Rear Suspension Questions

[TomO]

I have a '97 Aero HHP w/ rear air suspension. I've been storing it because I have too many vehicles to drive at the moment. I start it every two weeks.

Some time ago, the rear air suspension deflated and will not re-inflate. The dashboard has a message that says "check rear air suspension"

I have a manual but all it says about the rear air suspension is that servicing or repairing it is beyond the capabilities of the average mechanic, and that it should be taken to a dealership for servicing.

I don't have any experience with this type of suspension. I have checked the fuse and relay and they are good.

What would be some things to check? I was thinking that I should check to see whether the air compressor is getting power, but I can't even locate the compressor. Where is it?

My mechanic also could not figure out what was wrong with the air suspension when I had the car in the shop recently to have the fuel pump replaced.

He suggested replacing the air bags with steel coil springs.

I have an '89 box with heavy duty suspension (it has the towing and handling packages), that I'm thinking of scrapping because it's high mileage and the water pump just went out for the 4th time in 8 years.

Are the rear springs from the '89 interchangeable with the '97? What is involved in changing out the springs? Thanks for any help/advice you can provide.

[jaywish]

If the bat is charged. Get in, close the door, open the window, turn the key to run, don't start it. Listen, first you should hear the fuel pump kick in for few moments then the compressor should start pumping.

The pump is in the left front corner of the engine compartment.

[IPreferDIY]

I'm not sure about the setup before 1998, but you might be lucky and find that the ride height sensor became disconnected mechanically. If it's just hanging there but still plugged in, it might be telling the system that the ass end is too high.

If there was a leak, the compressor would keep running to compensate, putting it at risk of burning itself out. How do the bottom of the air springs look? When they go bad, they typically develop cracks at the bottom that cause leaks.

Coil conversion is the route typically taken by people who don't understand the air suspension system, which isn't all that complex once you get to know it. If you really want to go the coil conversion route, taking the air springs out and putting coil springs in their place is pretty easy. They use the same mounting setup.

[gadget73]

The light will tend to come on if the compressor runs for too long and doesn't air anything up. Leaks in the springs or at the connections do this. If its on immediately, usually that means the switch is off or something is faulty. Fuse blown maybe.

Honestly the air suspension is not very complicated to work on. Its been made into a much scarier boogeyman than it has a right to be. The standard "put coil springs on it" response is usually the answer you get when people don't understand it. I'd get a factory service manual and use that for troubleshooting. Its not that hard, and the manuals are very good. Non-Ford manuals say OMG scary stuffs! and abandon you to fear, misinformation, or huge repair bills.

The compressor should live under your air cleaner assembly.

[His Royal Ghostliness]

I'm with these guys - door closed, window rolled down, reach in and turn ignition on then walk up to the front left corner of the car and listen for the air compressor whirring under the air cleaner box. If she runs start chasing air leaks, if she's silent check compressor wires for damage (fawkin mice!) then move to the back of the car and inspect the height sensor.

Honestly I think that air ride is pretty darn awesome, all my shit is slowly getting converted to at least partial air ride, trailer included! I'd manual-control a factory Panther air system before I convert it to coils...

[gadget73]

There is a relay for the air compressor motor too. Not entirely certain where it lives, but if its gone dead it won't run and it will probably spit an error out.

Soapy water is your friend for leak chasing.

[TomO]

The "check air suspension" light comes on immediately and stays on. I don't hear anything when I turn the key on, but before I had no idea where the compressor was. Now that I know, I will check to see it if runs.

I saw a vid on youtube that said if your air compressor does not run, you can try unplugging the electrical connector and plugging it back in, which may cause it to start working, but most likely it will stop working shortly, which means the connector needs replacing.

I would really like to keep the air suspension in the car if I can. Thanks for your help.

[TomO]

The "check air suspension" light comes on immediately and stays on. I don't hear anything when I turn the key on, but before I had no idea where the compressor was. Now that I know, I will check to see it if runs.

I was wrong about this. What happens is as follows. As soon as ignition is turned on, the seat belt chime sounds, as soon as seat belt chime stops, "check air suspension" light flashes 5 times, then comes on a 6th time and stays on. I'm not sure if this sequence of flashes has any significance, but if anyone knows, please let me know.

Also, I noticed something I hadn't seen before -- when double checking to see if the suspension switch was turned on in the trunk I saw that the harness branches. One branch leads to the air suspension on/off switch and the other branch leads to a large connector that's not connected to anything. I wonder if this could be some sort of test port or something.

Also, I looked for the air compressor and I'm guessing that when you crawl under the front driver side and look up you can't actually see the compressor because it's behind some sort of black plastic cover of some sort. I didn't see any obvious way to remove this cover. How do you get access to the pump? Do you remove the air cleaner and access the pump from above, or do you somehow remove the lower cover and access the pump from below? Thanks.

I almost forgot to mention this -- the pump does not come on and has not come on since this trouble with the deflated rear springs started.

[IPreferDIY]

... Also, I looked for the air compressor and I'm guessing that when you crawl under the front driver side and look up you can't actually see the compressor because it's behind some sort of black plastic cover of some sort. I didn't see any obvious way to remove this cover. How do you get access to the pump? Do you remove the air cleaner and access the pump from above, or do you somehow remove the lower cover and access the pump from below? Thanks. ...

I found this Arnott video for you but haven't watched it yet:

[TomO]

I found this Arnott video for you but haven't watched it yet:

That's a very good video -- thanks for finding and posting it. Will come in very handy if it turns out I need to replace the pump. Now, if I could only figure out exactly why the system isn't working . . .

[His Royal Ghostliness]

The empty connectors is indeed a test port IIRC.

I'll be of no help on the air pump, maybe someone else knows. But once you gain access to it you may be able to add air to the springs manually, there should be a "tire" valve on the thing that you can use for that.

[gadget73]

It has to be in fill mode for that to work. If the solenoids aren't open, the air won't go anyplace. There is probably a way to force that with the diag connector, but I don't know how. The only time I've done it is when the compressor was already running if I wanted to get it going faster. Did that on the Mark VII when the front suspension got rebuilt so it didn't have to spend eternity trying to pick itself off the ground.

[TomO]

The empty connectors is indeed a test port IIRC.

So, would this test port be for the air suspension system itself, where it could possibly tell me whats wrong with it? What is IIRC? Is that the test protocol like OBD?

[sly]

IIRC = If I remember correctly.

[TomO]

IIRC = If I remember correctly.

LOL!! OK, thanks.

By the way, does anyone know if the air pump on the '97 would be interchangeable with the air pump from an '89 box with the factory air shocks? I have one from my old '89 and I know it works so maybe I could try swapping them out just to see if it's the air pump in the '97 that's bad.