e30 A/C Relay question - no power to low pressure switch

Another work session, and now my A/C is working as it should. 35 degree air at highway speeds, and the a/c compressor cycling as it should.

I confirmed that with the high pressure switch connected (as an open), the clutch would not engage with the evap temp controller in place or with it removed and a jumper placed between pins 4 and 5. So, at least I had consistency.

I went back to the assumption that the high pressure switch is supposed to be closed in normal operation and disconnected its wires, putting a jumper in place again. I then put the evap temp controller back in place, and tried it. The evap temp controller clicked in, and the compressor clutch engaged. I had 12v at the high pressure switch, low pressure switch, and clutch.

So, what I'm left with from this excercise is that after I replaced the plugged expansion valve and recharged the system, the relay in the evap temp sensor was stuck after years of not being used, or the connectors were corroded. After I took everything apart and moved the relay contacts by hand, and with all the plugging and unplugging, things finally were cleaned up and making contact.

One thing that is important for someone troubleshooting this; because of feedback and some parts of this circuit getting enabled by a ground, if you disconnect the low pressure switch to see if 12v is present, I think the evap control relay will disconnect and the voltage will be removed. I was doing this at first. Check for voltage with the connections in place, and scrape with your probe to make sure you are getting through any corrosion. On this car, it is not a simple +12v -->

Switch --> low psi switch --> compressor clutch circuit. One post I read said to test the evap temp sensor by applying 12v to one of it's leads; in this circuit that would short directly to ground if the sensor was working.

Thanks to all who helped. I hope someone else can use this as well. Let mw know if you want any working diagnostic info.