The rear of my car is too high and the "Check Suspension" light comes on after approx. 45 seconds
Excessive moisture is a pretty common problem for Town Car and Mark VIII(8) owners. Excessive moisture in an air suspension system is extremely hard on compressors. One of the first things to go on a compressor is the vent solenoid. The reason for this is that whenever the vehicle vents(lowers), moisture is blown through the compressor, through the head of the compressor, through the vent solenoid, and then to the atmosphere. In a nutshell, the compressor is taking a bath everytime the car vents.
WHAT IS THE VENT SOLENOID?
The vent solenoid is basically just a little metal piston that goes up and down with a coil wrapped around it. When its subjected to moisture frequently, rust and corrosion will soon begin and get worse as time goes on. When the rust & corrosion gets bad enough, the coil won't be strong enough to move the metal piston any longer and becomes inoperative either in the open or closed position.
If it freezes up in the closed position, the vehicle cannot vent the air in the air springs like the module wants it to. The result is a higher than normal rear height and a check suspension light on.
The module is programmed to try and vent the air out of the air springs within 45 seconds, but if it doesn't accomplish this goal, it will assume theres a problem, turn the light on and shut the system down. This is called the vent timeout. The system won't try to make any more adjustments until either the "ignition" is turned off, then back on, or the "suspension switch" is turned off then back on. If one of these things are done, it will then try to vent again until either it reaches the desired height or the 45 second timeout turns the system off, which ever comes first.
If it freezes up in the open position, no matter how much the compressor tries to pump, it cannot build much more than 20 p.s.i., because the compressor is simply allowing the air an easy way out instead of making it build pressure and raise the rear of the car. With this problem, if the air springs have more pressure than the compressor can put in, the springs will win the pressure battle and the air in the air springs will actually blow through the compressor and vent, which makes the rear of the car go down. You will also get a "check suspension" light on after 90 seconds or so because the module has reached its limit to raise the car.
WHAT IS NORMALLY DONE?
What is commonly done, is just replace the compressor. This will get the vehicle operating normally....temporarily. Because nothing was ever done about the moisture, it will soon overwhelm the new dryer and damage the replacement compressor.
THIS WILL HAPPEN WHETHER YOU REPLACE THE COMPRESSOR WITH A NEW OR REMAN!
To cure the root cause of the problem, you must remove the moisture from the system or protect the compressor from the moisture. The Ford shop manual says to replace both air springs, replace the compressor/dryer assembly and replace all the lines in the system. After working in Ford/Lincoln dealerships for over 15 years, I know for a fact, that this is rarely ever done. In other words, most of the techs working on the air ride systems these days aren't aware, or maybe don't even care about the moisture problem and they WILL NOT do anything about it.
WHAT SHOULD BE DONE
Since the problem is moisture, your goal is to either do what the shop manual says to do and replace EVERYTHING in the system including all the air lines, to the tune of $1,500+, OR, just replace the compressor/dryer assembly and then re-replace the dryer several times within a 6 month period. Then once a year after that. No, you wouldn't want to have to pay $300+ for a "new Ford" compressor/dryer, then turn around and spend $100+ each time for a dryer. Go HERE to get the parts for a fraction of the cost of new with a better warranty!
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