition, ac, radio, windows, mirror adjust, lights, nothing works, so I can’t even start the car, on get power to do any kind of diagnostics. Inside is “cold and dark”.

I can use the key to unlock the car, however, only the drivers side doors and boot open, my car is right hand drive, the passenger side doors stay locked and cannot be opened from the inside either.

The drivers wing mirror indicator and both tail light indicators will flash for unlocking, nothing else does, and nothing flashes for locking, but everything locks. And on top of this, the interior light in the boot/trunk works.

this problem has happened 1 week ago, so I changed the battery and I checked the altenator voltage during the week, as the car has been driving fine fine this week since changing the battery and everything is reading perfect, and when I lost all my power last night, I checked the battery with a multimeter, and I’m getting 12.6V from the battery itself and from the lugs under the bonnet.

im really at a loss at the moment and have no idea what this could be. Any help of advice would be greatly appreciated.

TIA

 

[jakm15]

If it was me in that situation I'd be checking the battery connections first to make sure there's none of the negative or positive connections come loose or wires come out when the battery's been changed.

I'd then check all the main fuses at all the different fuse boxes to make sure non have blown

If all those are ok I'd disconnect the battery fully and stick it on charge overnight then reconnect it and take it from there.

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[Kian]

I put the new battery in myself last Saturday and the connections seem fine, I haven’t checked any of the fuses myself, the car is with a mechanic now so I’d imagine he will do that.

 

[jakm15]

I put the battery in myself and the connections seem fine, I haven’t checked any of the fuses myself, the car is with a mechanic now so I’d imagine he will do that.

Keep us updated on the results in case anyone else has this issue, it would be interesting to know what has caused it.

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[Kian]

Keep us updated on the results in case anyone else has this issue, it would be interesting to know what has caused it.

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Will do

 

[AndyH701]

In your engine bay fusebox you have a set of relays. The one closest to you, if you stand by the drivers side, in the biege connector.
If this relay has yellow writing on (the small writing not the large 645) Audi themselves recommend you replace it with a later white writing relay.

The yellow ones are prone for malfunction. If tis relay doesn't provide power, your car will be kaput as you describe.

Your mechanic can easily check power going into it by the red cable attaching to the relay box.

This is where I would start

 

[Kian]

Cheers Andy, I’ll pass on the message to him and update here if it’s makes a difference.

 

[desertstorm]

That's very interesting information Andy and very useful. Did a bit of a dig and found this.

 

[briceportier]

Same happened to me after retrofitting the start/stop button. Took me 5 unnerving days to find out what the (ridiculous) issue was and I really thought I'd f...ed something up
Turns out the key reader/module 5A fuse was blown...

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[Kian]

Do you know where that fuse is off the top of your head?

 

[Kian]

UPDATE: so my mechanic says he tried the relay that audi mentioned goes bad, and he tried all the fuses, all is good with them.

however it turns out a previous owner has messed with the cars wiring, and he reckons this has caused the problem.

I’m calling out later to him so I can find out more.

Kian.

 

[Kian]

So it turns out someone was messing with the wiring in the boot/trunk and installed some sort of switch, and routed it from the positive side of the battery with no ground, and the ECU was messed with.

The fuse box on the drivers side of the dash, my car is right hand drive, had no power going to it.

 

[Kian]

 

[jakm15]

View attachment 196115 View attachment 196116

That's a strange one I wonder what it's for or was for.

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[Kian]

I’ll try and find out if I can, yeah it’s very strange

 

[***DK***]

Could it be a fuel pump kill switch or some other kill switch to stop people stealing it?

 

[Kian]

Could be something like that alright.

 

[jakm15]

It looks very similar to the switch on my caravan that isolates the positive feed from the battery to the motor mover.

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[desertstorm]

Looks like somebodies idea of an immobiliser and it seems to be working. I would have thought either to stop the car being pinched or possibly stops the battery from discharging if the car is left for a long time . Are there extra wires at the back of the switch?. The large silver finned module behind the switch is the amp for the speakers. Possibly somebody has had a large sub in the boot ? Either way certainly looks like it may be related to the issue you have now. Good luck.

 

[NHN]

Those kroschu wires are heavy duty, are they OEM as don't appear so.

 

[Kian]

Nothing OEM about it, my mechanic has removed it and car is back to normal.

 

[AndyH701]

That is a positive kill switch.
The big red key is how its activated.
You'll see those on all forms of motorsport cars. The idea is to kill all power to the car quickly in the event of an accident. The spare wires on the back are extra 12v cut offs incase the accident creates shorts, usually ignitiom and fuel pump circuits

To see one on a regular road car is as the others have guessed, to immobilise or to 'turn off' when left for long periods. Glad its been fixed