I've decided to continue with the project just to see if it's feasible. It's more of a proof of concept than a real solution at this point. My current thinking is to use two vacuum pumps, one dedicated to servicing the brake booster and the other for climate, shutoff and locks. I'm going to attempt to use an Arduino micro-controller to control and monitor the pumps and vacuum. (I say "attempt" because I've no experience with electronics or device programming so this will be a fun learning exercise)
I've done the research and determined that a GM 1 bar MAP sensor provides a linear reading between zero and full vacuum. It's a 5 volt device so it's perfect as an analog vacuum input for the Arduino.
My working plan is to use a potentiometer to allow adjustment of the set point for vacuum. I've got two choices - either two potentiometers to provide a low set value (turn on) and a high set value (turn off) or alternately two potentiometers, one to set the turn on point and the second to control the amount of hysteresis. (Or I may go dirt simple and hard code the on and off points in software and forget the pots)
I'll include code that will monitor the run time of the pump and if it runs continuously for some pre-determined amount of time (10 minutes??) it will turn off and turn on a LED in the dash. I'll also have an LED to show that the pump is running (... more likely one RGB LED that will glow green for pump running, blue for pump running over 5 minutes and red for pump emergency shutdown).
I've got enough control pins available to duplicate the circuit (and code) for the second pump.
I think I can control the pumps with MOSFETs and avoid the need to have external mechanical relays, but that's under investigation. (Even thought about the possibility of using PWM to slow down the motor as it neared the upper set point)
I had hoped to take advantage of the 1/2 price sale at the junk yard to pick up the second vacuum pump for $10 but couldn't find any, so for now I'll try running with one. My biggest concern is getting another leak in one of the vacuum pods, but if I know the pump is exceeding it's duty cycle I can turn off the climate and be OK until I get it fixed.
I'll continue to update as the project continues.... or not.
