forum.audiv8.com Foren English Audi V8 Forum Wher is the Cruise control unit plased in the V8 ?

Hello,
Is ther sombody ther know wher the cruise control unit is plased in the V8 ? i think my unit is broken.
If sombody knows how the easy way to replace it, i will be happy if you will writ how to do it.....

best regards
Søren

Hello again Søren,

Here is another email for you; this time from my friend Steve.

Good luck!

Regards,

- Jeremy

--------------------------
On every Audi other than the V8 I've been able to fix the CC with simple measures ... adjusting the pedal switches or repairing vacuum leaks ...
that's still the first place to start in my opinion. You only have one switch on the automatic ... on the brake pedal. Make sure that the switch protrudes enough so that the pad that senses the pedal is fully depressed against the switch body when the pedal is released.

I've seen problems with integrity of the vacuum system that drives the actuator. If you pull the vacuum line from the pump and apply a vacuum there you should observe the throttle actuator motor get pulled in. If you don't have a vacuum pump you can depress the actuator motor and then pinch off the end that attaches to the pump and the actuator should remain in position when released. If you do not find this to be the case ... check to see that the pedal switch isn't leaking (in my experience a sign of a need for
adjustment) or look for a broken "T" fitting in the system near the CC actuator. Of course, check that the linkage rod is attached to the throttle body linkage while you are doing this. Unfortunately most of this stuff is buried behind the engine on the left side.

There is another bizarre possibility which you may want to investigate ...
the CC uses the "hot" side of the brake light circuit to get its ground. It is a fail safe measure, that way when the brake lights come on the CC is guaranteed to lose its ground. If you lose all your brake lights the CC will stop working too ... check to make sure that the brake lights are functional.

One other peculiarity of the automatics is that the CC power is enabled by the tranny computer, so if you have any tranny codes it may disable the CC ... read out tranny codes and get them cleared.

Now ... to what I found on my car ... None of the simple stuff solved it so I followed the troubleshooting guide in the book. I found the ON/OFF switch was bad ... I replaced it and the car now has CC. Given your situation, if you suspect that the problem is due to a bad switch or the tranny ECU you might want to install a temporary fix by supplying a direct switched power connection to the Cruise Control system. I do not think there is a big risk to doing this ... I drive around with the CC on most all of the time anyway ... If you want help in figuring this out get back to me and I'll get the wiring diagram out and figure something out ...

I've never had a situation where the vacuum actuator, vacuum pump or CC controller has been the cause of a failure ...

I hope you have a very safe trip out and back ...

Steve Buchholz
San Jose,

Hello Steve and thank you for you’re time.

First sorry my bad English, I hope you understand it )

My CC is working sometimes, but it is like the lottery ) and sometimes when i have drive the car for a time then the CC is stop working and for the most I can’t get it to work again but it is like the lottery here to ).

I have testing the Vacuum system for leak, all is ok (no leak at all)
The vacuum pump is also ok, an there is no leak when the switch is activate, when it get directly power from the battery .
When i drive more than 35km/t there comes power on the fuse (26) so this part is also ok.
(there is also power on fuse (26) when the CC is not working !)
When the CC is working there is a “klik” sound from 1 or more switch, but when its not working there is no “klik” sound at all.
My break light is also ok.
I have try to replace the switch for the braking pedal, but it don’t get better.
(My V8 have Automatic gear box so ther is just one pedal switch on it)

My auto repair say he think it is the CC control unit, but I think it is a broken cable problems, or a bad ground.
When the CC is stop working, I can’t get it back to working if I push the on/off or all the other switch i have try it many times.

I have the diagram for the CC.

If I shall check the CC controller unit (I have one from another car) do you know where it is and the easy way to replace it ??

Best regards
Søren

The CC Control Unit is behind the glovebox on the passenger side. If you have a spare, you might as well try installing the other one.

Also, when you are driving, if you lift up the brake pedal with your foot a little bit, does it allow you to operate the CC? If so, it could still be the switch adjustment on the brake pedal.

Good luck,

- Jeremy

Sorry at i call you Steve
Thanks for you're help Jeremy,

I have also try to lift the break pedal a littel, but it give no responce,, (when the vacuum is leaking a littel bit then go the speed a littel bit down before the CC is stop), but in my case the CC is stop working without this.
Is the CC control unit over the airbag ? if so i will need to desasampel most of the car to get it ??

Regards
Søren