I studied what was available online about both the MAX AC and the COLD RUSH.
https://www.dieselsite.com/maxacassi...4-200373l.aspx
https://www.dieselsite.com/maxacassi...4-200373l.aspx
This is an install for a MAX AC on an older Ford 7.3 Truck. The installation is for a vacuum solenoid-controlled heater coolant flap valve. The vacuum control is the same (WHITE) vacuum signal as the recirculation air door.
When in MAX A/C (with recirculation) then also Close off the coolant to the heater core.
I must note that this will not affect any kind of NON A/C operation such as VENT. If everything is working in the Climate Control System, then you are going to be getting full coolant flow all the time except when you are in MAX A/C and the Recirculation kicks in (with a VACUUM Signal).
I people are too hot with a V10/7.3 in VENT mode then there is too much heat entering the dash through the heater core.
At this point, the COLD RUSH can be added to override the signal to the Coolant valve Solenoid so that the heater core floor can be blocked on demand.
At this point how well this works will be largely up to the operator of the switch to control the coolant flow.
If the cab is still too hot it is probably air leaking in from the dog house or other points of entry.
I should mention that there is a simple solution that is even better. This is a mechanical control valve. While this can also be controlled on demand, it can also be set to any opening positon fo the flap valve.
This is what I have used to block flow to a rear AC/heater system in my 1997 E-350.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
The only thing that is missing in the dash controls is an independent control of Recirculation. To do this would be fairly simple by adding a vacuum solenoid valve to override the normally OUTSIDE air path with a vacuum signal to the OUTSIDE/RECIRCULATE vacuum motor.
Alternatively, if you find yourself passing a road-kill skunk or a dusty section of road, you just turn your Climate Control to OFF and the outside door will close without any modifications required.