P38A Cycling EAS

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Hello, please can I ask for further help with my P38 cycling EAS, or dancing front end?

I've had massive improvements to the EAS since fitting Kurt's rebuilt valve block but some problems remain - mainly the cycling between the the compressor pumping the front end up, and then valves letting it down again. A complete cycle is perhaps 10 to 20 seconds and the cycling can last for any amount of time - but it can also stop!

I've plugged a Nanocom in and the live height readings do not fluctuate wildly, but by perhaps one digit ( 101 to 102 for example). During the cycling I can see the front end readings rise over perhaps 10 seconds, then the compressor switches off, the valve block clicks, the front falls over a couple of seconds, then the cycle starts again.

Because there is no wild fluctuations in the live height readings does this suggest that the height sensors (and connections) are sound?
The live readings show both the Lower Switch and Raise Switch remaining ON all the time. Is this correct?
The Park/Handbrake switch also remains ON, whether the handbrake is on or not.
The Valve Status on all valves are always CLOSED (although I may have seen one change to OPEN just once).

Any of the above suggest any problems to anyone?

I've never used a Nanocom (or any other fault code reader) before so this is a voyage of discovery for me, all suggestions welcome.

Happy New Year everyone, Cheers, Bertie
 
By the way, I would have checked the height sensor connections as several have suggested but whenever I have the time it's raining, or snowing! I'll certainly have a look when tome and weather allow.
Cheers.
 
Hi RangeRoller, thanks for your reply.

Set heights are:
Front (l and r) 101 and 106
Rear (l and r) 110 and 102

When everything is stable actual heights match, or are one digit out. When the front is cycling actual height increase to perhaps four or five digits above set height, then fall to a digit or two below. Left and Right do not rise by exactly the same amounts.

Handbrake light goes off when it's released but the live readings on the Nanocom show ON for Park/handbrake, whether on or released.

Cheers.
 
Bertie Wooster said:
Hello, please can I ask for further help with my P38 cycling EAS, or dancing front end?

I've had massive improvements to the EAS since fitting Kurt's rebuilt valve block but some problems remain - mainly the cycling between the the compressor pumping the front end up, and then valves letting it down again. A complete cycle is perhaps 10 to 20 seconds and the cycling can last for any amount of time - but it can also stop!

I've plugged a Nanocom in and the live height readings do not fluctuate wildly, but by perhaps one digit ( 101 to 102 for example). During the cycling I can see the front end readings rise over perhaps 10 seconds, then the compressor switches off, the valve block clicks, the front falls over a couple of seconds, then the cycle starts again.

Because there is no wild fluctuations in the live height readings does this suggest that the height sensors (and connections) are sound?
The live readings show both the Lower Switch and Raise Switch remaining ON all the time. Is this correct?
The Park/Handbrake switch also remains ON, whether the handbrake is on or not.
The Valve Status on all valves are always CLOSED (although I may have seen one change to OPEN just once).

Any of the above suggest any problems to anyone?

I've never used a Nanocom (or any other fault code reader) before so this is a voyage of discovery for me, all suggestions welcome.

Happy New Year everyone, Cheers, Bertie
Click to expand...

Can you stick an SD card in the Nanocom and record a trace of the EAS for maybe 10 minutes? Transfer the csv file to your PC, zip it and then post it here.

If all 4 valves are showing closed and the front is rising then I can only think it is the solenoid leaking in the valve block or it thinks they are closed but a dodgy connection to the driver pack is opening it somehow. @pwood999 has played extensively around this area.
 
Sounds like exactly what I had.
A dodgy sensor. To rule it out, take the sensor off the vehicle that's twitching. (they should be solid). Put it on the bench and check with a dvm. Sweeping the arm from extent to another and very slowly, watch for any jumping in the figures. I found with one of mine that at normal road height position (arm at 90° to the two bolt holes on the sensor) it would flicker the dvm readings. There should be no flickering at all but an nrv leaking will also cause this.
Open a door or boot lid with the car running and see if it continues, in theory a leaking nrv will still leak and the car will lift, a sensor problem will not move the car due to the system being disabled . ;)
Edited to be a bit clearer, sorry Bertie.
 
Last edited:
Grrrrrr and Mark. Two helpful suggestions, many thanks. I'll start with the recording if I can find a record button on the Nanocom, and will look at the sensors when the snow melts and before the east winds arrive - I don't have anywhere under cover to work at the moment.
 
Couple of points to add:
  • Front Left-Right target values should be within +/- 2bits of each other. Otherwise the ECU will try to adjust to targets, and after that op both front valves to equalise the front air bags. If the targets are too far out it causes cycling.
    • To fix it put the car on blocks, and carefully bend the sensor brackets to get the bit values equal.
  • Recording a Nanocom trace is better than using screen values for live data. Not 100% sure but the screen update seems to be slower than what's recorded onto the SD Card.
  • Double check all the inputs such as Handbrake, Doors, etc.(and fix them). These change the ECU operation, so behaviour when parked may not match when driving !!
  • Intermittent Driver to Solenoid connections will probably have more impact while driving due to vibration. When parked, they either work or don't.
  • Make sure the tank is full before doing any live traces.
Even with a perfect valve block, I have seen some internal leakage between the tank and corners. This does depend on relative pressures in each, plus the rubber hardness, dimples on the faces & strength of the small spring inside.

My system was refurbished completely 2 months ago, but I still have random "rising while parked" syndrome. I suspect it depends how full the tank is when I stop the car. Some mornings the rear has risen, but once or twice a week the rear has dropped ?? When it's risen, the system levels within a few seconds of starting & pump acts normally, but if the rear has dropped it seems the tank needs filling as well. I also suspect it depends how well the valves seat into the dimples on the plunger faces. My system has self-levelling disabled when ignition is off, so avoids that complication.
 
I would follow Mark and have the system running when you open the tailgate or a door. System should stop instantly. If still cycling then I would suspect an electronic problem.
If system randomly shoots to wade height then I would suspect the driver pack. No idea why.
 
pwood999 said:
Couple of points to add:
  • Front Left-Right target values should be within +/- 2bits of each other. Otherwise the ECU will try to adjust to targets, and after that op both front valves to equalise the front air bags. If the targets are too far out it causes cycling.
    • To fix it put the car on blocks, and carefully bend the sensor brackets to get the bit values equal.
Click to expand...

Just on the first point, you can divide the difference between left and right sensor and just use the average value as the target height. It won't make that much difference to the height.
 
Bertie Wooster said:
I'll start with the recording if I can find a record button on the Nanocom,
Click to expand...

Looks like one of the old floppy disks. Only works with SD card inserted. Sometimes it won't record unless it is a specific format type. Might be FAT32 but it will be in the instructions somewhere. I've got a suspicion it doesn't like extended FAT.
 
Good morning, and once again, many thanks for all your suggestions. It's snowing and -4 deg C here so I haven't done all the suggested tests yet but these are the results of some:

1) The cycling stops when a door is open.

2) I reset the height settings from Front Left 101 and Right 106, and Rear Left 110 and Right 102 to an average of the left and right - 103 both front and 106 both rear. The cycling continued and the actual heights shown on the Nanocom became:
Front left 98 - 101 (target 103)
Front right 106 - 109 (target 103)
Rear left 106 - 107 (target 106)
Rear right 107 - 108 (target 106)

So, the actual heights shown on the Nanocom for the front two wheels were 2 to 4 digits below target on the left and 3 to 6 digits above target on the right. These actuals were in fact little changed from readings given before the set heights were changed. They didn't change to follow the new settings.
The rear actual reading however changed to match the new settings. Could this suggest duff front sensors? I'll have to remove them to check resistance as soon as the weather warms a bit.

3) The handbrake light on the dashboard goes on and off as the handbrake is raised and dlowered.. But the live reading on the Nanocom says handbrake ON at all times. Any suggestions on how this could be checked.

4) Finally, when I first started the car this morning, the suspension had dropped a little overnight and would not rise - doors open or closed. Normally it rises almost immediately. After five minutes I pressed the "Raise" switch and it immediately rose to standard height. Could this suggest an electrical fault?

Phew, time for a coffee now.

Cheers, Bertie
 
If a door is open the system will pause after a while and the button pressed to un-pause the system. It'll drop over night as the becm tries to level the car. The suspension shouldn't adjust with any door or boot open. If it does its usually a mechanical leak.
 
Bertie Wooster said:
Good morning, and once again, many thanks for all your suggestions. It's snowing and -4 deg C here so I haven't done all the suggested tests yet but these are the results of some:

1) The cycling stops when a door is open.

2) I reset the height settings from Front Left 101 and Right 106, and Rear Left 110 and Right 102 to an average of the left and right - 103 both front and 106 both rear. The cycling continued and the actual heights shown on the Nanocom became:
Front left 98 - 101 (target 103)
Front right 106 - 109 (target 103)
Rear left 106 - 107 (target 106)
Rear right 107 - 108 (target 106)

So, the actual heights shown on the Nanocom for the front two wheels were 2 to 4 digits below target on the left and 3 to 6 digits above target on the right. These actuals were in fact little changed from readings given before the set heights were changed. They didn't change to follow the new settings.
The rear actual reading however changed to match the new settings. Could this suggest duff front sensors? I'll have to remove them to check resistance as soon as the weather warms a bit.

3) The handbrake light on the dashboard goes on and off as the handbrake is raised and dlowered.. But the live reading on the Nanocom says handbrake ON at all times. Any suggestions on how this could be checked.

4) Finally, when I first started the car this morning, the suspension had dropped a little overnight and would not rise - doors open or closed. Normally it rises almost immediately. After five minutes I pressed the "Raise" switch and it immediately rose to standard height. Could this suggest an electrical fault?

Phew, time for a coffee now.

Cheers, Bertie
Click to expand...

If it doesn't raise straight up in the morning but does after a few minutes then I would suspect leak in supply side, possibly the line to the tank. Possibly the air-dryer.
 
Bertie Wooster said:
Good morning, and once again, many thanks for all your suggestions. It's snowing and -4 deg C here so I haven't done all the suggested tests yet but these are the results of some:

1) The cycling stops when a door is open.

2) I reset the height settings from Front Left 101 and Right 106, and Rear Left 110 and Right 102 to an average of the left and right - 103 both front and 106 both rear. The cycling continued and the actual heights shown on the Nanocom became:
Front left 98 - 101 (target 103)
Front right 106 - 109 (target 103)
Rear left 106 - 107 (target 106)
Rear right 107 - 108 (target 106)

So, the actual heights shown on the Nanocom for the front two wheels were 2 to 4 digits below target on the left and 3 to 6 digits above target on the right. These actuals were in fact little changed from readings given before the set heights were changed. They didn't change to follow the new settings.
The rear actual reading however changed to match the new settings. Could this suggest duff front sensors? I'll have to remove them to check resistance as soon as the weather warms a bit.

3) The handbrake light on the dashboard goes on and off as the handbrake is raised and dlowered.. But the live reading on the Nanocom says handbrake ON at all times. Any suggestions on how this could be checked.

4) Finally, when I first started the car this morning, the suspension had dropped a little overnight and would not rise - doors open or closed. Normally it rises almost immediately. After five minutes I pressed the "Raise" switch and it immediately rose to standard height. Could this suggest an electrical fault?

Phew, time for a coffee now.

Cheers, Bertie
Click to expand...
Also if one corner raises it'll affect the opposing side and will influence the rears somewhat.
Watch the live data. Watch each corner and if you see one that goes up and down even one or two digits it may be the suspect.
Then when its suitable remove it and check. A good sensor has no need to read anything other than a solid reading unless the car is tilted by yourself.
 
I don't think the delay in raising this morning was a leak. It had been running with doors open for a while then nothing happened when I shut the doors. As soon as I pressed the 'raise' rocker switch it shot up. Mark's suggestion about the system being in 'pause' mode and needing a switch pressed to un-pause it makes sense.

I don't really think I'm going to know much more until I look at these height sensors. Next job ...... In the mean time I've ordered a card for the Nanocom to record live readings.
 
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