I asked this question in C5 General about a month ago and no one knew the answer! So I thought I would try again. There is a positioning switch on all four (front & rear) suspension arms that connect through a link to the frame. (F45 suspension) This is not the firmness selection switch circuit, (shock valving selection) which is connected directly to the bottom of the shock. I strongly suspect, though, that this position switch does control some part of the ride control system. What is its contribution? I am assumming that it does one of the following:
#1 monitors rate of shock piston velocity change (sends to ride control
module)
#2 monitors piston height inside of the shock (sends to ride control module)
#3 changes shock valving selection (in real time) based on amount of
suspension compression
#4 all or some combination of the above?????
The reason I am so curious about this switch is that I lowered all four corners on my '98, A4, F45, coupe about an inch (on STOCK bolts and NO cut bushings) and the ride went TOTALLY to hello. I mean BAD. (ANY ride setting)
This reaction/result seems completely out of proportion to the amount of lowering. In re-examining the suspension I couldn't help but notice a signifigant change in the positioning of these sensor arms. What do you think about repositioning these arms to near their original settings. Any thoughts?

:confused: :confused: :confused: :skep: :skep:

 

Can't answer your question, but if the ride is that bad, adjusting those switches couldn't make anything much worse, right? Go for it. :thumbs:

 

From the manual:


The Electronic Suspension Control Module (ESC) module provides electronic control logic and output drive for each shock absorber solenoid. The ESC module makes decisions due to road and driving conditions based on various inputs. The ESC module receives input information by sensors that are directly connected to the ESC module or by other systems through the serial data line.

The ESC module uses these inputs in order to independently control the shock absorbers at each corner. The ESC module is located in the LH rear storage.

Electronic Suspension Position Sensors

The position sensors provide the ESC module with the body to wheel displacement input. The ESC module uses this and other inputs in order to control the position of the shock absorber solenoids. If any body or wheel motion is detected, the ESC module will determine how soft or firm each shock absorber should be to provide the best ride. The position sensors are mounted at each corner of the vehicle between the control arm and the body.

 

Good topic.

I think you are the first to uncover this ride quality issue.

If the photo posted above is the switch you are discussing, I see the arm.

Make sense to me if you lowered the car you preloaded the arm and in turn activated the switch.

So is the switch position adjustable? Can the large circular sensor in the photo have is mounting bracket slotted so you can turn that piece and un-load it? The extension does not appear to have an adjustment; can one be built similar to a motor bike gear shifter arm?

Congradulations for being in in tune with your car.

Great topic.

 

Patches: Thanks for your reply. This is a BIG help. YOU da man. I think I will experiment.


Miaugi: I think I "will" go for it!


Kenny94945: Yes, that IS the switch. The ends of the rod appear to be threaded but "not" adjustable. I'm going to have to check more carefully. However, it looks like the rod end pieces are screwed onto the rod. If so, I could substitute a longer/shorter rod to adjust the switch arm position. This would be the easiest way to try different positions.


:thumbs: :thumbs: :thumbs: :hurray:

 

Should be an interesting experiment. Be aware that the total rotation of that sensor is probably calibrated to the total travel of the shock and that alteration of the lever arm length will throw the relationship off. I think what you're looking to do is compensate for losing the full adjustability of the shocks by regaining the soft side of the valving behavior it has when the suspension has use of the full travel distance of the shocks. By lowering our F45 suspension, what we've done is force the system to use less damping capability to attenuate the same forces. By shortening that arm, you may regain the full sensitivity (rotation) of the sensor and possibly restore some of the sysem's equilibrium.

Personally, I saw no discernible degradation in ride quality after lowering my F45 coupe. But it started out very "high" in comparison to the other C5's I've lowered or seen lowered.