My guess would be that either one of the switches or the wiring is having some type of issue.
It's not a complicated system, if it's working correctly then:
The manual I linked earlier has a troubleshooting section that, while it isn't specific for the HMMWV, it does cover the basics. Go to chapter 10 in the guide and read up about the AC clutch circuit.
The flashing lights on the evaporator are just a guide as to where to look, it doesn't tell you the specifics.
https://www.btrac.com/documents/rd-service-manual.pdf
Not to be harsh or anything, but we aren't there in front of the unit and can't point out what's wrong from just a blinking light, so you're going to have to read up and try to understand exactly how the system works in order to figure out what sensor/switches and wiring to check. You'll need a multimeter for all of this (voltage checks at switches and wires, and continuity tests through the same switches, as well as making sure nothing is shorting to ground)
But to say again, the blinky lights first said it was the clutch, and now are saying sensor. To me this means that it's very likely you have either a wiring issue (either a bad connection, shorted connection, or open) or a sensor/switch is not operating within specs.