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D3 - Axles, Brakes, Suspension and Steering Brakes, Springs, shocks, steering racks, steering columns, suspension arms, wheel hubs etc. |
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Thread Tools | Display Modes |
#1
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How to check if an A8 has servotronic, plus, where is the relay?
A8 4.2 tdi lwb 2008 - I assumed it would have servotronic. Checked the relays under the passengers feet and the ones behind the fuse box up under the dashboard. No sign of relay 605 anywhere. On vcds I just get “module not responding” - seems to me it doesn’t have servotronic, but I thought they all did after the .3 revision in 08?
Thanks in advance. |
#2
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Do you still have the build sticker in the spare wheel well? If so, check for QZ0 (QZ* is power steering related) and 1N3 (1N* is also power steering related).
EDIT: According to the '06 brochure, all A8s had Servotronic.
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2001 A8 D2 FL 3.7 Q - LPG Conversion, Engine: AKC, Gearbox:FBB, Colour:LY5X Aqua Blue pearl effect, Interior:WJ light beige/dark beige valcona leather with burr walnut inserts My DIY jobs - Replaced alarm horn, Replaced Coolant Temp sensor, Updated RNS-D firmware, Installed Reversing Camera and Digital TV, Dashcam Installation, Retrofitted Rear Blinds, Auto-Dimming Rear View Mirror, Chrome Boot Struts Sold! 2008 S8 D3 5.2 V10 - Engine: BSM, Gearbox:KLW, Colour:LY7F Suzuka Grey Pearl Effect, Interior:Black/Black with Silver/Black valcona leather with carbon atlas inserts, Bang & Olufsen, Heated windscreen, Soft-close doors, TV, DAB, AMI, Quad Zone, Auto Boot, Auto dim Mirrors, Keyless entry, PDC with rearview camera, AFS II Headlights My DIY jobs - Fan Jet Windscreen Washers, Retrofitted Electric Side Blinds Last edited by steamship; 22nd February 2023 at 05:34 PM. |
#3
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Fantastic thanks I will take a look this evening and report back. Assuming it does have it where the heck is the relay?
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#4
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Quote:
51-SSP 285 Running Gear in the Audi A8.pdfhttp://forum.a8parts.co.uk/attachmen...1&d=1420368035
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2001 A8 D2 FL 3.7 Q - LPG Conversion, Engine: AKC, Gearbox:FBB, Colour:LY5X Aqua Blue pearl effect, Interior:WJ light beige/dark beige valcona leather with burr walnut inserts My DIY jobs - Replaced alarm horn, Replaced Coolant Temp sensor, Updated RNS-D firmware, Installed Reversing Camera and Digital TV, Dashcam Installation, Retrofitted Rear Blinds, Auto-Dimming Rear View Mirror, Chrome Boot Struts Sold! 2008 S8 D3 5.2 V10 - Engine: BSM, Gearbox:KLW, Colour:LY7F Suzuka Grey Pearl Effect, Interior:Black/Black with Silver/Black valcona leather with carbon atlas inserts, Bang & Olufsen, Heated windscreen, Soft-close doors, TV, DAB, AMI, Quad Zone, Auto Boot, Auto dim Mirrors, Keyless entry, PDC with rearview camera, AFS II Headlights My DIY jobs - Fan Jet Windscreen Washers, Retrofitted Electric Side Blinds |
#5
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Here is the sticker. Can’t find either code.
Oddly when I rang the dealer to buy the servotronic relay he gave me part number 4D0907307 - and a quick search shows that on the Audi A6 of similar year some people don’t like the feeling of the extra assistance so have either removed the relay or rigged up a switch to knock it out when they want. I have another D3 that’s a 2006 car which I’m almost sure doesn’t have servotronic and the steering on the 2008 feels the same weight wise, hence me thinking the relay could be worth changing. |
#6
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Looking at that really cool document you linked to I think that they’re handling the components a level closer to the action than the relays and fuses, hence no mention of them. I expect it will need the relay though to actually power the system once logic decisions are made by the processors.
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#7
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The servotronic valve is controlled by a 6V PWM signal so its entirely feasible to control it with the body module instead of having a dedicated unit used in earlier models.
There is a noticeable difference between broken / inactive servotronic and standard steering. I pull the control module in my D2 S8 for track use as it reduces assistance and adds feel. |
#8
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Assuming that the brochure is correct and all A8s came with Servotronic, maybe that's why it's not listed on the build sticker - I never thought about that.
Strange that they gave you that part number as it's for the PF D2.
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2001 A8 D2 FL 3.7 Q - LPG Conversion, Engine: AKC, Gearbox:FBB, Colour:LY5X Aqua Blue pearl effect, Interior:WJ light beige/dark beige valcona leather with burr walnut inserts My DIY jobs - Replaced alarm horn, Replaced Coolant Temp sensor, Updated RNS-D firmware, Installed Reversing Camera and Digital TV, Dashcam Installation, Retrofitted Rear Blinds, Auto-Dimming Rear View Mirror, Chrome Boot Struts Sold! 2008 S8 D3 5.2 V10 - Engine: BSM, Gearbox:KLW, Colour:LY7F Suzuka Grey Pearl Effect, Interior:Black/Black with Silver/Black valcona leather with carbon atlas inserts, Bang & Olufsen, Heated windscreen, Soft-close doors, TV, DAB, AMI, Quad Zone, Auto Boot, Auto dim Mirrors, Keyless entry, PDC with rearview camera, AFS II Headlights My DIY jobs - Fan Jet Windscreen Washers, Retrofitted Electric Side Blinds |
#9
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Ahh fantastic info thanks. Yes, it is odd but then I am not having a lot of luck with my local dealer in many respects so it doesn’t surprise me. To be honest they’re really only interested in oil changes and sending pictures of tyre tread depths!
Assuming now the car doesn’t have the relay and isn’t producing any errors I’m going to declare it fit for service in that department. Because of the demanding access to the PAS reservoir in the 4.2 tdi it was clear that the car had never had any attention at all to fluid changes - the fluid was like treacle and smelled burned to death. Steering was heavy and inconsistent, hence me ordering the relay as a precaution. I sucked the fluid out of it and refilled it several times, running the pump from lock to lock several cycles each time - gradually the steering improved and the colour of the fluid lightened and became clear. I think I went through 2 litres of CHF to get to that point. The steering feels perfect now (I can’t properly test it as the sunroof and headlining are out at the moment) so I think we have a result. Thanks so much for the thoughts and input. |
#10
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After a little more digging I found this table, attached, and the pic of inside one of these “relays” - it’s clearly the control module on the earlier cars, as it contains a lot of stuff which presumably later was moved to the valve on the rack.
Apparently the later servotronic module i have had the “boost” reduced in response to complaints from customers about too light steering, hence the earlier one was superceded. That’s all on pre 2003 cars though, as per the table. What I still can’t understand is why vcds can’t find the steering assist module on my car. Maybe I’m looking at the wrong module in vcds. I’ll have another look. |
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