MMI switches off after 30 secs or so
 

Hey guys been a while since I have been on here. So hello everyone.

Have a couple of issues with my A8.

But the most annoying one is this.

The MMI is working intermittently. It comes on when i turn the engine on but then switches off after about 30 secs. If i turn it on it will just go off again. However, if I have been driving for 30 to 40 mins and try turning it on, it sometimes will stay on.

With vag com i get the faults...intermittent break in optical loop at the can gateway and at the MMI module.

Does this mean that these two are faulty or the control head in between the two is faulty.

Any advice and help on this matter would be appreciated as present playing russian roulette with the MMI is becoming frustrating.

It could be a damaged optical cable, it could be a faulty power connector on one of the units on the MOST optical loop causing the loop to go down. Invest in one of these optical loop backs and start investigating.

http://www.ebay.co.uk/itm//322054880755

Start testing the MMI with one unit out of the optical loop until the MMI seems to be working as it should. If it works then the module that isn't in the loop could be faulty or have a damaged connector on the unit. Should the switching off persist then it could be a damaged optical cable along a run. If the loop is fine then you may have a possible faulty control head, and lastly a faulty CAN gateway (but I believe the CAN gateway will be fine as other errors will show up)

Control head
 

Well I decided to disconnect the optical cable from the control head and see what faults were logged. And the same faults were recorded all be it permanent rather than intermittent. So I think the control head must be faulty. I will look to change the control head and things should be fine then.

Thank you though your advice was really good.

Component Protection will kick in with a new or used control head installed.

component protection
 

Yes i was aware of that and i find it sooooo annoying. I might try buying the optical loop tester thing you linked and just put that and see if it continues working. Which might save me from trying to replace the control head as otherwise it seems to work normally without issue.