Ok. Here we go. I have a 2000 Nissan Altima that has 295k on the odometer but just put a new Japanese JDM motor with 30k on it. When I replaced the motor, the a/c worked fine. I did not remove or evacuate the system during the motor swap. Motor is in, running like a top and the A/C will not turn on. I've checked all fuses and relays, had the system evacuated, vacuumed and recharged, replaced the A/c amplifier all to no avail. If I by-pass the relay, the compressor comes on but only Luke warm to slightly cool air comes out. I'm down to the A/C control head, pressure switch or the ECCS. The ECCS is 1 year old .
Any ideas?

Post up what your high and low side pressures are and ambient temperature. That will help determine if at least the AC system is functioning properly and something else is causing the air to be luke-warm.