Hvac Main Blower Inoperative All But High; Hvac Compressor Inoperative - Hummer H1 Service Manual

Section 12 Electrical System
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Step
1 Ignition on, blower switch set to Med2, mode dial
set to face. Measure voltage on the yellow
wire(CKT754) at the blower relay. Is voltage
present?
2 Ignition on, blower switch set to Med2, mode dial
set to face. Measure voltage on the grey
wire(CKT752) at the blower resistor. Is voltage
present?
3 Ignition on, blower switch set to Med2, mode dial
set to face. Measure voltage on the grey
wire(CKT752) at pin C of the 8pin connector on
the back of the HVAC control head. Is voltage
present?
Step
1 Perform On-board diagnostic system check. Is
system functioning properly?
2 Does A/C system have an adequate charge?
3 Is engine in an overheated condition?
4 Connect scan tool to vehicle. Ignition on, find
misc. tests and command compressor clutch on.
Does clutch come on?
5 Disconnect the compressor clutch. Connect a test
lamp to ground, and probe the brown wire at the
clutch connector. Using the scan tool, command
the clutch on. Does the test light come on?
6 Remove A/C relay from the exterior fuse box.
Using a DVOM set to measure voltage, ignition
on, check for voltage at cavities 4E and 6E
(CKT400) in the exterior fuse box. Is voltage
present?
05745159

HVAC Main Blower Inoperative ALL BUT High

Action

HVAC Compressor Inoperative

Action
Electrical System
Value(s) Yes
8 -10v Replace the
blower relay.
12v Replace blower
resistor.
12v Repair open,
bad connection
or short to
ground in CKTS
751, 752, and
755 between
HVAC control
head and resis-
tor block.
Value(s) Yes
Go to step 2.
Go to step 3.
Cool down and
recheck.
Go to step 10.
Replace the
compressor
clutch.
12v Go to step 7.
12-75
No
Go to step 2.
Go to step 3.
Replace control
head.
No
Diagnose prob-
lem in on-board
diagnostic sys-
tem first.
Diagnose leak
and recharge.
Go to step 4.
Go to step 5.
Go to step 6.
Repair open,
bad connection
or short in
CKT400
between exte-
rior fuse box
and ignition
switch.
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