I have an L322 2006 range rove and recently refurbished the air drier and pump (Hitachi). The compressor is working but it shuts off after a few second of operation. The fault code say the compressor pressure sensor and the reservoir is filling up too slow. I hears a hissing sound coming from the canisters on the side of the compressor pump and drier. I think these are the reservoir. Could this be caused by the fact I did not replace the relay? I've been told that no reprogramming is necessary. Can some one help me with this? What I'm I missing?