Electrical Systems - Chassis
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
9•238
Diagnosis of Electric Water Valve:
Theory of Operation: Monaco Coach models with a center dial temperature
control use a potentiometer at the control head for input of desired tempera-
ture. The water valve which controls the water flow to the heater core is
opened and closed by a stepper motor mounted on the water valve. A control
module compares the output voltage from the control to that of the feedback
for the stepper motor of water valve. The control module then drives the motor
to within one-half volt of the control potentiometer voltage.
Functional Test:
• Start and operate the engine until the water reaches normal operating
temperature.
• Set the HVAC temperature control to the full hot position.
• The discharge air outlets should have hot air.
• Rotate the temperature control to full cold position.
• Allow 10 minutes for the temperature to stabilize.
• The discharge air outlets should have cold air.
No Heat:
• Check the blower and air mode operations. Fix or repair prior to
proceeding.
• Verify the engine is reaching normal operating temperature. (Check with
engine manufacturer for proper procedure.)
• Check the inlet hose at the water valve. The hose has hot water at the
valve inlet. The inlet water temperature should be the same as the engine
water temp.
• With the temp control on full hot position, check the outlet hose of the
water valve. The hose should be at engine water temperature.
Vacuum Generator:
The vacuum generator is important to the operation of the dash heating
and A/C systems. This provides the vacuum to open and close the vacuum
switches. When the vacuum generator is operating it creates 15 inches of
vacuum and is passed to a reservoir ball. Most dash heater and A/C systems
will only require 10 inches of vacuum to operate the switches. The output from
the reservoir is sent to the vent control knob. The control knob will then direct
the vacuum operation to the appropriate vacuum switch to open or close vents
and switches. The vacuum generator uses the air from the front air storage tank
through a 1/4 inch red air line. Whenever the ignition is ON and the A/C is
operating the vacuum generator will operate.
WINDSOR