twist-lock metal jar lid. A drill template
pattern is used to locate all holes for the
purge valve, lamp mount, and screws.
The bottom of the lid carries the heat-lamp socket. The humidity sensor
capacitor is cylindrical and mounted
on the dry air delivery pipe. It is buried
in the silica gel. All electrical feeds, lid
plumbing, and mounting screws must
be airtight. This is accomplished by
soldering the brass air pipes to the top
of the lid. Use RTV silicone or Loctite
on the purge valve, wiring feeds for the
lamp, and humidity sensor. A Dremel-type grinding tool is recommended
to remove the paint from the lid top
around the brass air tube holes. This
will allow soldering of the brass air
tubes to the metal lid.
Install the long, dry-air pickup tube/
humidity sensor and its associated
airstone (dust filter). Solder the air
tubes to the lid. (A slight outboard tilt
orientation in the mounting of the
long, dry-air tube away from the lamp
is recommended.)
and injected back into the engine
crankcase. Any moisture inside the
engine vaporizes with the incoming
dry air and is moved by the constant positive pressure from the
air pump to the crankcase vent,
back to the pump and the silica
gel dryer. At some point, the silica
gel will absorb all the moisture it
can hold. At that point the process
stops and the dryer goes into the
heat/purge mode of operation to
dry out the desiccant.
How the Engine Dryer Works
The dehumidifier is connected to the
engine as soon after engine shutdown as possible—before the engine
cools. It is then run on a 24/7 basis.
A small aquarium-type air pump
forces ambient humid air drawn from
the crankcase vent through a plenum
bottle containing silica gel (this is
the stuff used in shipping and storing aircraft engines and electronics).
The silica gel has a great affinity for
moisture and literally sucks it out
of the air. The dried air is filtered
• Connect the humidity sensor
lead to the lid connection and on the
electronics PC board.
The scuba regulator diaphragm
valve and stem mount vertically in
the valve body and are connected by
a pin linkage to the lever fixed to the
modified relay armature. Some care
must be taken to position the mounting
of the vertically oriented sensor board
to assure free and smooth motion of
the valve lever mechanism. The valve
closes when the relay armature is in its
normally closed (up) position. Internal
air pressure buildup will help push the
valve closed during dryer operation.
