Modifying Your Air-Suspension

INTRODUCTION  
 (Back to modifications)

Have you ever wondered how the air suspension on your Mark VIII works? Have you ever wanted to be able to manually manipulate the system and adjust ride height at will? Have you ever jacked up your Mark with the air-ride switch on, only to find out that you couldn't get the jack back out from under the car when you let it back down? Better yet, do you want to SLAM your Mark? If you answered yes to any of these questions, then you have come to the right place! If you answered no, or are too scared to tamper with the system, click HERE!

This is the perfect place for people like me who love to build things, take things apart, break stuff and just overall destroy something that used to work. Ha,Ha. Actually, most of that is true, but the main challenge for designers and artists, engineers and planners is to design something that is USEFUL.(ok, maybe not artists). Being able to have usefulness and practicality are the key goals. That was my original idea when designing this system. It had to be useful and easy to operate. Further more, it had to be easy to install. Needless to say, I believe I have acheived these goals. Granted, a certain amount of expertise is required to install the system, but I do not place that knowledge and ability out of the realm of the common do it yourselfer.

The knowledge presented in the following paragraphs represents the blood, sweat, and beers that were weathered over countess months of reasearch and development. Detailed air-suspension information is only available through the factory service manuals, which might I add, are well worth the price just for the suspension information. I want to encourage anyone who performs this modification to go out and buy a service manual; not just for the information, but because you owe it to yourself to support the company from which you acquired the information. Well actually, from which I acquired the info and gave it to you. You can get them through Ebay, or at Helm Inc. I used a 1994 Service Manual, and a1993 Electrical & Vacuum Troubleshooting Manual (EVTM). The EVTM is good for describing HOW the circuit works, not just troubleshooting and schematics. It is the manual that I based almost everything in this system around. Enough BS, it's time to get started.

OVERVIEW

The following is a list of instructions for lowering a 1993 Lincoln Mark VIII. Wiring schematics and colors are the same on both 1993 and 1998 schematics I compared. To better understand the logic behind the instructions, I recommend reading the next section which explains how it works. There are also some special considerations and/or limitations to the system which MUST be read prior to installing anything. Removing the console, accessing the computer, tapping the wires, and putting it all back together should take around three hours. Fabricating the switch panel should take an hour or so. Be patient and if you are short on something, take the time to either buy more supplies or find the right tool. All modifications are done at your own risk.

HOW IT WORKS

This section will briefly explain the air-suspension on the Mark VIII. There are two air struts up front that look like conventional McPherson struts with huge airbags wrapped around them instead of springs. The rears are simply bags. There is a solenoid mounted to the top of them that allows air to pass through when opened. The solenoid opens when energized. There is also a vent solenoid in the air compressor. This solenoid must open when any vent process is initiated and it must be closed when raising the car. The custom set-up that I designed energizes these five solenoids to lower the vehicle. Not exactly rocket science. There are also three height sensors that send a voltage signal back to the air suspension computer. Additionally, there are other sensors the computer uses such as vehicle speed, braking sensors, steering, etc. The computer processes this information and uses it to make height corrections and other adjustments.

SOLENOID SYSTEM OPERATION

After completeing this modification, you will be able to press a button on your transmitter and lower the car to a desired height. When the car is started again, the stock system will sense that the car is low and start to raise the car, first the front, then the rear. If you install the necessary switches required for raising the car, you will be able to raise the car as well. This might be useful on camping trips, outdoor ventures, or just going through a car wash.

SCHEMATICS


             


TOOLS

Drill and " bit                                         Belt Sander
Jigsaw and blade                                      Phillips Screwdriver
Solderless Connector Crimping Tool        9/32 socket and drive
Small File                                                 6 inch and 3 inch extensions
Multimeter                                                Wire Stripper

 

SUPPLIES

6-Doides                                                  2 Fuse Holders and Fuses
6-SPST switches                                      Electrical Tape
30 Feet Speaker Wire                              5 Wire Splices
5 Red Female Spade Connectors              5 Yellow Female Spade Connectors
14 Red Butt Connectors                           1-6"x6" Sheet of Plastic
2 Yellow Butt Connectors                         Various Nylon Ties

It doesn't hurt to have extras!

CONSOLE REMOVAL


1) Remove the beauty cover around the radio by gently prying it loose with a flat-tip screwdriver. Be careful not to apply too much pressure and scratch the interior.
2) Using a 9/32 socket, remove the two retaining screws that hold the shifter cover in place. Once the two screws are removed, gently pull up on the panel. It will snap loose and out of its holder.
3) Remove the two screws attaching the front of the console to the instrument panel (9/32)
4) Remove the plastic cover from the bottom of the console glovebox and remove two (9/32) bolts.
5) Disconnect the wire harnesses and remove the console. Note: It is not Necessary to remove shifter lever.

ACCESSING THE AIR-SUSPENSION ECU


1) Remove trim panel covering passenger side cowl cover (kick panel). Pull up on molding to free kick panel for removal. Pull towards rear of vehicle to free the panel from it's holder.
2) Remove one phillips screws securing the white plastic wire routing cover to the vehicle.
3) Remove the five connectors attached to the white plastic cover. Using a flat-tip screwdriver, pry loose the black plastic screw to release cover. Remove two screws holding the cover in place.
4) Remove three 9/32 screws attaching passenger side lower insulator panel.
5) Using a flashlight, locate the suspension computer and dislodge the connectors. They have a latch that must be pressed on the backside of the connector. Find the appropriate wires and splice the leads to the console glovebox.


WIRING THE SYSTEM

Once you have removed the console and gained access to the EVO/Air Suspension Computer, it's time to tap the wires and route them into the console glovebox. Use extra care not to pull the wires and force one out of its connector. Make sure to mark which wires are front/rear, left/right. The speaker wire comes in handy here since they are already paired and one is striped. Keep the striped wire dedicated to either left or right for both front and rear. I placed a black piece of electrical tape near the end of the rear pair to differentiate it from the front. For the compressor vent solenoid, use a different type of wire altogether, or differentiate it in some way from the others. Once spliced, wrap electrical tape around the wire bundle as it leads to the console. This is not necessary, but it makes for a cleaner, more OEM look. You can tap into terminal 21 on the black connector for your 12v supply, or you can run a separate wire to the battery. Remember to fuse this lead, and make the fuse easily accessible. I tapped into the 8-gauge power wire running back to my amp. This allowed me to locate the fuse in the console glovebox. Now that you have the wires spliced and routed, run them through the small opening in the front (towards the dash) of the glovebox and start crimping. First the diodes, then the terminal connectors. Place a strip of electrical tape over any exposed metal leads on the diodes to ensure they don't touch one another. Plug everything in and test the system before you button 'er up. When connecting the switches, make sure you will be able to get them back off. Some of them are a tight fit. I ripped a couple of wires out of their connectors trying to unplug them from the switches. If all is well, you are past the worst, and the rest is all downhill!

FABRICATING THE SWITCH PANEL


First, make a rough cardboard template to get an idea of what you need, then trace it onto the plastic. Next, cut out a rough rendition with the jigsaw and from there use a belt sander to make minor adjustments until you get the perfect fit. Now that it fits, you're ready to prepare the holes for the switches. The eyeball will suffice, but feel free to use whatever means you feel necessary to accomplish this task. Drill five (or six*) holes and enlarge them until the switches fit snugly. This is where it helps to have switches with a lot of overlap; it makes it easier to make it look nice. That's it, you're done! That wasn't so bad after all, was it?


RAISING THE VEHICLE


To raise the vehicle, circuit 420 (pin 18 in the gray connector) must be grounded. This tells the compressor relay to turn on the compressor. To let air into the struts, open the associated solenoid(s) while the compressor is running. When the desired height is reached, close the solenoids. The stock system does the front and rear separately. I would imagine trying to do all four corners at once would create an unwelcome "strain" on the compressor. There is also a one second delay between the time when the compressor starts, to when the solenoids open. Additionally there is a circuit breaker for overload protection.

SPECIAL CONSIDERATIONS   
(BACK to OVERVIEW)


This is where I explain various aspects of the system and how they work in the real world, what to expect, what not to expect and generally warn you that you might screw something up! The first and foremost message I have is:

DISCONNECT THE BATTERY WHENEVER YOU WORK ON THE ELECTRICAL SYSTEM!

The second one is:

THE SYSTEM WAS NOT DESIGNED TO BE OPERATED LIKE THIS.
YOU WILL BE CAUSING ADDITIONAL WEAR ON ALL COMPONENTS!

While it was not designed with this in mind, that's not saying that the system can't handle it. Only time will tell. I have had this system on for over a year (wow), and nothing has "pooped out" yet. Be prepared if something does go wrong. Know how to fix your system. The parts are actually not that expensive. Arnott Industries sells front struts for $145, and the rears for $85. A compressor will run you $150 (as of 9-22-00). You can also get them through Bagmaster USA, although considerably more ($295-front, $180 rear), but less than the dealer price. The Bagmaster compressor is $215. They seem like a good company and have a message board dedicated strictly to Air-Suspension Problems, but I have noticed some of their info has been inaccurate in the past. They also were supposed to send me some information, but never did. It may have just been the associates I dealt with...( I talked to two different people, with the same results).

Now that I've said that, on to what you can expect.

Depending on the way you wire the system, the front will drop down first, then the rear. In actuality, both ends are dropping at the same time, its just that the rear takes longer because it doesn't have a 32V DOHC V8 to help it drop. This will create a jacked up look for 60 seconds or so until the rear reaches its resting place. You can control the height of the rear by adjusting the timer relay. You could wire it so that it does the rear first then the front, but that would necessitate more relays (or a different, more expensive one), and therefore extend costs. Dropping the rear, then at the right time dropping the front will essenstially make it seem like it is dropping evenly. Numerous possibilties exist with the implementation of sophistcated relay circuits, but I have not yet experimented with anything but a single DEI 528T ($25).

I designed this system primarily to be able to drop the car all the way down to "pose" on occasion. Not everyday, and for Gods sakes, not to drive it like that. Please use good judgement when implementing this modification. The main drawback to this sytem is rise time. Whenever you slam the car, it will take a good 80-90 seconds to get it back up to it's original position. You can drive it sooner only if the rear is not slammed. You just need 10-15 seconds to get some travel in the front struts. As you drive, it will pump back up. You obviously would not want to do this whenever obstacles need to be overcome. You can adjust the height of the front and rear by using multiple timer relays. One relay will suffice for adjusting the rear so that it does not lower too far.

I like to compare this modification to Nitrous Oxide injection. Why? Because if you have it, you are gonna use it. That means hardcore guys like me will be dropping the car beyond the sensor lowering height to get that extra inch of drop. That being the case, you will run into some "quirks", and they are:

1) If you activate the system while the car is running, you will recieve a check air ride message.

2) You will not be able to raise the car back up unless you turn it off, wait for 10 seconds, then turn it back on. This is assuming you did not wire the raising circuit.

3) If your car is sitting lower than the sensor height, you must turn off the air ride before you start the car to get it to stay lowered. Afterwards, if you start the car, drive down the road, then decide that you want to raise it back up, you will need to turn on the air-ride switch, then come to a complete stop for 5 seconds or so to get the computer to start raising the car.

4) If you did wire the raising circuit, it will be hard to tell how high each corner is from sitting inside the vehicle. Plus, with all the BS you must do to get it back up, you could cause an accident!

Like I said, this is for the hardcore guys like myself who always want a lower stance. Otherwise the system operates unnoticed by the air suspension system. There are also ways to get around the air ride message, but it would mean that the normal diagnostics would not register. The truth is, if you have a problem, you will know about it because the system will not operate correctly. When you have a noticeable problem you could then close a switch and return to normal diagnostics mode. I have not tampered with the Check Air Ride error correction as of yet, but gimme a few spare days of boredom and I will be hard at work killing my curiosity.

THE CURE


UPDATED 12-18-00

This page will no longer be updated here. The new link is located here. (www.markviii.org/LOD2/reservesystem.htm)

The new reserve system solves all of the problems of the solenoid mod and adds additional features.


Some links to air-ride discussion boards: Easy Street Air Suspension , Air-Ride Technologies , Sport Truck