From another thread I have gleaned that the compressor is rated for a 15% duty cycle which equates to 9 mins total running time per hour.
I am told that the pump only runs when ‘on the move’ the pressure switch detects a drop in pressure i.e. when there is a change of height requested or when there is a leak on the reservoir’s side of things. Now I know this can’t be the case because when previously I had a minor but definite leak on the air tube to the NSF air bag the system would try and keep that air bag inflated whilst travelling 100’s of miles on motorways without the speed dropping significantly. The only way it could do this was if the height sensor told the system that that corner was drooping slightly.
Now when my compressor was incorrectly mounted (my fault) it was very obvious when it ran due to the vibrations and noise. The obvious vibrations were only very noticeable during last few seconds of ‘top up’ when back pressure was high. I noticed that the compressor would run for a few seconds only and mostly (but not always) when I applied the brakes. I now believe this was due to the front suspension compressing, the height sensor providing the reduced height reading and the system operating to counteract the movement. Hard cornering would have the same effect. Once rebounded the system would be too high and air allowed out to bring the suspension back within limits. This continual operation would result in the reservoir pressure inexorably dropping over time and the compressor running to replenish the reservoir tank.
It was also noticeable that on a motorway/A road drive the compressor would seldom run giving further credence to this continual compensation when on the move. Does anyone know definitely how the system works on the move and if my assumption is wide of the mark?
Furthermore, there are no leaks when the vehicle is parked up for days as the ride height is rock steady with no sagging and when moving off the suspension goes quickly up to normal height. I do not have a pressure gauge fitted so cannot swear to absolutely no leak on the reservoir side but I would think after a week stood standing with even a small leak it might struggle a little bit to get up to normal ride height.
Does anyone know how long an in spec compressor should take/run (mine is in rude health) between the two operating limits of the pressure switch? From my rough estimation the compressor would run in town driving (frequent braking) for a total time of much less that 9 mins an hour. Now I have corrected the compressor mounting I can’t really detect when it’s running when on the move so can’t measure its overall running time.
However, having said all that I have the feeling that the on/off limits on my pressure switch may be a bit too close together resulting in the compressor switching on too often (albeit for short durations) and without fitting a pressure gauge the only other way to do a rough test is by timing it’s running period.