I've retrofitted an MDI to my Superb with Columbus. I've made my own wiring according to the circuit diagrams in the workshop manuals, but at least on aux in, I get a ticking noise in the background. I didn't hear it on the iPod lead but maybe it was just being too loud.

 

Anyway, before I try to troubleshoot the wiring, has anyone had a similar problem before?

My MDI works fine as long as you don't use the AUX port, if you use the AUX port with the ignition off it's fine too. But when the ignition is on and you use it then it crackles like a TV with a dodgy ariel. My solution. Don't use the AUX port.

Thanks. Will see if it does it on USB now my USB has arrived. It's not a crackle, definitely a repetitive tick.

No noise with USB, so it looks like its the aux input. Odd that I get it with the aux socket, and the aux cable into the rectangular plug. No matter its USB that will get used.

So you have a different noise, but more or less the same problem as me, I wonder what it could possibly be then? Not that is really bothers me any more but still.

Well the fact that there's no noise when using USB, means it can't be the wiring between the MDI and the Columbus. The fact it happens on the internal 3.5mm with the lead into the rectangular socket means it can't be the external aux socket wiring (as far as I can see). So it must be an MDI with an internal fault.

Did you wire the aux in via the mdi pass through pins? (5, 6, 11).

Yes, 5,6,11 and the overall screen to pin 12.

That's correct then, so can't think why you get a tick, especially if screened. Only thing I can think of is either a pin is a bit loose in its socket, or left and right are reversed somewhere. Can't see a faulty mdi unit being the issue as I believe the pass through pins ignore it...

I don't think the pass through pins do ignore it. I think for the analogue inputs (the two aux, and the iPod) the MDI does an analogue to digital conversion, and switches everything in the digital domain. The USB is already digital. So if theres a fault in the ADC section it could cause a problem with everything except USB. Maybe its that.

Yes if that is correct it could be it. The reason I thought it ignored it is that aux is active only if mdi is not. So I assumed connecting it is as mdi is also effectively the on switch. Then if aux is on but mdi is off it is simply pass through.

Thinking again though, if both were connected, aux is not on, so there must be something switching states inside the mdi itself, suggesting you are correct.

I think I solved this one. It's to do with me being unable to count properly. The car is due for a service so I put my VCDS on it which told me that infotainment CAN was in single wire mode. I started looking at the MDI connector and found I'd connected CAN low to pin 3 instead of pin 2. Pin 3 is used on some versions for another audio ground, its unused when installed in a Superb. So I'd connected an audio ground to CAN low. Doh!

 

I haven't checked the noise has gone, but its so obvious now I've cleared the CAN fault that it was just me being a dope!

Sorry to hijack the thread. Im looking to retrofit mdi to my oct vrs 2014 tdi. i have the bolero unit. What do i need to retrofit mdi, part numbers etc and where from please? Also if i remove the battery whilst installing will it cause any problems when i reconnect it - ie do i need to put stereo code in etc?

Sent from my SM-G900F using Tapatalk