Poor quality sound on the audio input can occur after the headunit has changed from a second generation headunit to a third generation headunit or vise versa. The fix is simple and requires some pins to be swapped on the head unit connector.
Second generation headunits
Multi-pin connector 4, 12-pin, for CD changer control and CD audio input signals
1 – Right headphone output signal, positive
2 – CD changer, left and right channels, negative
3 – Headphone output signal, audio earth
4 – CD changer, voltage supply, positive
5 – Left headphone output signal, positive
6 – CD changer, bus DATA OUT
7 – Not assigned
8 – CD changer, left channel, positive
9 – CD changer, right channel, positive
10 – CD changer, control signal
11 – CD changer, bus DATA IN
12 – CD changer, bus CLOCK
1 – AUX signal input, left (yellow)
2 – CD changer, left and right channels, negative
3 – AUX signal earth (green)
4 – CD changer, voltage supply, positive
5 – AUX signal input, right (grey)
6 – CD changer, bus DATA OUT
7 – Not assigned
8 – CD changer, left channel, positive
9 – CD changer, right channel, positive
10 – CD changer, control signal
11 – CD changer, bus DATA IN
12 – CD changer, bus CLOCK
Alternatively it may be wired up to the CD changer inputs.
1 – AUX signal input, left (yellow)
2 – CD changer, left and right channels, negative (green)
3 – AUX signal earth (green)
4 – CD changer, voltage supply, positive
5 – AUX signal input, right (grey)
6 – CD changer, bus DATA OUT
7 – Not assigned
8 – CD changer, left channel, positive (yellow)
9 – CD changer, right channel, positive (grey)
10 – CD changer, control signal
11 – CD changer, bus DATA IN
12 – CD changer, bus CLOCK
Third generation headunits
Multi-pin connector 4, 12-pin, for CD changer control and CD audio input signals
1 – AUX signal input, left (yellow)
2 – AUX signal earth (green)
3 – CD changer, audio signal earth
4 – CD changer, voltage supply, positive, terminal 30, contact continuous load greater than 1 A, temporary peak load 5 A
5 – Not assigned
6 – CD changer, DATA OUT
7 – AUX signal input, right (grey)
8 – CD changer, left audio channel, CD/L
9 – CD changer, right audio channel, CD/R
10 – CD changer, control line, switched positive
11 – CD changer, DATA IN
12 – CD changer, CLOCK (internal check protocol for data flow monitoring)
Multi-pin connector 4, 12-pin, for CD changer control and CD audio input signals
I have an 09 Jetta TDI where I swapped the factory-installed Premium VII 6-CD head unit for an RNS-510 and an MDI retrofit kit using the Kufatec harness for MDI. Are the gren and gray AUX pins already swapped in the Kufatec harness, or should I now swap them on the HU connector?
Here is another write up with some pics on VWVORTEX
http://forums.vwvortex.com/showthread.php?4696811-Pics-of-aux-input-wiring-for-RNS510-from-non-nav-car&p=67061697#post67061697
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