Diagnosing air suspension problem

[Tote]

Is anyone familiar enough wit the air suspension system to assist with diagnosis of the following problem?
In the mornings the suspension light comes on immediately if a height change is attempted. If left alone the compressor will run for a couple of minutes and when you move off a fault will usually be logged. This has been occurring since before we left on our trip but prior to leaving no faults were permanently logged. I suspect I have a slow leak that is emptying the tank but don't know where to start looking. Do the lines to the compressor stay at tank pressure or is there another valve? Once the vehicle is running everything goes normally Any suggestions welcome
Regards
Tote

[CaverD3]

Check the dryer to see if the desicant is damp and has expnaded?

[Neil P]

+1 on that .

If you've got a fault code reader , check pump vacuum fault.

[Graeme]

Do the lines to the compressor stay at tank pressure or is there another valve?
The pressure in the lines from the compressor to the reservoir valve and the front and rear valve blocks is always dumped as soon as the compressor is stopped, excepting if the exhaust valve is siezed shut!

The compressor should not run for so long. Most likely the vehicle is too slow to raise which causes a fault to be logged.

As well as a possible clogged dryer, the compressor outlet valve could be worn-out, so hopefully its either this or the dryer rather than the compressor itself. With the dryer removed from the compressor, you should be able to blow through the dryer albeit with some resistance. The dessicant can be removed from the dryer and dried in a micro-wave oven. New dryers are available, as well as outlet valves for at least some versions of the compressor.

[Graeme]

check pump vacuum fault.Pressure?

[CaverD3]

Yup drier is easy to fix. remove compressor and remove drier. Then empty contents into abowl and microwave till dry. Reasemble and it should work.
Just did mine. Now goes up quick and farts properly.:D

[Tote]

Ok, an update. I fitted a spare compressor that I had put a new exhaust valve in with no real difference in the fault displayed. A couple of observations:
The compressor I pulled out is the current part number and less that 12 months old
The spare compressor is an older one but is noticably quieter running.

I am still experiencing the same symptoms where I will get a couple of suspension faults in the morning and then the vehicle will work fine all day. The number of faults is intermittant and occasionally will occur in the afternoon if parked all day and sometimes I wont get a fault at all that day.

Vehicle is not dropping overnight

When I replaced the compressor after the vehicle had been sitting for a while the hose that connects to the blue connector on the drier was slightly pressurised. I would have thought the pressure would have been vented from this line when the compressor shut down.

BBYER, can you please repost those links on the schematics from the UK forum as I couldnt find them with a search before you posted them.

Regards,
Tote

[Graeme]

The noisier compressor is probably the better one but suggests a blocked dryer. Have you removed its dryer and tried to blow through it?

[Tote]

Yep, both driers are easy to blow through with only a small amount of resistance.
Regards,
Tote

[Graeme]

It sounds like it may be time to find out what the codes are indicating in case there's something a bit unusual. Mine got to be slow to rise some time after a new compressor was fitted and it wasn't until I spotted then fixed a reservoir valve error that proper operation was restored.

[Tote]

Some more info...
The old compressor that I put back in has now introduced some new symptoms. I am generally getting a suspension fault (normal height only and the orange dash light ) sometime after starting and am unable to raise or lower the suspension after restarting. This would indicate that the compressor is unable to deliver enough pressure to operate the system under any circumstances which is different to the previous symptoms. I'll put the later model compressor back in with the new valve swapped over and report back.
Graeme, It's due for a service so I'll get the codes checked then but with the previous compressor it wasnt logging any permanent codes after restarting. It's an interesting learning experience playing with this stuff.

Regards,
Tote

[Tote]

As an exercise I disconnected the battery overnight and reconnected it. The compressor fired up immediately and the suspension operated normally. The truck is parked at the airport for a week so it will be interesting to see what it's mood is when I pick it up. Haven't had a suspension fault since I reconnected the battery on Sunday Morning. Maybe I scared it by booking it into the stealer to have the compressor looked at next Monday. (or maybe reseating the hoses from the compressor cured a slow leak and disconnectinmg the battery cleared the errors allowing normal operation)
More drama to come I'm sure......
Regards,
Tote