Blower Will Not Operate or Operates at Reduced Speed
Test
No.
Test
Test Procedure
Test Result
Action
5
Check voltage drop.
Remove the blower motor from
the HVAC housing.
Turn ignition on, set blower
speed to high.
Check voltage on the power and
ground circuits by back-probing
the blower motor connector.
Check between the positive and
negative battery posts.
NOTE: High voltage drop may
cause the blower motor to enter
voltage protection mode. This will
cause the blower to operate at
reduced speed and, if severe
enough, may stop the blower
altogether.
Less than 0.2V
Go to test no. 6
.
More than 0.2V
Locate source of high resistance
causing voltage drop. Repair as
necessary then
go to test no. 7
.
6
Does the blower
motor operate at all?
—
Yes
Check if blower motor feels hot
and make sure there are no
obstructions to airflow. If no
obstructed airflow or blower feels
hot, replace blower motor then
go
to test no. 7
.
No
Replace blower motor, then
go
to test no. 7
.
7
Verify repair.
Verify that repair resolved the
problem.
Problem resolved
Done
Problem unresolved
Repeat test no. 1
.
Table 12, Blower Will Not Operate or Operates at Reduced Speed
Diagnosis for Blower Speed is Not Available
Test
No.
Test
Test Procedure
Test Result
Action
1
Does blower operate
at all?
—
Yes
Go to test no. 2
.
No
Perform the tests in
2
Check feedback
speed/diagnostic
circuit.
Check for open or short circuit in
blower motor feedback speed/
diagnostic circuit between the
blower motor and the FCU/ACU.
Circuit is open or
shorted
Repair blower motor feedback
speed/diagnostic circuit then,
go
to test no. 3
.
Circuit okay
Perform the tests in
3
Verify repair.
Verify that repair resolved the
problem.
Problem resolved
Done
Problem unresolved
Repeat test no. 1
.
Table 13, Diagnosis for Blower Speed is Not Available
Heater and Air Conditioner Troubleshooting
83.00
Symptom Driven Diagnosis
122SD and Coronado Workshop Manual, Supplement 9, June 2014
350/26