Air suspension

Tiny
MARINOPERNA
  • MEMBER
  • 2005 LINCOLN NAVIGATOR
  • 5.4L
  • V8
  • 2WD
  • AUTOMATIC
  • 125,000 MILES
Started where upon exiting the front would drop to the bumpers. For about a month I just shut the system off before shutting off the key. Worked like a champ until it did not. Intermittently the front would drop and not come back up. Only one time did the rear drop. I could hear the pump come on but nothing. Got it to raise after what I will say was a click. If I shut the suspension switch off it will usually stay level for several days. One time it dropped over the weekend this weekend it stayed up. Had the bags checked and could not find a leak. Suggestion was to replace the dryer. I replaced the whole unit with an Arnott. At the same time I read it could be the ride height sensors so replaced those too with Dorman units which I was told are OEM equivalents. Unfortunately pump comes on rear is up but front on the bumpers. Pump comes on like it should but nothing. I did not check the pump output but do feel suction on the inlet side. Seems like only a few expensive things left. The solenoids or the suspension computer. Can you advise how to check. My shop with his snap-on tool could not locate a problem. He did clear a code C1725. At that time the dash indicated no suspensions issues. Since he cleared the code now I get "check air suspension"
Thanks for any help you can offer.

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Monday, May 15th, 2017 AT 10:53 AM

8 Replies

Tiny
STEVE W.
  • EXPERT
C1725 - Air Suspension Front Pneumatic Failure

Solenoids are easy to test. Apply twelve volts to open them and if air goes in/out they are okay.
For testing you really need the DRBIII factory tool. It has all of the items in it including tests that cycle the suspension and that can read all of the factory data. Very few of the aftermarket units can do that, especially with the air suspension because it is not a real common failure item. In this case a dealer or shop that has the DRBIII would be the best thing, even if you only pay them to diagnose the system.

Dorman = OEM is like saying Rosie O'Donnel is the same in a boxing match as Mike Tyson.
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Monday, May 15th, 2017 AT 11:20 AM
Tiny
MARINOPERNA
  • MEMBER
Thank you for responding.

I will check the solenoid.

Is there another brand of ride height sensors that are reliable that you could recommend? The Ford OEM's are outrageous at $800.00 for the pair locally. Any way to bench test them as now the Truck is no longer driveable as it is on its bumpers. If I take it somewhere I would need a round trip flatbed then I am stuck for sure. Hard to find a reliable reasonable trustworthy shop that knows this stuff anywhere close to where I am.

Unfortunately now the pump too is not reliably coming on. What are the chances its the computer?

Marino
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Tuesday, May 16th, 2017 AT 11:24 AM
Tiny
STEVE W.
  • EXPERT
I would test those sensors first, I doubt that both went bad at the same time. I would suspect the wiring or the VDM. The best way to test it is with the proper scan tool.

I misspoke about that tool though, It is not the DRBII for the Ford/Lincoln/Mercury line, Had a different vehicle on my mind, Sorry. F/L/M uses the IDS tool.

The scan tool can make the VDM enter a self test mode where it tests the sensors and itself.

To test the sensors on the vehicle you will need a multi-meter and either some back probe pins (dressmaker T pins work good for this) or some insulation piercing probes (just seal the tiny hole with some liquid electrical tape)

Disconnect the actuator levers from the arm. You will be moving the sensor arm itself. Remove fuse 111 (powers the compressor, you do not want the thing to suddenly pop into the air while you work on it)

Pick a sensor. Both sides use the same colors for ground and power. Ground is a black wire with a pink stripe and power is the red wire with a black stripe.
The left side uses a pink wire with a black stripe as the signal wire, the right side uses a Tan wire.

On the ground wires you should see no voltage when the system is on.
On the power wires there should be a constant five volts.

When you test the signal wires, connect one side of the meter to ground and the other to the wire. As you move the sensor arm the voltage should smoothly increase and decrease from about.50 volts to about 4.5 volts.

If you lack the power signal verify that fuse 30 and fuse 27 are OK. If they are then locate the VDM and test the same colors there, That way you can find out if it's a broken wire between the VDM and the sensors.
If you lack the ground side check the ground connection for the VDM, it is behind the left kick panel in the drivers foot-well. Check it at the VDM as well.

If the sensors test okay re-connect the arms and move to the air solenoids.

These are nothing but simple coils. The black wire grounds the front ones at the right side of the radiator (where the compressor also grounds so maybe check that first as rust/broken wires could be causing both issues) and the other wire powers them. To test them, unplug them and simply run a pair of jumper wires down and touch the terminals on the solenoids. Do not hold the wires on them, you are just testing them, a quick click should mean they are Okay.

If they test okay re-connect them and move to the compressor relay, From it you can test the compressor. Plug fuse 111 back in. Check the relay, it should have twelve volts at the light blue with pink stripe, ground at the black wire. The gray wire with a red stripe carries power to the compressor. The dark blue with yellow stripe is the on/off signal from the VDM. If you apply twelve volts to the gray wire with red stripe the compressor should engage and pump air.

You have now tested every part but the VDM, Hopefully you found the bad ground or power connection causing the problem. Otherwise you will need to get to a dealer and see if they can scan and test the VDM.
The wiring diagram might help.
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Tuesday, May 16th, 2017 AT 3:58 PM
Tiny
MARINOPERNA
  • MEMBER
Thank you for this second note. I will test as you say. I would like to bench test the original sensors but dont have a 5 volt power source. Any damage using a 12volt battery? If not what should the new values be?

I would certainly consider a donation but see you only do cards. Any way to send by paypal or maybe a check by post as your kindness is appreciated
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Wednesday, May 17th, 2017 AT 7:21 AM
Tiny
STEVE W.
  • EXPERT
I wouldn't use 12 volts. They are a simple position sensor and 12 volts might burn the actual potentiometer. 3 common 1.5 volt D/C/AA batteries in series would give you a 4.5 volt source. That should work for testing. What you are looking for is a smooth rise/drop in voltage as you move the arm.
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Wednesday, May 17th, 2017 AT 10:44 AM
Tiny
MARINOPERNA
  • MEMBER
Good thinking. Great Idea. Thanks
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Wednesday, May 17th, 2017 AT 11:56 AM
Tiny
MARINOPERNA
  • MEMBER
I want to test my originals. It's together and back on the ground with the Dormans. Not sure if a potentiometer is polarity sensity. If looking at the podded side would you know if the positive on the right or left?
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Wednesday, May 17th, 2017 AT 12:19 PM
Tiny
STEVE W.
  • EXPERT
Look at the connector on one on the truck, then the wiring diagram to tell which pin is power in. I would say you could do a resistance check as well but I don't see the specs for good/bad
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Wednesday, May 17th, 2017 AT 4:46 PM

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