Air Suspension Solenoids

[shou]

I have just installed the Suncore compressor and air bags on my early '03. I cannot get the bags to fill.

The comp comes on for maybe 5 seconds and stops. After the comp runs and I haven't done anything to release pressure from the lines, it vents a burst of air before running again.

It seems the Solenoids are not energizing. When I disconnect the air line from a solenoid I get a blast if air. When I run the pump with the line disconnected air blows out. I've run the comp with the solenoid hooked up but removed from the bag and nothing comes out.

I've checked fuse 16 and relay 304. I tried to check voltage at the plug, but it appears the solenoid needs to be connected for the system to do anything. That kind of leads me to believe it's not a wiring issue since if there were an open, the system wouldn't work at all.

Initial cause for replacement of comp/bags was a rotted out pump. Any suggestions on what to try next?

[RF Overlord]

Wow...that's a different problem...

Can you jumper 12V to the solenoid to confirm it opens?

[shou]

I'm working on the car over at my other garage and I didn't have stuff to try that there, but I did bring home one of the new solenoids to mess with. Just put 12V to it and it works just fine. I had also tried one of the old solenoids in the car and it didn't work.

Just thinking out loud here, but I wonder if a relay (if there even is one in it) in the control module went bad. The comp had been growling/dying for awhile. As to how often I'm not sure because my wife was driving it at the time it was failing. Think maybe something got cooked from running often trying to maintain height?

The car also has been sitting with the suspension deflated and the battery disconnected since early July in case that matters.

[RF Overlord]

So the new solenoids work out of the car, but not in it?

There are no relays in the RAS module, which is combined with the VAPS; it's all electronic. I suppose it's possible the module is bad. You'll have to try one from another car to tell for sure. Any CV/GM with RAS will be the same.

Another possibility is damaged wiring.

[FW_Linc/Merc]

Make sure you open and close the drivers door with the key in the ignition. The car needs to think you are inside it and ready to start the car for the complete compressor cycle to operate.

The ride height sensor must send a signal to the solenoid to open it. If the ride height sensor was working before and you did not mess with it then it is very unlikely that the sensor is bad. Sometimes I have had to push/pull the car up/down to start the bag fill. (pushing on the bumpers)

There is also a rubber o-ring seal that goes into the top of the bag where the solenoid mounts. If not installed correct or damaged I have had problems filling the bag. It is also worth mentioning that either rear bag/solenoid can be the source of the problem.

The pump can run for 2-3 minutes without damaging the pump during the initial fill.

[RF Overlord]

Make sure you open and close the drivers door with the key in the ignition. The car needs to think you are inside it and ready to start the car for the complete compressor cycle to operate.

The ride height sensor must send a signal to the solenoid to open it. He said the compressor runs...wouldn't that clear the ride height sensor?

[shou]

I only brought 1 new solenoid home, the one I replaced with the old one. I'll bring my jumping gear with me next time and test them all.

The odd thing to me, and I'm going to double check it, is that the comp wouldn't run with a solenoid unplugged. Does the control module have a way of sensing a fault?

Here is the way it's going. I have the car on a 4 post lift. The chassis is jacked so that the new bags are resting on the axle housing. Cetainly low enough for the AS to want to raise it. Turn the key on and comp starts in a few seconds without opening the drivers door. Comp runs for 5 seconds-ish then stops. Turn off and back on, if I haven't done anything to release air from the lines, comp vents a burst of air, then runs for 5 seconds again. It will not run again unless I turn the key off/on.

For the control module does it just need to be from that generation CV/GM? I'm going to see if I can get a boneyard one for testing.

[FW_Linc/Merc]

Whenever I replace the bags I removed all jacks and leave the car squatting on the ground. Then put the key in the ignition and then open and shut the door with the hood open. I watch the compressor and walk around the car to make sure it is lifting/filling. The ride height sensor is very sensitive and if the car is higher than the inflated bag would put the sensor the system will fill the air in the line but not open the solenoid. A tilt will also affect the filling. Just because the compressor turns on does not mean that the ride height sensor is working as required. My Mark 7 have 3 sensors and I can tweak the height of the car by moving the sensor locations less than an 1/8". I have had Ford cars with air suspensions for 20 years and never had a control module go bad. I have also never had to replace a compressor (I know others have) but I have replaced more bags than I care to count.

[shou]

I've had the chassis resting on the stops at one point.

It looks like the rod for the height sensor comes off. Should I pop it off and move it around a little? I would loosen the bracket, but it's pretty rusted. I'm going to get a replacement for it soon. I'm going to wait on the bracket as it looks like one comes with the new sensor if that's what I need. Won't need 2 of them.

[shou]

So when you start the car does it always vent, then fill the lines?

Turn my key on, pump vents then runs for 5 seconds or so and I get the suspension light lit.

I'm kinda wondering about the height sensor now. It is pretty rusty up in there.

[RF Overlord]

The ride height sensor is very sensitive and if the car is higher than the inflated bag would put the sensor the system will fill the air in the line but not open the solenoid. Just because the compressor turns on does not mean that the ride height sensor is working as required. My Mark 7 have 3 sensors The Marauder only has one sensor. This is where I'm confused. My understanding is that if the car is low,the sensor tells the module that, and the module in turn tells the compressor to turn on and the solenoids to open. It appears that the sensor only tells the module whether the car is high or low...I don't see how the sensor can control the compressor and the solenoids separately.

[shou]

I took a stab at the height sensor as it was very rusted. It didn't solve the problem though. It was real hard to turn it so I figure it's days may of been numbered anyway.

I found that not only does the comp not run when a solenoid is unplugged, you get the AS warning light instantly. Plugged back in the comp does it's 5 second run then the light comes on. This leads me to believe the wiring is ok.

I have a module on the way.

And thank you guys for you input :burnout:

[Comin' in Hot]

I bet its the ride height sensor

[shou]

Well it wasn't the module either. After that didn't work I was feeling pretty defeated.

I swapped out the one solenoid I had tested fine with 12V earlier, but hadn't swapped it with an old one, and it worked!

Weird thing is I got the service manual the other day off eBay and it says the solenoids should meter 10-17 ohms and this one reads 15 ohms. Going to ask Suncore about it when I call to get another new one.

Thank you again for your help guys :burnout:

[RF Overlord]

So you swapped one of the new solenoids for an old one and now everything works fine?

[shou]

Correct.

I had swapped one of them when I was over at that garage and didn't have anything to jump 12V to test them with.

I still kinda wonder what's up with this as the solenoid that makes the system not function, tests as good by actuating with 12V and measures resistance within specs. I'm just glad it works now.

[RF Overlord]

That's weird.

According to the factory wiring diagram, the two solenoids are completely separate circuits from the control module. I don't know how having just one be defective could take down the whole system...unless it was shorted and taking down the internal power feed, but then unplugging it should have restored operation, even if only to one air bag.

[jaywish]

What he said. I can't see that either, I would have expected one bag to inflated with one bad solenoid.

[shou]

I absolutely agree that it's weird. Almost to the point that I wonder if I did something idiotic!

I wonder if the module can somehow sense an issue with one of the sols being that it might be a bad thing to have just 1 solenoid functioning. Not sure how that it could do that though. It's not like the 1 sol worked for a second or two, then the system shut down when the 2nd didn't work.

The system will not work at all with an unplugged solenoid and you get an immediate suspension warning light. I imagine that's known to the module by the resistance of the sol.

Would be nice to have the schematic for the module.

I can't find it now, but I saw a post where someone shared a link to "More than you'll ever want to know about Ford air suspensions." Does anyone have that handy?

[RF Overlord]

That was me and it's here (www.lincolnsonline.com/tech/00061.html).

There are no schematics, though...