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My SL600’s front suspension collapsed several weeks ago while driving. Initially the car wouldn’t raise at all. I had the caps in the ADS module tested, they were faulty and replaced. I reinstalled the ADS module and the car moves up and down very little. When I lock the ADS suspension, the ADS dash warning light turns on; it goes off when I unlock the ADS suspension. The front sway bar link that attaches to the height sensor was replaced with a new one. In my ownership, only the accumulators and fluid were replaced. Prior to this, ADS had been working perfectly.
STAR diagnosis gave me the following error after clearing and running the diagnostic test:
C1508
Level control blockings switch
S77/1s1.
I have tried searching for the switch part number with no success. I read a post from 2018 that stated the switch pins can lose contact.
Could this be as simple as swapping in a new switch or is there something else that needs fixing?
So the story gets interesting and hopefully better
A little backstory:
About 1 month ago, my father was driving the 600 when suddenly the car’s front end collapsed with damage to the fenders. He pulled over and the car eventually rose to normal height. This is what led me to suspect the capacitors were at fault.
The car was taken to the mechanic for repairs. The front sway bar linkage was among the parts replaced. After the car was lowered from the lift, the car collapsed while moving.
Capacitors were replaced, steering wheel turned and I have run star x2 with the only error code being the switch code.
Could the front sway bar linkage adjustment be off? If so, how would I adjust it? I assume I lock the ADS, raise the car and adjust, correct?
I’ve read that a little adjustment goes a long way.
The error message is not an error; it always indicates when the red button has been pressed. A worn sway bar link is very common, especially after some decades of work. You have to adjust it manually after replacement, and you are right: Very tiny changes in lengh makes huge differents in hights.
Potentially stupid question, but can the adjustment be made with the link already installed or should the link be removed, adjusted and reinstalled? I just want to make sure my mechanic doesn’t hurt himself or further damage the car.
The link has to be installed and the mechanic has to be VERY careful. Do not loosen the screw completely. And never lift a wheel completely off the ground with the engine running, otherwise the ADS oil will leak out of the reservoir.
So my mechanic and I jacked the car just enough to slip underneath. We adjusted it about a 1/4 inch. The car didn’t rise but the nearly full hydraulic fluid reservoir dropped to below minimum level when I activated the height switch to the top level. I foolishly forgot to bring hydraulic fluid, so I’ll top it off next week. But I feel things are going in the right direction.
The ADS II valve block actuators wiring should be checked. It can be easily checked where the valve block harness plugs into the main harness near the bottom of the radiator reservoir tank.
Unplug it and pop it open, hope it doesn't look like mine did.
If your plug looks like that, then there's no use looking at the actuator wiring itself.
I wonder if MB still sells the valve block? I rebuilt mine with one I got in trade.
Hopefully, the guys at the shop did a good job when they replaced the 2 capacitors in the ADS module.
My mechanic adjusted the link, and the car rose up!
It has a little too much oil in the reservoir, but I am just happy that it’s up.
The car had new center link, tie rods, sway bar and idler arm bushings, 99+ control arm and brakes, and engine mounts (ouch) installed up front.
Flex discs, diff and axle mounts as well as the rear control arm links were replaced as well.
I didn’t have a chance to check the ads plug, but will do so.
Who knew 2 bad caps and a improperly adjusted link could cause so much damage.
My question now is what damage has the suspension suffered from being totally collapsed?
Also how would the front strut mounts be replaced.
I am trying to overhaul suspension and drivetrain. To my knowledge, the ads shocks are original and not leaking as are the springs and I suppose shims.
My question now is what damage has the suspension suffered from being totally collapsed?
Probably no damage. There are usually additional bump stops above the piston rods, which can wear out with age and are best replaced when replacing the strut mounts.
Also how would the front strut mounts be replaced.
Oil will leak out; the replacement is ZH-M. It's best to tighten the three nuts with the car on its wheels, not with the wheels hanging on a lift. Otherwise, the slight play in the engine mount bolts in the body holes can lead to the front axle being unadjustable.
Last edited by AndreasHannover; Mar 31, 2026 at 01:10 AM.
Thank you for the part numbers. I went ahead and ordered the strut mounts (ouch!). I was able to find a pair of 99+ brembo calipers for cheap. Had them rebuilt and painted silver. Now to fix the damage from those faulty caps.
Can you visually confirm if there are any leaks? If one of the shock absorbers is faulty, it’s quite common for hydraulic fluid to escape, especially on a self-leveling suspension setup.
No, everything is standard. I had a SL60, which had different springs and a different stabilizer bar. But it also didn't have ADS and... four cylinders too few. So he had to leave
Unfortunately not, but I never actually measured it. Subjectively, I didn't notice any difference compared to a standard suspension; both lean in fast corners like a small ship in heavy seas. Not quite as much as the ADS suspension, but bumpier than ADS, though ages away from the ABC in the R230. But that's fundamentally more than just a generation more modern. Double wishbones would have been nice, but they were too expensive back then.
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