Audi A8 electrical fixes

theschmallfella · 22-11-23, 04:00 PM

Hey all, it's been a while since I posted.

As the title suggests I'm after a bit of A8 info. I have a 2000 3.7 quattro in Jasper Green, I bought it almost exactly a year ago from a very nice couple living in Croydon who unfortunately had to sell it due to the dreaded ULEZ charges. It's in excellent condition mechanically, it was minded like a child! Originally sold in Newcastle they were the second owners who had it for 20 years. Interior is excellent although it needs a good valet to clean it up. Bodywork is good, has some slight damage to a rear wheel arch and the usual age related marks.

So a few things aren't working. The headlamp washers, sunroof and cruise control don't work. I've checked fuses and they're all good, are there relays that control these items or would there be some other issue at play here? What are the locations of the relays? Thanks in advance.

A8 3.7 quattro by Luke W Cleary, on Flickr

A8 3.7 quattro by the sea by Luke W Cleary, on Flickr

A8 3.7 interior rear by Luke W Cleary, on Flickr

A8 3.7 interior front by Luke W Cleary, on Flickr

vagdream · 22-11-23, 05:02 PM

As I recall most of the relays on the D2 are located behind the glove box and under the dash on the passenger side of the cabin. I can't recall a relay on the cruise control but you might need to clean up the connections on the dash stalk.

John. · 23-11-23, 11:59 AM

Sorry I can't help with your electrical issues wee man but have to say that's a nice looking luxo barge ! Especially like the 2nd picture.

That ULEZ scheme will cause a lot of cars to change hands.

BackintheFold · 23-11-23, 01:06 PM

I once had an Audi 100 where the cruise wouldn't engage due to a brake switch needing adjustment. Could it be as simple as that?

Hanuman · 23-11-23, 01:28 PM

Pedal switches- clutch, Brake
Column switch. I don’t remember which car, but the switch was loose. Just selecting the turn indicator was enough to trip the cruise.
Is it still vacuum? Broken hose connections, perished tubing.

https://audi.7zap.com/en/rdw/audi+a8.../9/907-907010/
Diagram for vacuum cruise is fairly simple

Pump, pedal switches, actuator.
I’d post the diagram, but Tapatalk doesn’t seem to be working anymore

7zap, diagram for 1999 A8 cruise control

theschmallfella · 28-11-23, 04:39 PM

Quote:

Originally Posted by John.

Sorry I can't help with your electrical issues wee man but have to say that's a nice looking luxo barge ! Especially like the 2nd picture.

That ULEZ scheme will cause a lot of cars to change hands.

Hey John, hope you're keeping well. Yeah she's a beauty, I really lucked out. I've been after one for years but they always seemed to be just out of reach for me. When this one came up I just couldn't leave it behind.

theschmallfella · 28-11-23, 04:40 PM

Quote:

Originally Posted by BackintheFold

I once had an Audi 100 where the cruise wouldn't engage due to a brake switch needing adjustment. Could it be as simple as that?

Good suggestion buddy, that'll be my first port of call so.

theschmallfella · 28-11-23, 04:45 PM

Quote:

Originally Posted by Hanuman

Pedal switches- clutch, Brake
Column switch. I don’t remember which car, but the switch was loose. Just selecting the turn indicator was enough to trip the cruise.
Is it still vacuum? Broken hose connections, perished tubing.

https://audi.7zap.com/en/rdw/audi+a8.../9/907-907010/
Diagram for vacuum cruise is fairly simple

Pump, pedal switches, actuator.
I’d post the diagram, but Tapatalk doesn’t seem to be working anymore

You know i need to do a deeper dive into how the system works, I'm not sure if they run on vacuum like the 200 does, it may be electronic. I'm still very new to the workings of the A8 despite being a fan for years, it's only when you own one do you realise how complex they are.

Hanuman · 28-11-23, 10:33 PM

I realise I wasn’t very clear, as I added that image after I’d posted.

That image is of the system from an A8.

Sandro · 29-11-23, 10:26 PM

On my V8 (which uses same cruise control system) - cruise control was kind of "stuck". I pressed hundred times cruise control button and it started to work. Very often on these the problem is in the switch itself. It looses the contact and no more cruise control.
For the sunroof - same thing. There is relay under the button cover. Take it off, take off the relay, check it, check connectors, check if there is power coming to it. These are pretty simple there.
Faulty headlamp washers might be related to stuck motor in washer bottle. Or just not enough fluid

On late V8's headlamp washer is placed higher up so if fluid gets low, it just does not get fluid

23-11-23, 01:06 PM	#4
BackintheFold Senior Member Classic Audi Club Member Join Date: Feb 2019 Location: Near an MB ur Quattro Posts: 1,171	I once had an Audi 100 where the cruise wouldn't engage due to a brake switch needing adjustment. Could it be as simple as that? __________________ 2006 A3 (daily drive) 1987 MB ur

23-11-23, 01:28 PM	#5
Hanuman Trickster Classic Audi Club Member Join Date: May 2009 Location: Heckling from the cheap seats, Phnom Penh, KoW Posts: 7,006	Pedal switches- clutch, Brake Column switch. I don’t remember which car, but the switch was loose. Just selecting the turn indicator was enough to trip the cruise. Is it still vacuum? Broken hose connections, perished tubing. https://audi.7zap.com/en/rdw/audi+a8.../9/907-907010/ Diagram for vacuum cruise is fairly simple Pump, pedal switches, actuator. I’d post the diagram, but Tapatalk doesn’t seem to be working anymore 7zap, diagram for 1999 A8 cruise control __________________ I wish they would keep the damned Chinese away now that I can go home, so that I can enjoy Fish amok and a draught Angkor Last edited by Hanuman; 28-11-23 at 10:37 PM. Reason: Reposition Image, add note

28-11-23, 10:33 PM	#9
Hanuman Trickster Classic Audi Club Member Join Date: May 2009 Location: Heckling from the cheap seats, Phnom Penh, KoW Posts: 7,006	I realise I wasn’t very clear, as I added that image after I’d posted. That image is of the system from an A8. __________________ I wish they would keep the damned Chinese away now that I can go home, so that I can enjoy Fish amok and a draught Angkor

22-11-23, 05:02 PM	#2
vagdream Grown up member Join Date: Jul 2015 Location: Llandudno Junction Posts: 165	As I recall most of the relays on the D2 are located behind the glove box and under the dash on the passenger side of the cabin. I can't recall a relay on the cruise control but you might need to clean up the connections on the dash stalk.

23-11-23, 11:59 AM	#3
John. 4 ring whore! Classic Audi Club Member Join Date: Mar 2011 Location: Scottish Borders. Posts: 7,520	Sorry I can't help with your electrical issues wee man but have to say that's a nice looking luxo barge ! Especially like the 2nd picture. That ULEZ scheme will cause a lot of cars to change hands.

29-11-23, 10:26 PM	#10
Sandro Grown up member Join Date: Feb 2011 Location: Chelmsford Posts: 651	On my V8 (which uses same cruise control system) - cruise control was kind of "stuck". I pressed hundred times cruise control button and it started to work. Very often on these the problem is in the switch itself. It looses the contact and no more cruise control. For the sunroof - same thing. There is relay under the button cover. Take it off, take off the relay, check it, check connectors, check if there is power coming to it. These are pretty simple there. Faulty headlamp washers might be related to stuck motor in washer bottle. Or just not enough fluid On late V8's headlamp washer is placed higher up so if fluid gets low, it just does not get fluid