Auxiliary input audio sound quality problems after changing head unit

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

volkswagen_rcd_510_main_N91-10016Multi-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)

5 thoughts on “Auxiliary input audio sound quality problems after changing head unit”

  1. 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?

  2. I have upgraded from an RCD300 to RCD510. My golf mkV had an ipod adapter installed with the RCD300 which charged my ipod while it was plugged in, I also used to be able to control the ipod from my MFSW. I have changed the pins and the audio from the ipod is working but it is not charging my ipod now and I cant control it from the MFSW. Anybody know what the issue might be?

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