Ride height with AlfaOBD (air suspension)

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Bootsy1968

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I have a 2018 Ram 2500 with rear air suspension. Does anyone know how to calibrate the sensor for the rear air suspension. Thanks

Nine leans 1/2" on the passenger side
 

Jacobsen

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I input the measurements in millimeters into the ride height setting...
I tried everythig in the alfaobd menue on suspension module and nothing helped. It can be commanded via alpha obd into off road 2 and after doing so can be switched back and fourth from off road 1 to 2 a few times but then it goes back to selected ride height unavailable due to payload error. The component air mass / pressure / ride height readings diagnostic does not work it just doesn't do anything. Not sure if it's supposed to work? Anyway these offsets look bizarre to me.

123_1.jpeg123_1(1).jpeg
 

Foefame

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I just replaced compressor and valve block. Refilled tanks with 175psi nitrogen. Now with truck sitting on all 4 bumpstops when I try to add air to bags with alpha obd nothing happens. When I do conpressor check I can hear compressor cycling. Just no air going to bags. I keep getting low air mass code and plant mode. It won't let me set ride heights with obd. I have service air suspension on dash and all adjustment button lights are flashing.
Any suggestions on a fix would be appreciated.
 

wes8398

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In the event anyone's still following this thread...
Has anyone ever plugged/pinched/capped the air INTAKE line (located behind the pass side taillight with the exhaust line)? I'd prefer to know there's a leak by NOT taking in outside air than to have to learn the hard way when the weather goes frigid and stuff starts to freeze up and go haywire. I'm thinking the compressor would try to pull, then meet resistance, then stop (hopefully) give up without doing any damage...‍♂️
 
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Roman217

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Probably not the best idea. Do a proper leak check. I have learned this lesson the hard way and spent money replacing parts that didn't need to be replaced. In my case, the leaks have been on the fittings on the tank and tank manifold. If you have AlfaOBD, use it daily to check the air mass in the air suspension, it should stay pretty consistent. The make up air routine is pretty obvious and sounds a bit like a whistle behind the tail light. You'll hear it cycle between the whistle where it pulls outside air then a slow air release to dry out the desicant beads in the drier. It will repeat these cycles until the tank is topped up. You will see vent and compressor temp related DTCs if you have a leak.

If you suspect you're losing air and hear that the compressor is pulling outside air in every few days then you need to find the leak. Grab a spray bottle pull the rear fender liner / dust shield and spray all the fittings on the valve block, back of the compressor, and the air tank. In my case, it was pretty obvious I had a leak at the fill ports and at the tanks (see pictures ). Pulling the fittings and cleaning the orings fixed it but I would recommend sucking it up and replacing the fittings even though they costs $10-20 a piece. I cleaned them and it worked until it didn't because eventually one line slipped out of the old fitting and I had a 120 mile drive home on bump stops. Buy new fittings.

Next, spray down the fittings going to each air bag and check for leaks there. From there, spray down the front struts at the base of the shock at the end of the dust boot and really just spray the whole thing down to check for bad air springs.

Finally, if there are no leaks in those places but you're still losing air, then it's most likely your rear air springs. Buy some long zip ties to replace the zip ties securing the dust boot. Raise the truck to off-road 2 then cut the zip tie to pull the dust shield down. Spray down the air spring and look for bubbles. Pull the shield up from the bottom and spray them down again.

For refills, I use an HVAC line set and an automotive cold side fitting (harbor freight). Last time I refilled the system, I vented all the air to atmosphere so the truck was on bump stops. Then I pulled a vacuum with an HF vacuum pump and let it sit a while to make sure I didn't have any leaks. Before releasing the vacuum, I dipped the hose into some air brake anti freeze and let it the air tanks suck it up when I released the vacuum. Air fill set up is in the pictures.

DO NOT and I can't stress this enough, DO NOT pour air brake anti freeze into the intake hose behind the tail light. The the external air intake flows through the drier and to the compressor. Best case you will coat the desiccant beads in oily air brake antifreeze making them useless or worse case you end up running fluid through the compressor and damaging the piston. Let the vacuum in the tank suck up a couple ounces of the air brake anti freeze, don't over do it, it's a closed system so a little bit goes a long way.

Finally to refill, fill the tanks to 175psi with nitrogen then raise the suspension to normal ride height. Keep topping off the tanks as the ride height rises to make sure it doesn't start the air make up routine and pull in outside air. Using AlfaOBD you can refill the springs one at a time using the "complete" option. Top up the tank to 175 between each fill. I found it easier to just command the suspension to normal ride height and just fill the tank as while it's raising the suspension.

At this point, you will be slightly overfilled but the system will vent the extra air. Lower it to entry / exit and you should hear it vent a couple a times. Once it settles to 170ish bar liters for the air volume, you should be good to go.

If you suspect you have some moisture but no leaks, you can drain the system and pull a vacuum to boil off the moisture then refill with the steps above.
 

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Last edited:

wes8398

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Probably not the best idea. Do a proper leak check. I have learned this lesson the hard way and spent money replacing parts that didn't need to be replaced. In my case, the leaks have been on the fittings on the tank and tank manifold. If you have AlfaOBD, use it daily to check the air mass in the air suspension, it should stay pretty consistent. The make up air routine is pretty obvious and sounds a bit like a whistle behind the tail light. You'll hear it cycle between the whistle where it pulls outside air then a slow air release to dry out the desicant beads in the drier. It will repeat these cycles until the tank is topped up. You will see vent and compressor temp related DTCs if you have a leak.

If you suspect you're losing air and hear that the compressor is pulling outside air in every few days then you need to find the leak. Grab a spray bottle pull the rear fender liner / dust shield and spray all the fittings on the valve block, back of the compressor, and the air tank. In my case, it was pretty obvious I had a leak at the fill ports and at the tanks (see pictures ). Pulling the fittings and cleaning the orings fixed it but I would recommend sucking it up and replacing the fittings even though they costs $10-20 a piece. I cleaned them and it worked until it didn't because eventually one line slipped out of the old fitting and I had a 120 mile drive home on bump stops. Buy new fittings.

Next, spray down the fittings going to each air bag and check for leaks there. From there, spray down the front struts at the base of the shock at the end of the dust boot and really just spray the whole thing down to check for bad air springs.

Finally, if there are no leaks in those places but you're still losing air, then it's most likely your rear air springs. Buy some long zip ties to replace the zip ties securing the dust boot. Raise the truck to off-road 2 then cut the zip tie to pull the dust shield down. Spray down the air spring and look for bubbles. Pull the shield up from the bottom and spray them down again.

For refills, I use an HVAC line set and an automotive cold side fitting (harbor freight). Last time I refilled the system, I vented all the air to atmosphere so the truck was on bump stops. Then I pulled a vacuum with an HF vacuum pump and let it sit a while to make sure I didn't have any leaks. Before releasing the vacuum, I dipped the hose into some air brake anti freeze and let it the air tanks suck it up when I released the vacuum. Air fill set up is in the pictures.

DO NOT and I can't stress this enough, DO NOT pour air brake anti freeze into the intake hose behind the tail light. The the external air intake flows through the drier and to the compressor. Best case you will coat the desiccant beads in oily air brake antifreeze making them useless or worse case you end up running fluid through the compressor and damaging the piston. Let the vacuum in the tank suck up a couple ounces of the air brake anti freeze, don't over do it, it's a closed system so a little bit goes a long way.

Finally to refill, fill the tanks to 175psi with nitrogen then raise the suspension to normal ride height. Keep topping off the tanks as the ride height rises to make sure it doesn't start the air make up routine and pull in outside air. Using AlfaOBD you can refill the springs one at a time using the "complete" option. Top up the tank to 175 between each fill. I found it easier to just command the suspension to normal ride height and just fill the tank as while it's raising the suspension.

At this point, you will be slightly overfilled but the system will vent the extra air. Lower it to entry / exit and you should hear it vent a couple a times. Once it settles to 170ish bar liters for the air volume, you should be good to go.

If you suspect you have some moisture but no leaks, you can drain the system and pull a vacuum to boil off the moisture then refill with the steps above.

Thanks for taking the time to post all that. It's about exactly what I did last week to get sorted. One thing I'd clarify is that you should add air to the empty airbags first by a couple "short" fills... THEN a complete fill. You risk improper seating of the air spring and also explosion (if the bladder isn't properly folded over itself) by going straight to a "complete" fill from vacuum/empty.
I found a very useful FAQ post on one of the 1500 diesel forums, as well as a whack of insights through various Google forum searches. I had been compiling information since the day I bought the truck ; knowing that it was a matter of when and not if I'd have issues with the air ride.
All said and done, I replaced my rear bags with Arnott replacements (Rock Auto had the best price by far @ ~$550) and refilled the N2 with a friendly HVAC neighbour's tools. Took a couple hours total, and honestly the most difficult part was probably just getting all 4 corners unloaded and in the air safely to do all the purge & refill stuff without a lift. I need to get myself some extended jack stands. A Quick Jack would have been MONEY, too.
One thing worth mentioning that I felt a little mislead on was the final tank pressure to expect. I just about had a fit after my first N2 refill and buttoning everything back up to see my "tank pressure" had dropped to ~8 bar (116 psi). I thought I'd missed another leak or something had gone wrong. Went and re-borrowed the N2 tank and tools, and went back through the whole procedure over again yesterday (despite a million other things I had to do), refilled to 175psi, then all the programming/checking. Started getting over-pressure errors and a system that wouldn't lower the truck. Did a "short" vent to atmosphere from each corner which dropped the air mass from 230 bar-liters to 200ish, then waited a bit. I heard the system self-vent a few more times, then commanded all the different ride heights without issue. All said and done, the tanks are back to about 8.5 bar and air mass is 170 bar-liters... guess that's just where things settle out to.
But now that I know the system is free of moisture and topped up with just N2, I'm still tempted to try blocking the intake hose. There's no reason the system should need to secretly take in outside air... and when my next leak develops, I'd like to know rather than have it masked by this make-up air routine.
 
Last edited:

Roman217

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The make up air routine will run as soon as you start the truck. It's a pretty clear low pitched whistling sound. Don't block the air intake, you're more likely to ruin the compressor and that's a more expensive fix than pulling vacuum and refilling.
 

wes8398

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The make up air routine will run as soon as you start the truck. It's a pretty clear low pitched whistling sound. Don't block the air intake, you're more likely to ruin the compressor and that's a more expensive fix than pulling vacuum and refilling.
Ugh. I want to plug it so badly, though.
I'll just continue to keep an eye on my air mass numbers and such. Thank god for alphaOBD.
 

Rebeler69

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I'm new here... Read all you posts and followed all of your instructions... But i've a real major bug in my system i have to tell you...

Everytime i go to write suspension height values, the truck levles it self to his normal height i think - so far, ok...

But in this time it is just saggimg really bad to the left in the front and rear... So it goes down more left than right... About a few inches... But i am able to lower the truck on all corners normally - till the errors come up...

Sry for my english i'm from austria...
Please help...
 
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