Owner`s manual

OPERATION — PAGE 14
WILLIS POWER SYSTEMS
Extreme Cold Weather System
The standard system is integrated into the truck engine’s coolant
ow to keep the truck engine warm at all times. Included in the
standard system is a valve assembly that uses the coolant ow to
produce maximum heat in cold temperatures.
Below are the instructions on how to use the valve system when you
are running the A/C or the heat. Please follow these directions in
order for your system to operate properly.
For Heat
1. Both parallel valves on the evaporator side must be open.
2. The cross valve between the two coolant lines must be closed.
This allows the hot coolant to ow into the heater core of the evapo-
rator, and then back out to the APU.
See image below: