Underwood rotary air compressor

[Walker]

My throttle control arrived today. I purchased an InPower DBT-LD-02 electronic throttle speed control. I went through their website and it really wanted me to buy the $400 speed controller. The one I purchased was $95. The application list on the one I bought was fairly ambiguous about what it worked on, but did say light duty (you dont get to medium duty until you have a 4500/450) trucks and SUVs.

When it got here it had a sheet in it that said 2014+, so I just tried it. It plugs right into the OBDII connector, and there are two extra obdII connectors on its harness if you need to plug it other stuff. It then has 4 blunt cut wires coming off the harness. One is to switch to 12v+ to activate RPM #1 (user adjustable for both rpms), another to switch on RPM 2, a wire used to adjust the rpms up or down by applying 12v + or -, and one last wire that provides 3amp 12+ to switch on something once all conditions are met (park brake on, no foot on the throttle or brake, etc). In my case I will use it to trigger (probably need a relay) my compressor clutch.

I plugged it in and stabbed the wires into a power port to grab 12v+ and everything seems to work just fine, so that is one less thing to worry about. I was surprised how easy it was and how well it worked.

I am trying to figure out how to wire the pressure switch in as rpm 2 so it will bump to the higher RPM when the pressure is low, without it wanting to fire everything up if I just happen to put it in park and hit the park brake. If rpm 1 switch is wired to a keyed 12v source, and rpm 2 switch gets its 12 source downstream of rpm 1 switch it seems like it would do the trick. That way the pressure switch would not be in play once the main switch was turned off.