Hi:

Thanks for the reply. Yes the Ford does have Air Brakes. Currently I empty the air tanks daily. The system only seems to get moisture during cold weather operation.

The manual for the dryer indicate that the AD-IP dryer does a purge of contaminants when the compressor starts. Here is a quote from the manual:

"PURGE CYCLE
As air brake system pressure reaches the cutout setting of
the governor, the governor unloads the compressor (air
compression is stopped) and the purge cycle of the air dryer
begins. When the governor unloads the compressor, it
pressurizes the compressor unloader mechanism and the
line connecting the governor unloader port to the AD-IP ™ air
dryer end cover control port. The purge piston moves in
response to air pressure causing the purge valve to open to
the atmosphere and the turbo cutoff valve to close off the
supply of air from the compressor (this will be further
discussed in the Turbo Cutoff Feature section). Water and
contaminants in the end cover sump are expelled
immediately when the purge valve opens. Also, air which
was flowing through the desiccant cartridge changes direction
and begins to flow toward the open purge valve. Liquid oil
and solid contaminants collected by the oil separator are
removed by air flowing from the purge volume through the
desiccant drying bed to the open purge valve."

As you can see there is no mention of a need for the heater in the above. Later on the manual describes how to test the heater but no mention of why or when to use it.

Thanks for the info.
PaMnd