P38A EAS jumping around

Wazzajnr · May 25, 2017

OK, first run on the motorway today since new bags and shocks. All works as expected except when in highway mode where it's constantly adjusting. Never did this before.
I thought at first it was the back but watching it when driving I saw it was the fronts jumping to 120+ bits then at few seconds later dropping to 80 bits. Seems to do it on a fairly regular basis, enough to be annoying certainly! The target bit counts seem to be reasonable numbers and not miles apart.
Any ideas what could cause this behaviour?
Cheers in advance.

Grrrrrr · May 25, 2017

Bit of dirt on the track of the height sensor?

Can you get a trace with the Nanocom of a ten minute journey?

Wazzajnr · May 26, 2017

Grrrrrr said:
Bit of dirt on the track of the height sensor?

Can you get a trace with the Nanocom of a ten minute journey?

Going to have a closer look today. I'll try to get a trace but I'm a long way from a motorway at the moment and it only happens on motorway height, never in standard height.
If it was dirt on the sensor, wouldn't that manifest itself in all height ranges?.
Cheers.

Grrrrrr · May 26, 2017

Wazzajnr said:
Going to have a closer look today. I'll try to get a trace but I'm a long way from a motorway at the moment and it only happens on motorway height, never in standard height.
If it was dirt on the sensor, wouldn't that manifest itself in all height ranges?.
Cheers.

My thought was that it might just be the part of the track that it sits on at motorway height. Maybe going between access and high ride height a few times might clear it.

Wazzajnr · May 26, 2017

Grrrrrr said:
My thought was that it might just be the part of the track that it sits on at motorway height. Maybe going between access and high ride height a few times might clear it.

Could be, I'll drive it up and down a few times and I'll capture the data whilst doing it. Hopefully, if there is a bad bit of track it'll show up.
Cheers.

Wazzajnr · May 26, 2017

Is there any way to force it into motorway height?? Can find all the other heights on nanocom but not motorway height.

tomcat59alan · May 26, 2017

Wazzajnr said:
Is there any way to force it into motorway height?? Can find all the other heights on nanocom but not motorway height.

Drive over 50 mph then lock it

Wazzajnr · May 26, 2017

tomcat59alan said:
Drive over 50 mph then lock it

Problem is, it's about 40 minutes to the nearest road where I could achieve 50mph long enough for it to drop.
Seems to me that nanocom should have this feature available.
Doesn't help not having any measuring blocks, I'd love to reset the heights with known blocks and see how it goes then.

tomcat59alan · May 26, 2017

Have you done a search, I think I remember a forum member having a dancing 38 and he/she changed the driver pack, which should not have made any difference but it cured it.

brianp38dse · May 26, 2017

To select motor way press the inhibit button then press the height button down, it works on mine, I drive it on low nearly all the time.

Wazzajnr · May 26, 2017

tomcat59alan said:
Have you done a search, I think I remember a forum member having a dancing 38 and he/she changed the driver pack, which should not have made any difference but it cured it.

Yes, much to the OH's dismay I spent all last night searching but couldn't find anyone with my symptoms.
Most are a case of the front dancing around at traffic lights when equalising and not dropping like a brick on the motorway setting.
I'm just having a look now, I'll post up the settings in a while.

Dippypud · May 26, 2017

Wazzajnr said:
Yes, much to the OH's dismay I spent all last night searching but couldn't find anyone with my symptoms.
Most are a case of the front dancing around at traffic lights when equalising and not dropping like a brick on the motorway setting.
I'm just having a look now, I'll post up the settings in a while.

Can you not borrow a known good one to check ?

Wazzajnr · May 26, 2017

brianp38dse said:
To select motor way press the inhibit button then press the height button down, it works on mine, I drive it on low nearly all the time.

Yep, that works, thanks.

Wazzajnr · May 26, 2017

OK, on measuring the wheel centres to the arch lip, I found that the front was way too high (470mm in highway and over 500mm in standard)
I've reset them to as near as I can measure, the correct heights of 445 motorway and 470 standard and I'll just have to see how it goes next time I get to the motorway.
Once I get home, I'll get some blocks made and measure it correctly and let you all know how it goes then.
Hopefully I've done enough to stop it bouncing around!
Cheers for all the help gents.

wammers · May 26, 2017

Wazzajnr said:
OK, on measuring the wheel centres to the arch lip, I found that the front was way too high (470mm in highway and over 500mm in standard)
I've reset them to as near as I can measure, the correct heights of 445 motorway and 470 standard and I'll just have to see how it goes next time I get to the motorway.
Once I get home, I'll get some blocks made and measure it correctly and let you all know how it goes then.
Hopefully I've done enough to stop it bouncing around!
Cheers for all the help gents.

I think you found your problem.

Wazzajnr · May 26, 2017

wammers said:
I think you found your problem.

I hope so! 900 miles in the next week with it bouncing up and down will result in petrol and match being deployed!
I know I'll have to set it up properly but hopefully this will do for now.
It certainly feels much more stable in standard.
Guy who did it is a disco expert so only used to doing the rears. He's done a good job by and large but he obviously got the front a bit wrong!
Would you be willing to lend me your setting blocks for a few beer tokens? Just saves me getting some made up.
Cheers.

wammers · May 26, 2017

Wazzajnr said:
I hope so! 900 miles in the next week with it bouncing up and down will result in petrol and match being deployed!
I know I'll have to set it up properly but hopefully this will do for now.
It certainly feels much more stable in standard.
Guy who did it is a disco expert so only used to doing the rears. He's done a good job by and large but he obviously got the front a bit wrong!
Would you be willing to lend me your setting blocks for a few beer tokens? Just saves me getting some made up.
Cheers.

There are parameters (high and low) acceptable bit counts for each height. If you set an height too close to the low or high limits the suspension can jump or drop to the next height. It is very important on the front end to get the side to side counts as near to each other as possible within the upper and lower allowable bit count. As the vehicle comes to a halt the front valves open to equalise pressure across the axle, if the side to side bit counts are too far apart this will cause the front to appear to dance up and down. Rear is not affected.

Wazzajnr · May 26, 2017

wammers said:
There are parameters (high and low) acceptable bit counts for each height. If you set an height too close to the low or high limits the suspension can jump or drop to the next height. It is very important on the front end to get the side to side counts as near to each other as possible within the upper and lower allowable bit count. As the vehicle comes to a halt the front valves open to equalise pressure across the axle, if the side to side bit counts are too far apart this will cause the front to appear to dance up and down. Rear is not affected.

Many thanks as ever!

PPP38vouge · May 26, 2017

Hi, I too had the same problem that you are having a few years ago after changing the air bags. When I first purchased the car the suspension was working as it should with no problems, as I was new to P38 ownership at the time I joined this wonderful forum and done tons of reaserch on what to look out for and decided soon after to check the bags, although they were not leaking they were very perished and I believe we're the original bags, so, armed with tools in hand changed out all four bags, things seemed OK for a day or two then I noticed the front was dropping and rising as I was driving a long and when I was stationary at traffic lights the front was dancing all over the place, as mine is the later RR I read that it's possible to swap the front height sensors over which I did but unfortunately did not solve my problem. As Grrrrr mentioned earlier regarding a dirty track on a height sensor that's what had happened to mine, on changing the bags I may have let the front axle hang to low thus moving a height sensor out of normal range, in the end I replaced both front sensors, recalibrated and she has been as good as gold now for the past 4 years.
Hope this helps.
Paul.

Wazzajnr · May 26, 2017

PPP38vouge said:
Hi, I too had the same problem that you are having a few years ago after changing the air bags. When I first purchased the car the suspension was working as it should with no problems, as I was new to P38 ownership at the time I joined this wonderful forum and done tons of reaserch on what to look out for and decided soon after to check the bags, although they were not leaking they were very perished and I believe we're the original bags, so, armed with tools in hand changed out all four bags, things seemed OK for a day or two then I noticed the front was dropping and rising as I was driving a long and when I was stationary at traffic lights the front was dancing all over the place, as mine is the later RR I read that it's possible to swap the front height sensors over which I did but unfortunately did not solve my problem. As Grrrrr mentioned earlier regarding a dirty track on a height sensor that's what had happened to mine, on changing the bags I may have let the front axle hang to low thus moving a height sensor out of normal range, in the end I replaced both front sensors, recalibrated and she has been as good as gold now for the past 4 years.
Hope this helps.
Paul.

Thanks for that. I think I might treat it to new sensors when I get home anyway, the objective of this post was to make it bearable for the next week driving back through Germany.
I think what I found today should have fixed the immediate issue and it will get treated when I get back.
Still have the refurb kit for the valve block as well so need to get that done.

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