How does the fording switch work off a Humvee?

31 05 2012

All of the vent lines from the drive train and the power steering reservoir cap tee together and connect to one port on the control valve. The other two ports connect to the air filter housing and the CDR valve. The control valve switch connects the vent lines to the air filter housing in “Vent” mode and the CDR valve in “Ford” mode.

The sensor cup is also connected to the CDR valve. As the water level rises and the cup fills with water, air pressure builds in the line and exerts force on the CDR diaphragm. This causes some amount of crank case pressure to be diverted from the CDR through the line to the control valve. If the control valve is set to “Ford” and the CDR is connected to all the vent lines, all of the drive train is pressurized by the engine. As the water level in the sensor cup rises, more pressure is diverted to the drive train. This way water won’t push in through the seals when components are submerged because the pressure is equalized inside and out.




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