More information on my issue.
I have been having an error where no DTCs are set but when monitoring my I930 signals when driving the PID Damper Firm error =YES. All shocks are firm. Level is fine. Compressor works as it should. I decided to OHM out the switching solenoids on each shock. ( the solenoids that control soft and firm) Testing the front ones a measure 5.4 ohms on both front shock. The rear ones measure 2.4 ohms on both. Is this correct? I thought they should all measure 5.4 ohms.

 

New news to me, and 'just in time'. Hope to pull one if not both rears tomorrow. Will check both DC resistance in Ohms, annnnnd .. inductance in fractional Henrys ......once I have access in the boot.

Not that it has the same utility for my needs, given my replacement struts have no solenod modulated valving.

All I need the info for is to select appropriate "cheater shunt" resistance (and Wattage..) values to prevent error messages arising.

 

That would sure be nice to know since no one seems to know the real answer.

 

The OEM Bilstein will be whatever it is, DC Ohms or AC/Pulsed Inductance.
I'll post both values once I'm into the wiring.

Resistors meant to be here Saturday should arrive Monday evening. Not planning to cut into the wiring until I'm ready to connect those.

That said, I THINK both resistance and inductance annnnnnnd 'workable' values for 'cheater' resistors as well... HAVE already been posted?

I've ordered five each in 15 Ohm and another five in 20 Ohm, 'will adjust' if those aren't close enough.

 

Hi knowit,

I had a few minutes this evening so I measured a couple of air spring/dampers randomly selected from my collection.

The DC resistance of the front unit's ECATS solenoid is 5.3 ohms (Ω):




The inductance of the front unit's ECATS solenoid is 13.1 millihenries (mH):




The DC resistance of the rear unit's ECATS solenoid is 5.3 ohms (Ω):




The inductance of the rear unit's ECATS solenoid is 12.8 millihenries (mH):




I connected to the solenoids using an OE harness connector cut off of an X350 that I converted to Arnott coil suspension:




When you measured the resistance of your rear units, were they connected to the vehicle harness? If so, there could be some parallel resistance in the circuit that is causing your measurements to be low.

Cheers,

Don

 

Thanks so much for this info Don. Much appreciated. When I measure the resistance I did it at the connector where all the ecat solenoids plug into the ASM. The connector was disconnected from the ASM to take the circuit out of the loop. Possibly somehow I am reading through both rear ecat solenoids at the same time. That would explain the 50% resistance reading. Going to measure right at the strut next time. For all intents and purposes my suspension seems to be operating correctly except for the Damper firm error=yes. I sure would love to know what causes that error.

 

OK, so quick update on my issue. External temps DOES make a difference it seems. It's like as if some electronics somewhere needs to warm up to give correct readings. 36c external temps now = no firmness fault! Anything below 30 and it needs to warm up before it softens up! So I'm suspecting recently swapped front right shock may be faulty OR the front height sensor I bent when doing the first shock (forgot to take it apart). May have moved some of the internals enough for heat expansion to "fix" it. I'm guessing it's just a carbon track and arm type deal. I have a new OEM one on the way so we will see.

New development though. My right rear shock has started to hiss over bumps. It's not bottoming out and compressor refills it but clearly it has a leak so this may be the culprit!! I have yet another Miessler unit on order and will swap it out next week hopefully. Also likely to be the cause of my overnight sagging and maybe the firmness error. I will not install the new sensor which hasn't arrived anyway, at the same time as the shock, just in case I fix the fault, I'll want to know what fixed it!!

I will report back!

 

Well this annoyance is still ongoing. Just did my right rear shock and now the error firm YES will not go away.... It flickers from time to time but stays on. I'm beginning to suspect the front accelerometer might have been displaced when I installed that shock which is when it all started. Also noticed today that the front seems to be overinflating... If I can't fix this issue, I might have to sell and count my losses before it turns into more of a money pit.

 

For about $1000 you can convert to coils. Sell your old air shocks for cash and be done with it. I still can’t resolve my damper firm error either. Going to go coils if I have to.

 

No need for extreme measures. Car rides just fine with variable damping outright disabled.

Cutting the lead pair to a(ny) given air-strut.shock unit, terminating the vehicle/controller side with around a 15 to 20 Ohm resistor, and either of $$$$$$$$ Bilsteins or $$$ Meislers should act like $ Suncores. Air struts, not coilovers, but which have no damping modulation, Fixed valve rate shocks rather - same as coil-overs.

Suncore (Chinese) air struts are about the same cost as the "better" among the many coilovers - under $200 each corner.

Plenty of miles on a wide variety of roads already and the fixed-not-variable damping rate seems OK to me. Unlike coilovers, the Suncores still load-level like the OEM Bilstein or aftermarket Meisler air-struts do.

Not expensive to try it - given the resistors are really cheap and waaaaaay easier to cut-in than replacing with coilovers.

The cut in the leads is easily reversible. It's just ignorant Copper wire, not fibre optics. One COULD even put in a switch!

 

Thanks Bill, I'm beginning to think this has something to do with front right shock. That's where it all went wrong and yesterday, after changing rear right, I did a quick scan and found a CATS error on front right as if the shock had been disconnected. I deleted the error and it did not show up again but I re-seated the connector and went for a test drive to find firmness error now permanent! Could this connector be loose? Maybe deep inside something is off.. Would that throw my firmness error but not a code? Will do some more digging and test voltage and ohms to see what's going on but will definitely look into your option. I'm quite happy to live with a comfy ride without the dynamics, and yes, better option than giving up!! I suppose if I do one at a time and the firmness goes away, I will find the source of my problem!

 

I feel your pain.... This firm ride is annoying the crap out of me!! But Bill has posted another option which seems better than going all out coilovers and might help me figure this out. If I disconnect each shock one by one and stick in a resistor at the plug connector to avoid a CATS error, I might be able to at least start narrowing down the fault. If it's my front right shock which I suspect might be a faulty unit, I'm going to find out and I can get it exchanged under warranty. Hopefully my worse case scenario is end up running non adaptive air dampers. We will see...

 

Some other options for further 'detective work' .. if you care to chase...

I no longer have damper solenoids (400 Hz voice-coils, nearly) to 'control', but if I had wanted to do so independently of the onboard module?

ISTR other members have published the needful as a two state (ON / OFF aka PRESENT/ABSENT AND NOT otherwise modulated in rate, duty cycle, or level...) 400 Hz square-wave @ 5 VDC and 50% duty-cycle?

A very easy pulse train to generate with cheap components... if one wanted to "talk to" one damper at a time to make it soft or firm, "manually".

Keep in mind the air strut has NO inherent relationshio with the damper other than physically coaxial packaging. Their management is separate at the device level, only inter related up at the top of the Artificial IDIOT pyramid.

"Artifiicial IDIOT" because it cannot sense the present condition of the pavement, let alone 'future' by even a fraction of a millimeter, inch, a yard, klick or mile AHEAD as a human can 'see'.

Such sensors as are all it owned as-built are reacting only to events "per rigid plan" (Accelerating from stop. Braking) or as have transpired several milliseconds in the PAST (short or long patch of "washboard" pavement, etc.).

As with "self driving" vehicles, active suspension needs accurate look-ahead to be able to do more good than harm.

Absent that, I am better-served with a suspension that simply acts the same all the time. Given a stable & predictable platform, I'll do any 'adjusting' as required by environment & circumstances, thanks.

It's why they call us "drivers" instead of "boiled turnip at the wheel".

 

Bill you star! If you were closer I would send you a bottle of "Jerez". I unplugged the damper connector and shoved in a 33ohm 10w resistor (only one my local electronics shop had) and the firm error is no more!! Clearly something wrong with that damper so I should be good for a return/exchange (bought it June 6th). For now I will do the same to the front left shock so I have some balance. At least while I sort out the new damper I don't get the annoyance of firm dampers!! I'll test the damper later today when I pick up my new multimeter and post the results. Also noticed that the front did not over inflate as I have been seeing recently...

 

I'll guess simply an open-circuit in/to to the solenoid, then!

GREAT NEWS that a 33 Ohm did the do as it means:

- lower-Wattage resistors can survive

- AND there is lower drain on the control unit.., so the risk of force-failing its output driver components is reduced. THIS... is far the more important.

At least one Prior Pilgrim had posted use of TEN Ohm. At that draw, ISTR he had used 50 or 100 Watt units. I HAVE stout variable (100W) I meant to test with, but went lazy and simply ordered five each @ 15 Ohms and five @ 20 Ohms.

Vintage Volvo's used a different system to modulate their dynamic dampers. Stubborn Swedes even cut their old shocks to bits and retained the actuator coil for a dummy load! Our ones are too dangerous to disassemble, but the coil isn't very large.

Wonder if they got the idea from making winter clothing out of animal hides - retaining claws, teeth, and tail?

Picture it. Stone age:

"Learn this well, Son. Pass it on. Some day one of our descendents will need to fix a badly engineered motorcar!"

"Right Dad. But what does one do when a woman is angry with you?"

"Beyond our ken, son. Work on stuff we can actually MANAGE.
Sharper stone tools. More durable footwear. "Metal" to replace stone. Motorcars. SAAB fighter jets. Cell phones. Space travel.

 

I've ordered the 20 ohm resistors as I'm seeing a long battle with Autodoc for the exchange part under guarantee and do not want to overload anything!! They have requested a foto of the damage...... Hilarious. Sure, I'll just chop up the damper and show you the electronics shall I? This after explaining how I came to discover the fault. I've also just tested resistance in that damper and guess what? No resistance.... zero, nada! So I'm sending them a picture of that!!

 

E=IR. I = E/R, R = E/I.....Ohm's 'Law". For a(ny) given Voltage, the higher the resistance, the lower the current as will flow AKA the lower the energy and HEAT load imposed on the driver circuitry..

33 Ohms loads less than 20 Ohms ... 15... 10... or the nominal 5 & a bit the coil "presents itself as" ....for DC resistance.

IOW stick with 33 Ohms if it works. We might have to go through a cold winter to be sure it is Goldilocks-good, but BFD. I'll be ordering some 27, 30, 33 Ohm resistors.

As it is ACTUALLY an inductor being operated off of a square-wave (form of AC) the 20 or 30-odd Ohm resistance seems to be about right for a PASSIVE lumped-resistance making the driver circuit think it is reaching the REACTIVE inductance of the no longer present solenoid coil. It has no other means of sensing the driven element presence or level of activity besides monitoring the effect of current drawn.

Nah. 'Scope trace and/or meter display. "LCR" meters are no longer costly or bulky. I acquired a newer, lighter, cheaper "Proster BM4070" specifically for this challenge. No USB data-out as the 'scopes have, but it has a "DH" (Display Hold) feature. A(ny) camera does the rest.

LOL!

As said "open circuit"

Between the service person's ears as well as the damper solenoid circuit!!!

 

Ah! Gotit thanks (I guess it's a tell me you know little about electronics without telling me moment lol) I'll keep the 20's close by and see how things turn out this winter, albeit mild that they are in southern Spain!

 

First trip to Cantabria, scouting for a nice place to retire.. had taken a really cheap flight out of London to Bilbao, picked up a rental car, headed for Santander.

Temps long the route, midnight to 2 AM, 16 February, were running 17 to 21 C. Successive trips, I found summers not overly hot, and I liked all four seasons right on the coast or just a tad inland & upland.

Costa Verde is amazingly "temperate" year-round. Cheaper than Lugano/Campione as well.

South of Spain? T'was interesting to visit, but I wuddn' wanna try to LIVE there..

 

Hot summers makes the southwest a turnoff with temps hitting 38c at times, it's a price to pay for sure, but fortunately only July and August and not all the time. Maybe a few days or a week tops every 10 days, comes in cycles with reprieve and then pizza oven blasts... Rest of the summer 28-33 and of course mild winters and amazing spring and autumn weather. I'm a biker (MotoGP and SPBK come to Jerez every year which awesome) so riding around here can be done all year round mostly. It's cheap, relatively low population, dining out is amazing value with Michelin Guide restaurants costing 60€ a head as long as you don't go crazy on the "vino" of course, and with amazing roads with not much speed detection, I love it here but ideally I would have a house bang on the coast (about 30kms away from me) to escape the inland high temps in summer. A retirement option for sure...