I am getting ready to convert the rear coil spring suspension to Air. I have a few questions perhaps someone who has gone from Air to coil might be able to answer.

First, short of the airbags what other hardware is involved in mounting in place, ie brackets, retainers or whatever,
Second, Are the factory air line 1/4 inch? or what.

All comments and suggestions are welcome (short of telling me i'm nuts for doing this, yes I know this but I just love the way the H2 rides with air suspension)

 

I'm not aware of anyone that has converted to the air suspension although I'm sure someone somewhere has.

I believe the air lines are metric if I remember right (close to 1/4 but not exactly). I ended up replacing the lines from the compressor to the springs on mine and I ordered factory lines since they are pre-bent and whatnot to fit perfect. A couple of the lines on the compressor shelf itself are larger (close to 3/8).

What would be required....
Complete compressor shelf
Wiring harness for the compressor shelf which goes quite a few places. It ties into the BCM, has wires to the rear accessory inflator switch, wires to the ride height sensors, wires to the dash ride height button, and wires to the main relay in the firewall under the brake booster. I'm not aware of anything else that would be tied in.
Rear accessory inflator switch and valve.
Dash ride height button.
Ride height sensors for each side.
I think there is also a yaw sensor that is mounted underneath somewhere that ties in.
The air springs themselves of course.
The centering pucks that go under the air springs. The air springs themselves are centered in the axle with a plastic cup that is about 2 inches tall, considerably taller than what coil springs use but roughly the same diameter. This is a sold out listing for them - https://www.ebay.com/itm/391506668108

If your was originally air ride then I'd think it should be fairly straightforward as long as you can source whatever is missing as the wiring harness (and some other bits should already be in place). If not and the factory still installs the harness then probably still not terrible to do. If there is no harness, it will be a pretty big undertaking to set it up like factory. If the wiring is there, then once everything is installed it should just work although you will likely need access to a Tech2 to do a ride height calibration.

That being said. If there is no harness you could still install factory air springs, a compressor, and a manual control from Air Lift or something comparable and get the main functionality. With aftermarket to an extent you can also add an air tank for near instant height adjustment, add air horns, and a much faster accessory inflator. The main key is that these have factory style air springs readily available so no engineering of the suspension or mounting of them is needed which is pretty big. I have a custom built 83 S10 flatbed tow truck with Air Lift brand air springs in the rear. Works great and is easy to use.

For looking up original part numbers which are often obscure and hard to find check this site - https://nemigaparts.com/cat_spares/epc/hummer/

Good luck!

 

Wow you are the only person I've ever met that has a Solar flare orange hummer as well. It has to be one of the rarest colors.

Anyway. I hate to be that guy, but I honestly don't think air ride is better. Especially when you consider the reliability problems. But you can get a really cushy ride with coils and a nice set of shocks tuned for comfort. The only reason I would consider doing this is for towing, But even then, like MixMan said, an aftermarket air bag system is the way to go and generally more reliable, and parts would be more readily available. Definitely don't do aftermarket bags unless you're towing though. My dad had them on his f250 and because you always have to keep some air in them, it made the ride slightly harsher. Future parts availability and unreliability would drive me away from it buy hey, fun project i guess.

Like the MixMan said, if you're h2 previously had it and it was deleted, it will be much easier, however if it came from the factory with coils, I wouldn't even attempt IMO. The wiring would be a nightmare. Im not sure if the BCM would even recognize it if it didn't come that way from factory.

Good luck to you sir, and please keep us updated. This is one for the books for sure!

 

Being totally honest I have owned an 05 with coils, and 06 with Air and now the 08 with coils I am sure there are many that would say there is no difference in the ride but my butt (and my wife who surprised me) can notice the difference. When I bought my 08 and was driving it home she pointed out the older 06 seemed to have a better ride. With that said here are my 2 driving forces for wanting to do this, One, I can get the rake get all of the forward rake out of the vehicle and have it ride flat without having to almost totally collapse one of the spring coils which kills the weight handling ability of the SUT. I also have no want to crank on the torsion bars to level the vehicle. Second, I can also tow my travel trailer and adjust the rear ride height when needed.

MixmanSC is right on about the nightmare this will be trying to install the factory system . I checked with a number of junk yards, none will even consider trying to remove the original wiring harnesses even though I was willing to pay for it. They simply remove the compressor/shelf and trash the rest.

I think the best solution is what MixmanSC suggested and the end of his post and I will pursue that. I think I should be able to pick up a couple of new factory bags and the mounting assembly. A firestone compressor with small storage tank and a pressure egulator. I think the hardest part will be trying find some kind of metric (thank you Carter) to US line adapter unless the fitting on the top of the bags would accept a non metric air line connection part. I will look for a used compressor shelf or simply fabricate one and mount the compressor/hardware there.

Actually, once I get this all figured out I think I will post it up on the forum as this would also be a great solution for those with air suspension having issues with the factory components.

 

Give me a bit and I'll see if I can find the spare air spring I had from when I replaced mine. I want to think I've read of someone using 1/4" air line on them before. I have some 1/4" air line and I can test to see if it will fit without leaking or anything.

 

Excellent comments by MixManSC there's more to it than meets the eye.

The pneumatic pipes are metric, 6mm for the bags + inflator and 8mm for the 2-air intakes (which may also be needed) tried a 1/4" pipe into a 6mm fitting but it wouldn't fit, 6mm + 8mm pipe and fittings are readily available in the US.

There's also the AS Relay mounted under the hood, it's coil is driven from BCU C1-13 but it's 0V goes all the way to AS 16-Way Connector C451 Pin-M (the AS-ECU monitors the coils current) The AS Relay contacts connect to VSES/ECAS Fuse and AS 2-Way Connector C450-A.

Is the Yaw Sensor the the same as the Longitudinal Sensor / Accelerometer ? (all new to me) certainly the only sensor inputs to the AS-ECU are the 2 ride-height ones, that's not to say it's not handled elsewhere that is.

H2-SUT it may be possible to retro fit all the necessary wiring, if you need any details such as the Delphi / Aptina connectors (available) , connections etc let me know and I'll help where I can, as I'm sure other will.

Not sure what's harder, adding in what is known or adding the unknown, presumably there will be parts required by both systems, some features lost and some gained depending on the kit.

Hope it is just a case of returning your truck to how it was...

 

1/4" & 6mm requires fitting modification, 5/16" & 8mm only needs a slick lube.

 

Yes, as Ocean mentioned, the 1/4" tube did not really fit in the 6mm air spring fitting. Goes in but would not be secure as the diameter is just a bit too small to be workable.

 

That sounds like a very interesting project.. I have AIr Ride in My 2009 Lux SUV. I love it... Anyway..here's some of the problems I had. Use to Off road alot with "Club Hummer Off Road" After many times of doing that and jacking the rear height up to max this left the air bags exposed to dirt and sand which got into the lower bag support and when the rig was lowered to standard ride height for the ride home the bag was chafing on the grit between the bag and mount.

This lead to a Bag failure .....a slow air leak and both bags were replaced under warranty....The other problem was a Bad Ride sensor on the rear trailing arm which caused the rig to be lopsided.

Any way I see a loot of sub parts and equip to add to give your rig factory air ride. What I would suggest is some kind of complete aftermarket system designed for your rig.. Might be a hole lot easier... Good luck with your project.

Here's a place I found on the web at random... Not sure if it's factory or aftermarket.. Give them a call ..

https://www.sdtrucksprings.com/suspe...ir-bags/hummer

 

The H2 AS system has some safety features worth mentioning:-

• The 2" extended ride-height automatically de-activates at 40mph and cannot be engaged over that speed. Also it can only be engaged with the engine running, and the doors closed. Presumably at high speeds the 2" lift could be stability issue?
• Critical faults with the AS control system will cause an "Service Air Suspension" warning alert, such as:-
  • Ride-Height sensor over-current, and positional errors.
  • Inlet valves over-current.
  • Exhaust valve and AS Relay over current.
  • Excessive compressor activity.
  • Compressor over temperature.
  • Air pressure sensor problems.
  • Loss of stored height calibration (EEPROM Checksum error)
  • ECU configuration errors.
  • Suspension control select switch malfunction.
• The ECU monitors the 12V battery supply, no doubt it has safeguards to limit AS activity if this voltage is out-of-limits (but I know of no DTC for that condition)
• Though not directly safety critical, the ECU monitors and requires the "Engine Running" 12V line to energise the Tire Inflator and Extended Ride-Height switches and lamps.

GM did a pretty good job of controlling the AS, the sophistication of the ECU itself is very often underestimated.

Yes it can be a real pain when things go wrong, however the rear suspension has to be a critical safety system?

The Tech2 Scan Tool provides access to lot of useful diagnostic data, such as air pressure, height values, sensor currents etc, an can also be used to recalibrate the ride-height.

It would be worth knowing if aftermarket systems tie-in with the BCM or are they independent and stand-alone?