AHC Damping Force Accuator Accumulator Replacement

Joined
Jan 12, 2004
Messages
1,322
Location
Central Virginia
 
 
 
OK. Got the front to 6.9. Helped a bit. Finally check the air pressure on my new tires. It was 50 psi all around. Dialed it back 29 front and 32 rear and everthing is much better. No wonder it felt like I was riding on bricks.
 
Joined
Jan 12, 2004
Messages
1,322
Location
Central Virginia
 
 
 
OK. GDI. After sitting overnight it now rides like it has no suspension travel at all. WTF? Others have posted with similar issues. New globes, pressure is in spec and the thing rides like a go cart. AHHH. Every small bump is felt in my teeth. Big bumps have some give. Any thoughts appreciated.

I've got some bank and might just buy a 570, but not if it will end up riding like this.
 
Joined
Sep 27, 2007
Messages
1,760
Location
Charlotte NC or ACT area Australia
 
 
If damping was good, it sat overnight then went bad I'm thinking maybe you have a low battery and the gen signal isn't sufficient to tell the AHC ecu it needs to turn on - maybe - or you could have a gut full of air still in the system. I'm leaning toward things that maybe temp related.
It would be good to know pressures and heights, did you reset the height sensor? Drive with Techstream on and monitor the damping steps?
Check for DTCs and do the 16 step test and lock it in position 1, softest, and go for a drive. That should tell you if it's a hydraulic/mechanical issue or electronic. The more relevant system data you can provide the better, it's easier then to eliminate what's not defective.
Did you do anything to the vehicle between when AHC/AVS was ok then not ok?
 
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Joined
Jan 12, 2004
Messages
1,322
Location
Central Virginia
 
 
 
Thanks, Paddo. I will did back into it this weekend. It does seem to ride more harshly when temps are lower. I have no DTCs. When I drive with Techstream, the steps vary from 4 to 12, best I could see while being safe. It is driving me nuts.
 
Joined
Sep 27, 2007
Messages
1,760
Location
Charlotte NC or ACT area Australia
 
 
FWIW my damper steps vary between 1s and 12s with the comfort switch in mid position. Might be something there? Agree it is difficult to watch the response and be safe at the same time.
It could be worth opening up and cleaning the ceramic contact tracks in your height sensors and confirming there is no corrosion and the pot wiper arms are intact as they have tiny contact fingers. Rationale here is that not only do the height sensors detect height (duh) for L, N & H they also provide the only road force feedback to the ecu by way of measuring the height differences between the UCA and chassis. There is no feedback from the accelerometers that tells the ecu the road is rough and damping needs to be adjusted accordingly - just the +/- proportional voltages from the height sensors. If they are worn (and the sliders rub constantly in a small range on the tracks) it's very conceivable that the feedback signals to the ecu could be noisy and out of range when in motion.
As a young fella maintaining naval gun and missile hydraulic servo systems if we observed $hitty dynamic responses one of the first things checked were the feedback potentiometers. That's all our height sensors are, feedback potentiometers.
 
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