Air shocks, onboard compressor

[sgath92]

Factory auto leveling air ride hasn't worked in the time I've had my car. Guessing it developed a leak, which caused the compressor to stay on all the time, cooked the compressor. Factory shocks seem to operate up to 150psi, gabriel "hijackers" go up to 200psi so I wanted to put together something cheap & simple that could handle that if I ever needed them in the future. Cheapest on board compressor I could find aftermarket that is rated for 200psi is the Viair 380C, so I got one of those. Then I had to find an air pressure gauge, and went with the Viair 90090 [0-220psi, 2" black face single needle]. Just about all the other air pressure gauges I was finding only went to like 100psi.

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Hardest part was finding the right compression fittings. Factory shocks use 1/8 hose, and the fittings/hardware used from the factory is cheap push together plastic stuff that really does not inspire any kind of confidence. For now I am going to cut the 1/4 hose off the back of the manual fill valve, put a 1/4 NPT compression fitting on it and plumb it in that way. If the plastic factory fittings & 1/8 hose end up leaking badly I will have to go get NPT compression fittings for them. Don't want to do that, because it seems like no one uses NPT fittings for 1/8" airline so they're a bit pricier.

Electrically I am just going to use a SPST to trigger a relay to control the compressor. This will assume that anyone who ever puts air in the car knows what they're doing and watches the needle on the gauge to turn the compressor off when it reaches the appropriate psi. Already needed to mount a SPST for the reverse camera [its not wired to the reverse light like it "should" be] so I made a quick bracket:



Bolts into where the ash tray would go and is completely reversible. Forgot that this gets rid of the cig lighter socket, so I will wire one up in the glovebox in case I ever need to plug something in [that's where the USB port for the radio is anyway].



Doesn't look too bad. Still need to run a 2-4 ga cable to the compressor under the table, wire up the relay, mount the compressor under there. I've only run the hose for the gauge so far, still waiting on the 1/8 NPT male for 1/4 hose compression fitting.

Do I really need to have an air release solenoid? I have a hard time imagining why I'd want to let air out of the system intentionally.

Might eliminate the hose on the right of my diagram, fitting EDD-166440 & one of the 92837 fittings and simply screw the T fitting directly into the air compressor. Part No. 92842 is simply an adapter so that if I ever go to a bigger air compressor I don't have to change much.

I like the viair fittings, since they're two piece fittings where the hose slips over a nipple & then the bolt clamps down on it. I really don't care for those disk-shaped "crush" 3-piece compression fittings and always seem to destroy the first crush disk and need to go buy more. Someone should tell the engineers at AutoMeter about that. A tool to make it easier to slide hose or line over nipple fittings would be nice too, but google says there is no such thing?

[hotroddwayne]

Load leveling systems can be a complicated mess. I've converted 2 of my hearses to a manual fill, since the compressors are usually DOA but the shocks are fine. Typically the original shocks have 2 lines each, a switch to activate the pump, running through a dump valve and a manifold... then a single line to the compressor itself. I cut the single line from the compressor, unplug it's power source, and buy an "air shock line kit" for it's fill valve, o-rings, and fittings. You cap one side of the fill valve and run your single line into the other side and mount it where you can easily access it with your garage compressor and fill or deflate the system to whatever height/stiffness you want with an air valve just like "back in the day" with Hijackers air shocks...

[sgath92]

Well I'm about 95% done with this project now. Everything is assembled & working, just need to go through and use adel clamps to clean up how the hoses & wires are run. Ended up just attaching the airline "T" to the air compressor to eliminate some hose & fittings [less joints = less possible places for leaks to start?]. Getting the battery cable & airlines to the compressor under the table was tricky. I guess to make the compartment under the table flat & square, they laid down a false floor of 1" plywood which covers up the area where the 2nd row seat passenger's feet would rest. So there's like 4+ inches of empty unused space above the sheet metal there. I ran a 4 AWG cable from the battery through the firewall under the front seat and into the table's compartment. But since there is no sheet metal accessible from inside that compartment I ran a different length of 4 AWG threw the wood & bolt to the sheet metal below [to supply the ground connection].

12 AWG goes off the end of those battery cables to the compressor, my ac power inverter, and the relay for the compressor. Both the compressor & the ac inverter are on separate 30amp inline fuses.



AC inverter is not staying there, not sure where under the table I am going to end up bolting it down. Considering screwing it into the underside of the table since that 1" ply should give me enough length to use wood screws w/out poking threw the table. Red cable coming out of the floor in front of the inverter is the 4 AWG ground. Still plenty of room in there, would not be difficult to hide an air tank & some solenoids in there if I ever got ambitious enough to try to bag the car.

Not that impressed with the viair gauge. Needle is very jumpy while the compressor is running. In order to get an accurate reading I have to flick the compressor off for the needle to stabilize. But, there aren't a lot of alternatives in 0-200+ psi in-dash air gauges. Maybe they assumed most people would be using air switches to automate their air systems?

[BIGEVIL]

Needle is very jumpy while the compressor is running

I think they all do that. I used the master lift kit for my air shocks.

http://www.suspensionconnection.com/cgi-bin/suscon/25592-load-controller.html

Even with that tiny compressor, the air gauge flutters while inflating.

On a side note, some how my compressor did not shut off while on a cruise and it ran over 200 psi before I saw it and unplugged the switch. Fortunately nothing bad happened. I have yet to duplicate the problem.

[sgath92]

I think that's how come these compressors end up fried on so many OEM applications. A leak develops or the pressure switch being used to control the compressor doesn't ever engage so the compressor just keeps running until it dies. They're not meant to run for hours & hours nonstop. Supposedly the viair brand compressors have something internal that overrides them to turn off if they overheat, but I don't think the factory GM ones had anything like that.

I had a simialr problem when the internal mechanism of the power antenna wore out. The motor would just sit there running nonstop whenever the car was off. Kept draining my battery until I realized what was going on. Should have had something designed to realize "its been X minutes so if it hasn't worked yet, it won't" and overriden the motor. But I guess that would have cost more money for a problem that won't occur while the car's still new enough to be under warranty.