If I disconnect the low pressure switch (three prong)on the line at the compressor the fans will quit.
That 3 wire harness is going to your pressure sensor...if you disconnect it, you are shutting down the system....
I am guessing I am getting the signal from the dash control since the fans turn on.
That sounds right....
I do not have a pressure switch on the accumulator.
there is none, because you have a pressure sensor in the line to the compressor......if that sensor is bad, giving too high a reading or too low a reading, the PCM will disable the compressor.....Have you checked for PCM codes?
No voltage at the relay on the firewall. I can apply 12 volts to the plugs green wire going to the compressor and the compressor kicks in. Has cold air. If there is a cycling switch to bypass I do not know where it is.
There is no pressure cycling switch in this system, like there use to be on the old systems(the pressure cycling switch use to be on the accumulator).....and you can't bypass the pressure switch....BUT......you should have voltage on two legs of the compressor relay sockets(pink wires)....did you check this with the key in the run position? If yes, then there is a blown fuse or open wire.....When the PCM receives a request from the control head, which it seems to be doing with the fans running, it then grounds the clutch relay......it won't if there is a pressure switch problem, or if there is a code set.....could also be a bad wire between the relay and the PCM....or even a bad relay, if you do have power to the relay....