Hi all - I have the standard yellow suspension warning, 'Normal Ride Height Only' with fault code C1A20. Not the first time and previously used a repair kit for the original Hitachi compressor which improved things but still gave the same fault in off road height.

Ive repaired the compressor again (including end cap, filter beads, filters, o-rings, piston ring etc etc), although the motor gets VERY hot very quickly and slows down as the pressure increases - never had an overheating error though. I am trying to trace the fault to either a leak somewhere in the system or simply a broken compressor.

Firstly, when I log the compressor's activity using a diagnostic machine the compressor reaches pressures up to 200 psi within a few minutes - suggests the compressor is working well. But what should the operating pressure be? When in normal height Ive had it at either 14 psi or 45 psi. How long should the compressor run for?

Secondly, to try and trace an air leak in the system does anybody have an air line diagram? Including the non-return valves etc?

Thirdly, the 'gallery' I assume is the manifold block that controls each corner which is located at the front - but where exactly?

Thanks for the help.

There isn't much in the workshop manual about pressure but there is this;

"The valve block also contains a pressure sensor which can be used to measure the system air pressure in the air springs and the
reservoir. The pressure sensor is connected via a harness connector to the air suspension control module. The control module
provides a 5V reference voltage to the pressure sensor and monitors the return signal voltage from the sensor.
Using this sensor, the control module controls the air supply unit operation and therefore limits the nominal system operating
pressure to 244 lbf/in2 (16.8 bar gage)."

EDIT: there is also this:

Exhaust Valve
The exhaust valve has three functions. It operates in conjunction with the pilot exhaust valve to allow air to be exhausted from the
air springs and/or the reservoir as described previously.
The valve also protects the system from over-pressure. The valve is connected into the main pressure gallery which is always subject
to the system pressure available in either the air springs or the reservoir. The valve is controlled by a spring which restricts the
maximum operating pressure to between 319 to 391 lbf/in2 (22.0 to 27 bar gage).
The minimum pressure in the system is also controlled by the exhaust valve to ensure that, even when deflated, the air springs
contain a positive pressure of approximately 14.5 lbf/in2 (1 bar gage) with respect to atmosphere. This protects the air spring by
ensuring it can still 'roll' over the piston without creasing.

(Note the 'air supply unit' is what Land Rover call whole unit including the compressor in this document)

There is a diagram of the 'air harness':

Click image to enlarge

Thanks Paddi - thats a great help.

The diagnostic code doesnt have '64' at the end but has the 'Pressure increase too slow when filling reservoir' description.

I spent some brief time today looking at the diagnostic machine read out and concur with the workshop manual. 14.5 psi residual pressure, 246 psi 'operating' pressure, and the pressure sensor reference voltage. Although the operating pressure was at 246 psi, the sensor voltage increased slowly from 3.2v to 3.6v over the first minute or so the compressor was active. The compressor then slows to a stop, then the amber light appears and compressor is stopped.

I believe the reservoir valve is open, but needs to be confirmed. Any other thoughts? Is the pressure sensor operating correctly? Or should this be at 5v when at 246 psi?

Thanks again.

JS3 wrote:

Hi all - I have the standard yellow suspension warning, 'Normal Ride Height Only' with fault code C1A20. Not the first time and previously used a repair kit for the original Hitachi compressor which improved things but still gave the same fault in off road height.

Ive repaired the compressor again (including end cap, filter beads, filters, o-rings, piston ring etc etc), although the motor gets VERY hot very quickly and slows down as the pressure increases - never had an overheating error though. I am trying to trace the fault to either a leak somewhere in the system or simply a broken compressor

Thanks Mikey. Even though I repaired the compressor?

The compressor seems to be running longer than it should and the temperature reaches 180 degF within a minute. How long should the compressor run for? And if the pressure is at 246 psi, why does the compressor continue to run?

If the compressor gets hot in a short space of time, its generally a faulty compressor.
An air leak would decrease load on the compressor, and take longer to heat up, but would run longer to generate pressure

By my calculations, working pressure is 1780kPa, or 17.8bar, or 261(ish)psi

Thanks Mikey - when I say heating up, it is the motor unit of the compressor that gets very hot.

Would you investigate the pressure sensor any further? I have around 3.6v at 264 psi. I just want to make sure I fully investigate all avenues before I spend £350 on a new compressor.

Again, thanks for the help.

Thanks for the help guys. I have done some investigating into this fault and could not definitively identify a fault within the air system (thanks to Paddi's list) so opted for a new compressor (last item on the list).

New compressor fitted and no more fault codes. However, the compressor still runs for what seems a long period, around 90 seconds to 2 mins. The struts are inflated within a few seconds when changing height, but the remaining time seems to be spent pressuring the reservoir. There appear to be no major leaks on the reservoir.

Is this time normal? I thought I had read somewhere it should only take 20-30 seconds but could be mistaken.

My son had issues with the pump on his L322 (full fat RR). Its different to the RRS, under the spare wheel in the boot, but the systems are generally pretty similar.

He bought a repair kit, replaced seals, piston etc and it improved a bit but still took ages to lift the car.

In the end he bought a new pump and it has been fine ever since.