Audi A4 B5 electrical gremlin.

renofan · 04-02-2014 11:01am #1

Bought a '00 A4 B5 1.8 last August. On the test drive I noticed "fuse" showing on the dash and was told that all the background lights for switches/temp control dial and light switches in headlining stay on permanently if fuse no. 15 is left in. It also holds the memory for the date/clock on the instrument cluster.

It should be a 10 amp fuse and when I got the car home i put a 5 amp fuse in it and left it in permanently as the word "fuse" was overriding the trip meter and also if the fuse is out you don't have the date/time working which I found annoying. To this day the fuse hasn't blown and all the bulbs are diodes/leds so don't draw much power.

The info in the hand book for fuse 15 says instrument cluster.

I can't find a wiring diagram to see if there is a relay in the circuit that could be gone? The lights in the electric window switches on the doors go out alright but thats it.

Also I should mention that someone put a new radio in and it's not done 100% as it doesn't come on or go off with the ignition switch, you need to manually turn it on/off and therefore works with no key in the ignition. Would this be a cause either? I think it may be but not sure how to wire the radio up right.

Tbh I haven't looked at anything yet as the problem doesn't really bother me but I suppose it'd be nice to get it fixed!

Chimaera · 04-02-2014 11:28am

It'd probably be a good start to find someone with VAG diagnostics (not just an OBD/EOBD code reader) and run a scan to see if it points to any faults.

The Haynes manual will have a good set of wiring diagrams in it and they're not that expensive.

I'd definitely rewire the radio properly before going any further. The VAG wiring tends to be done, weirdness in the radio power supply can cause all sorts of strange behaviour. Particularly, check if the radio has a pin for powering a retractable antenna and where it ends up on the vehicle side. VAG use that pin for something else (can't recall offhand) and sending power back up it can do strange things.

renofan · 04-02-2014 11:31am

I have a haynes manual but it has nothing on the wiring for the above. Will look at the radio on Sat if I have time.

Chimaera · 04-02-2014 1:12pm

The wiring diagrams won't show the internals of the instrument cluster, but they should have the pinouts for the connectors to it. Those diagrams are a little tricky to read if you're not used to them.

Interslice · 04-02-2014 2:32pm

What's your engine code? I'll see if I have diagrams for it.

renofan · 04-02-2014 3:53pm

Interslice wrote: »

What's your engine code? I'll see if I have diagrams for it.

It's an APT engine. Thanks!

Interslice · 05-02-2014 2:32pm

renofan wrote: »

It's an APT engine. Thanks!

I've all the relevant ones there for a passat alright but not an A4 unfortunately. Your welcome to them if want, just PM me your e-mail address. I'm not sure how similar the two are.

dougie-lampkin · 05-02-2014 7:13pm

I have the diagrams for your car, but it won't tell you much. I've attached the fascia and radio diagrams if that helps you. There's 4 radio options, I've included the Bose one, but if you know what the original was I can get that.

From a quick look, this might be similar to your problem: http://www.ross-tech.com/vag-com/aftermarket-radio.html Basically the harness on the factory radio looks like a standard ISO, but it doesn't conform to ISO standard. There's a serial communication line going to the radio for diagnostics, but when you plug in an after market radio this gets shorted to 12V. This could potentially cause all sorts of bugs, especially if someone has tried re-pinning the connector to fix the ignition power issue. You should cut this serial line when using an aftermarket radio, as the diagnostics can't interface with it anyway. In my diagram below it's the pin marked K on the topmost connector. It's easily found behind the radio, the connector has the same shape as it does in the diagram, with the offset locating pin. Just cut the wire a couple of inches back towards the loom and tape up both sides. I think this is likely your issue.

To fix the issue of the radio not turning on with the ignition, you need to swap the pins labelled + and S on the diagram. The radio is getting power constantly, when it should only be getting power from the ignition switch. You might be able to remove the pins from the connector, but if not you can cut them both a couple of inches back and re-join each to the other wire.

Wiring-Diagram.jpg?t=1269238951

renofan · 06-02-2014 10:30am

Thanks for taking the time to write that post dougie-lampkin. Hopefully I can get a look at the car on Sat.

renofan · 22-02-2014 12:59pm

Had a look at the radio wiring earlier and this is what I'm faced with. The radio in it at the moment is a new JVC unit with one din.

The wires to the left are for the speakers and are ok. The wires on the right seem to be the power ones. The red/blue one is live all the time, even with the ignition off. The yellow and red wires were wrapped around the red/blue wire which in my limited knowledge doesn't seem correct. Only wrapping the yellow or red on it's own means the radio doesn't work.

Also the thin blue/grey wire is continuously live too but was not connected to anything.

The brown wire coming from the dash is connected to the black wire on the radio.

I'm a bit stumped to be honest!

renofan · 24-03-2014 11:31am

Just as a follow up on Saturday I rewired the radio to the ignition so I now have a proper functioning radio but the dash lights are still staying on!

I'll be going to get an airbag light reset on the car soon so will see if anyother codes are showing up.

Audi A4 B5 electrical gremlin.

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