22
Genuine OEM Parts 1.800.233.4823 www.morganolsonparts.com
23
USPS 2 Ton Delivery Vehicle 2016 - 2018 Models
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No air flow, blower does not operate
POSSIBLE CAUSE #1
~ Faulty Blower Motor
CORRECTIVE ACTION
~ With ignition turned ON, unplug the 2-pin connector at the blower motor. Check the orange
wire for +12 volts and the white wire for a fully grounded circuit. If power is present and the circuit grounded, remove the
motor and wheel from the blower housing. Inspect for any evidence of entrapped debris or a broken blower wheel that
might have prevented rotation. If no such evidence exists, replace the blower motor.
POSSIBLE CAUSE #2
~ Blown fuse due to short in wire harness
CORRECTIVE ACTION
~ Refer to the
HVAC Wiring Diagram
and the Chassis Manufacturer’s wiring information.
Trace the entire HVAC wiring for an electrical short. Replace or repair as required.
POSSIBLE CAUSE #3
~ Defective Blower Switch
CORRECTIVE ACTION
~
Refer to the
Blower Switch
Continuity Diagram
and
check the blower switch for
continuity through the switch
in all four switch positions.
Replace the blower switch as
required.
,
Blower operates, but not in all blower switch settings
POSSIBLE CAUSE #1
~ Blower resistor failure.
CORRECTIVE ACTION
~ If the blower operates only on the highest blower speed (blower switch rotated fully clock-
wise), the blower resistor has, most likely, failed. [Hint: The resistor is bypassed when the highest blower speed is select-
ed.] Refer to the
Blower Motor Resistor
-wire connector from the resistor. Check
for electrical continuity between terminal 1 and 2. If an open circuit exists between 1 and 2, the thermal limiter has blown
and it will be necessary to replace the resistor. [Note: A failed resistor is often the results of a problem with the blower
motor. Make sure that the blower motor is fully operable and is not bound in any sort of way by a broken blower wheel
or entrapped debris within the blower housing.]
POSSIBLE CAUSE #2
~ High-blower relay failure
CORRECTIVE ACTION
~ If the blower operates in all speed selections except for the highest selection there is a possi-
bility that the high-blower relay has failed. [Note: The high-blower relay is activated when the highest blower speed is
selected. The relay extends the life of the blower switch and insures the highest voltage for the motor.] Remove the re-
lay and test for an open circuit across terminals 85 and 86. If the circuit is open, replace the relay.
~
Air does not flow from the selected outlets
POSSIBLE CAUSE #1
~ Plenum directional doors obstructed
CORRECTIVE ACTION
~ Examine the air distribution Plenum for any possible obstruction that might have become en-
trapped internally. Refer to the
Mode Selection & Servo Motor Position Correlation Diagram
for the position of each
of the doors in every mode selection. The output shafts of the servo motors can be observed, externally, as they move
through their approximate 100 degrees of travel. Also, the doors can be physically touched by removing the 5” flexible
inlet duct and reaching into the plenum’s air intake. If a physical obstruction is suspected, it may be necessary to re-
move the plenum. [Note: Access to the plenum’s mounting hardware will require removal of the defroster ducts from
atop the dash.]
