2003 Merc Grand Marquis air suspension too high

[sleepy hollow]

I just replaced the air shocks and compressor with Arnott brand components. They seem to be good quality. However, when I activated the system, the shocks pump full and stay full. The car is not driveable in this condition and is sitting way too high in the back.

I suspected the air level sensor on the rear axle. I removed it, brought it to the dealer where I compared the resistance across the three pins (2 at a time) on the old vs new sensor when the arm is move through it's arc. Got nearly the same readings on both old and new sensors. (about 6K Ohms) in high and low height positons and zero in the middle position.

How can I tell if the old sensor is bad? I hate to buy a part unless I know for sure it is bad. This one is $150.

I believe the soleniods are good on the rear shocks since they open for inflation. However, I need to see some deflation...

Thanks

[danielsatur]

The Load level sensor didn't turn the compressor off.
''Out of range''

See Owners manual for jacking a car up with air-springs, the switch in truck must be turned off prior to jacking up.

[sleepy hollow]

Thanks for your response, but I am not sure I follow what your post implies. I am away from home at the moment so cannot look at the manual.

The switch has been off when I replaced the shocks.

I would greatly appreciate clarification. Obviously I am not clicking with what you have written.

Thanks.

[sleepy hollow]

Ok, so I have figured out how to lower the rear of the car. Basically I just removed the air supply line to the compressor and activated the suspension via the switch in the trunk.

The compressor started puming into the air, and, since the solenoids are open, the air can escape from the air shocks. Then I reinflated the shocks "manually" using the trunk switch to a level consistent with a normal ride. The car is drivable and feels pretty good, but the air suspension is diabled.

I tried fiddling with the level sensor, but it seems to have no effect on the ride height.

So, now I know the solenoids work fine, the compressor works, and the air shocks work since they are new. No leaks anywhere in the system. All fuses and relays obviously work (based on substitution with other fuses of same ratings and visual inspection).

Can someone tell me whether there is some way to test the level sensor to assure me that it is likely the culprit here?

What else could be wrong?

Thanks.

[danielsatur]

I would consider buying a used Load level sensor from LKQX, which has a graveyard of used parts.
See AF>Lincoln>Towncar & search forum ''Air spring'' ,

Best price for new parts, see www.partsgeek.com, and www.arnottindustries.com.

[Arnott Inc.]

Check the level sensor by sitting on the rear bumper, this will trick the height sensors into thinking the vehicle needs to be levelled out. There's really only 2 common things that can go wrong with the sensors. </SPAN>

1. They short out (which usually triggers the check suspension message on the dash and the code has to be pulled to confirm where the message is coming from).


2. Or the height sensor was knocked out of position, which will get the wrong reading to the compressor causing it to overinflate the air springs.

Hope this helps.

Arnott Customer Support - 800-251-8993

[sleepy hollow]

Thanks for your response, Arnott. The problem is that the only thing that happens when I activate the RAS system is that the compressor runs and overinflates the bags. The only way I can get the bags to deflate is to disconnect the air hose at the compressor and then quickly shut down the system when it gets to a reasonable height. So the car is drivable but the suspension system is off. Your suggested test will not work as the suspension is maxed out and nothing seems to affect it.

So, unless the computer is bad or the other systems' sensors are bad (doors, speed sensors, etc. - doubtful base don behavior) then the only other moving part is the height sensor. I have been reading up on Hall-effect sensors and have come away thinking it is highly doubtful this part is bad. But how can I be sure without spending another $150 to find out? And if the sensor is not the problem, then what is the problem?

Really scratching my head on this one...

[danielsatur]

The sensor isn't doing it's job, or there's a stuck on relay!

Do a Google ''Ford Air suspension level sensor''

Salvage auto parts are cheap, and you can practice removal .

[sleepy hollow]

Just as an update, I found a new sensor for $100 at a discount ford parts site. Just received it and will swap out this weekend. We'll see what happens.

[sleepy hollow]

So, to close this one out, I hope:

I replaced the old ride level sensor with a brand new one yesterday.

I then reactivated the suspension system and started the engine. Good news, the suspension check light did not come on and the air pump did not either. (Previously it would only do one thing - max out the air bags making the car undrivable.) I test drove the car twice for about 5 miles each at speeds up to about 55.

Never heard the pump kick on even after shutting down the engine and walking away from the vehicle. I assume the height I manually selected was good enough. It certainly felt like it was at the right height for the month it has been driven with the air suspension disabled. The rear is still sitting where it should be as of this morning - neither collapsed nor overinflated.

So, I am very hopeful that the sensor was the problem after all. I did change the air shocks and I am glad I did as one of them was cracked and ready to leak if it was not already doing so. The other was a bit better off but age was showing for sure. The Arnott replacements are much better quality IMHO.

We'll keep an eye on it for sure, but I think this one is a wrap.

[ascorbate]

Originally Posted by sleepy hollow

Thanks for your response, Arnott. The problem is that the only thing that happens when I activate the RAS system is that the compressor runs and overinflates the bags. The only way I can get the bags to deflate is to disconnect the air hose at the compressor and then quickly shut down the system when it gets to a reasonable height. So the car is drivable but the suspension system is off. Your suggested test will not work as the suspension is maxed out and nothing seems to affect it.

So, unless the computer is bad or the other systems' sensors are bad (doors, speed sensors, etc. - doubtful base don behavior) then the only other moving part is the height sensor. I have been reading up on Hall-effect sensors and have come away thinking it is highly doubtful this part is bad. But how can I be sure without spending another $150 to find out? And if the sensor is not the problem, then what is the problem?

Really scratching my head on this one...

So I'm now experiencing this same problem... rear air suspension is sitting too high... car was fine one day, next day after driving about a mile, rear air suspension had jacked itself to its max with the result that the rear end of the car was bouncing all over the road. Drove it back home and after reading thru this forum, I disconnected the air hose at the air compressor (which is found underneath the air filter and windshield washer reservoir) while the air compressor was running... and let some high pressure air drain from the air hose running to the rear suspension of the car. So it sounds like I now need to find this "Load level sensor" in the rear... is there one or two of them... where exactly is it in the rear?

My Grand Marquis LSE is now 10 years old... this is the first problem I've had with the rear air suspension. Next, my air compressor looks pretty corroded on the outside... and I don't yet know the condition of the rear air bags but it seems like they could be near the end of their useful lives. So it might be time for a new air compressor (~$400.00), rear air bags (~$400 for two) and now maybe a load level sensor (~$150). All of this sounds pretty darn expensive versus maybe replacing the above with Monroe's "Mercury Grand Marquis Rear Air Suspension to Coil Spring Conversion Kit" which can be had for ~$200.00... any thoughts on this?