Hi,

This error will come up when the compressor switched from 'unload' to 'load' and there's no increase in pressure sensed.

The compressor then assumes that the loading valve (inlet valve) is malfunctioning.
The inlet valve is a big valve on top of the compressor screw element that regulates the intake of air to the air compressor. When it's closed, no air is drawn in and the compressor runs 'unloaded'.

When it's open, air is drawn in, the compressor pumps air and the compressor runs 'loaded'.

So when the compressor opens the inlet valve, and there's no increase in pressure... it assumes the loading valve (inlet valve) is still closed / malfunctioning.

Please check the loading valve. Does it open and close? You can usually hear a distinct difference in noise when a compressor switches from 'unload' to 'load'.

If that's not happening, let me know and we'll investigate further.

All the best,
Cas

No loading in my ROC L6 compressor