Jelag, does the condition you describe, low vacuum, allow the brake to close when the reset button is pushed? Or will low vacuum make it close only partially?
My Pacbrake just started to not work a month or so ago, guessing it is the relay, ECM pigtail connection? I think this because my wipers went out at the same time the brake started not working. The Pacbrake had the switch power tied into the orange wire with black tracing under the steering wheel, per the installation instructions.
I have switched the source of power (to the brake), lubed up the brake with the Pacbrake lube, when the reset button is pressed the brake closes and gives the familiar sound and the brake does fully close. I also suspect the ECM pigtail may need to replaced as you have suggested in a previous thread.
I am thinking I will replace the relays tonight and check for proper vacuum levels tomorrow. I will also take off the solenoid and clean it out as well. Any advice? I have read a lot of the other related threads and thought I would put my 2 cents in.