Hummer H1 (2002+). Manual - part 213

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Electrical System 12-77

05745159

Ignition on, mode dial set to MAX A/C. Discon-
nect the high pressure cutout switch on the com-
pressor. Using a DVOM set to measure voltage,
check for voltage on the tan wire(CKT198). Is
voltage present?

12v

Go to step 15.

Repair open,

bad connection,

or short in

CKT198

between tem-

perature cutout

switch and high

pressure cutout

switch.

Using a DVOM set to measure resistance, check
continuity across the two pins on the high pres-
sure cutout switch. Is resistance below specifica-
tion?

<.2

Ω

Go to step 16.

Replace the

high pressure

cutout switch.

Ambient temperature above 45°. Disconnect the
ambient temperature switch. Using a DVOM set
to measure resistance, measure continuity across
the ambient temperature switch terminals. Is
resistance below specification?

<.2

Ω

Go to step 17.

Replace ambi-

ent temperature

switch.

Disconnect low pressure cutout switch. Using a
DVOM set to measure resistance, measure conti-
nuity across the low pressure cutout switch. Is
resistance below specification?

<.2

Ω

Repair open,

bad connection

or short in

CKT439

between high

pressure cutoff

switch and

PCM.

Replace the low

pressure cutout

switch.

HVAC Temperature Door Inoperative

Step

Action

Value(s)

Yes

With the ignition switch in the run position, oper-
ate temperature control dial and observe the
motor. Does door move?

Condition is
intermittent.

Go to step 2.

Remove the temperature blend door motor from
the side of the HVAC case. With the ignition
switch in the run position, operate the temperature
control dial and observe the motor. Is the motor
turning?

Mechanical

problem in the

HVAC case.

Go to step 4.

Disconnect electrical connector from the temper-
ature blend door motor. Using a DVOM set to
measure voltage, and using J–35616-92 test
adapters, probe the GN wire (CKT 399) with the
positive lead and the BK wire (CKT 58) with the
negative lead. Turn the ignition switch to the run
position. Is voltage present?

12v

Go to step 6.

Go to step 4.

HVAC Compressor Inoperative (Continued)

Step

Action

Value(s)

Yes

4-1-00

12-78

Electrical System

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With ignition on, using a DVOM set to measure
voltage and using J–35616-92 test adapters probe
the GN wire (CKT 399) with the positive lead.
Place the negative lead on a known good ground.
Is voltage present?

12v

Go to step 5.

Repair open or

short to ground

between tem-

perature blend

door motor and

fuse 7C.

With the ignition off, and using a DVOM set to
measure ohms, check for resistance between the
BK wire (CKT 58) of the temperature blend door,
and a good ground. Does resistance exceed speci-
fications?

<.2

Ω

Locate open or

bad connection

between tem-

perature blend

door motor and

G4.

Go to step 6.

Using a DVOM set to read volts, the ignition
switch on the run position, and using J–35616-92
test adapters, probe the blue wire (CKT 402) with
the positive lead, and the BK wire (CKT 58) with
the negative lead. Rotate temperature control dial
on the HVAC control head from cold to hot and
back. Is voltage present at the cold setting and 0v
on the hot setting?

Cold = 12v

Hot = 0v

Cold = 12v

Replace the

temperature

blend door

motor.

Go to step 7.

Disconnect the 8 wire connector at the HVAC
control head. Using a DVOM set to measure
ohms, check resistance between pin F (CKT 402)
of the 8 wire connector and the blue wire (CKT
402) of the temperature blend door connector.
Does resistance exceed specifications?

62K

Ω

Go to step 9.

Go to step 8.

Check for open or bad connection between the
HVAC control head 8 wire connection and the
temperature blend door motor connection. Check
for loose terminals at the control head. Was a bad
connection found?

Repair or

replace harness

as necessary.

Go to step 9.

Using a DVOM set to measure voltage, probe pin
E (CKT 399) of the 8 wire connector on the
HVAC control head with the positive lead, and
pin B (CKT 58) of the three wire HVAC control
head connector with the negative lead. With igni-
tion on, is voltage present?

12v

Replace faulty
HVAC control

head.

Go to step 10.

Using a DVOM set to measure voltage, probe pin
E (CKT 399) of the HVAC control head eight
wire connector with the positive lead. Attach the
negative lead to a known good ground. With the
ignition switch in the run position, is voltage
present?

12v

Go to step 11.

Locate short or

open between

the HVAC con-

trol head and

fuse 7C.

HVAC Temperature Door Inoperative (Continued)

Step

Action

Value(s)

Yes

4-1-00

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Electrical System 12-79

05745159

Using a DVOM set to measure ohms, check resis-
tance between pin B (CKT 58) of the HVAC con-
trol head connector and a good ground. Does
resistance exceed specifications?

<.2

Ω

Replace faulty
HVAC control

head.

Locate and

repair open or

poor connec-

tion in the

ground circuit

between pin B

and G4.

HVAC Temperature Door Inoperative (Continued)

Step

Action

Value(s)

Yes

4-1-00

12-80

Electrical System

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Figure 12-94: HVAC Blower Schematic

30A FUSE
BUILT IN
HARNESS
FUSE

TO ALTERNATOR
BATTERY TERMINAL

FUSE 7C
30A
INTERIOR
FUSE BOX

HOT IN RUN
AND START

BLOWER

RESISTOR

755 DB

751 OR

752 GY

8 PIN

HVAC
CONTROL
HEAD

754 YL

364 RD

C36-A

BLOWER
RELAY

BLOWER
MOTOR

87A

371 PP

C36-B

757 LB

399 DG

C6-G1

58 BK

9-S12-060

59 BK

LOW

BLOWER

MED 1

BLOWER

MED 2

BLOWER

HIGH

BLOWER

IGN

FEED

C37

4-1-00

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