BMW E70 Rear axel Air suspension

[Greydog]

About 3 weeks ago I started to get an air suspension issue, the compressor would over run and timeout. There are no leaks as I pulled the compressor fuse to protect it and the car will sit for a week or more without dropping.
So finally got some time to check over the system, I started with a visual check of wiring to the rear sensors and tested continuity between the EHC connector and sensor plugs (had an issue there before) I found nothing this time. So replaced the fuse and plugged in the diagnostics, the compressor ran and raised the suspension far to high on the left, right didn't move the compressor ran until it timed out. Diagnostics showed 4 codes 5F94 Solenoid valve Left 5F95 Solenoid valve Right 5F96 EHC Drain valve 5F99 Control time fault rear right.
Talked to an old friend who works for BMW who asked their technical department sadly they couldn't offer any help as their solution is replace the compressor complete with solenoid block and sensors (and BMW prices that's nuts)
The compressor is easy to remove from the car so off it came and I serviced it, checked the dryer wasn't wet, took off the drain valve cleaned it and tested the solenoid vale was functioning did the same with the solenoid block all OK so back together and on the car
Compressor runs and lifts the car to above standard height and again over runs and times out !!! Now I only have one code 5F99 Control Time Fault rear right
So I have changed the rear right ride height sensor (New correct part number) and run live Data Left rear sensor shows 5.02v and ride height +20mm Right rear sensor shows 5.04v but -127mm ?? Yet when measured at the wheel rim to wheel arch ride height is 750mm (should be 720 to 730) I can manipulate ride height (lower/raise) through ISTA my problem is I can't clear the right rear sensor which constantly reads -127mm that I believe is the reason for the overrunning compressor which if left will burn out?? Sorry for War and Peace
Any body got any ideas or experience of similar all help gratefully received it's hurting my old brain now

[X5Sport]

Shooting in the blind as not come across this…..

Is there a calibration procedure to ‘teach’ the car/system about the new sensor?

Was the new sensor OEM or a copy part? Might be a faulty sensor?

[Leslie]

Broken sensor wire somewhere along follow it back id say as a guess

[Greydog]

Hi guys
Thanks for the input
Leslie. I have checked visually then carried out a continuity test on both the left and right sensor wiring between the EHC Connector and the sensor plugs, they both check out OK so not a broken wire. Also checked power both are receiving the correct 5v just checked again to be sure.

X5Sport. I have both INPA and ISTA and yes there is an Adjustment/Calibration routine which should be followed after any changes to the suspension, as the right hand sensor has been changed I did run the procedure. The new sensor is Hella (OEM supplier) and supplied to the correct part number so should be OK. However tomorrow I will swap left for right if the issue moves it should confirm whether the sensor is OK or not I will also carry a test on the old sensor.

Thanks Chaps I will carryout more research stir the old grey matter it is a simple system why is it being so obstinate Time for some headache pills or may be a beer will help

[Leslie]

Can the little link rod flip backwards on these giving odd readings ? Id disconnect the little rod and move it up and down and see what the feedback shows and if its moving as the arm moves .

is the left reading +750 and the right -127 ,is that correct , does the right stay the same even when unplugged ? I wonder if that is some default valve as it im guessing should not be minus ? sounds like it isn't getting any actual feedback .
The left to right swap is the next step like you say