Hummer H2. Manual - part 695

5

1. Turn OFF the ignition.  

2. Disconnect the DEFOG relay.  

3. Turn ON the ignition, with the engine OFF.  

4. Connect a test lamp between the battery 

positive voltage circuit of the DEFOG relay 
switched input and a good ground.  

Does the test lamp illuminate?

Go to Step 6

Go to Step 7

6

1. Connect a 40 amp fused jumper between the 

battery voltage circuit of the DEFOG relay 
switched input and the relay switched output 
to the supply voltage circuit of the rear 
window defogger.  

2. Connect a test lamp between the left side of 

the rear window defogger grid and a good 
ground.  

Does the test lamp illuminate?

Go to Step 9

Go to Step 12

7

Test the battery positive voltage circuit of the 
DEFOG relay switched input for an open or high 
resistance. Refer to Circuit Testing and Wiring 
Repairs in Wiring Systems. 
Did you find and correct the condition?

Go to Step 15

Go to Step 11

8

Inspect for poor connection at the harness connector 
of the HVAC Control Module. Refer to Testing for 
Intermittent Conditions and Poor Connections 
and Connector Repairs in Wiring Systems. 
Did you find and correct the condition?

Go to Step 15

Go to Step 13

9

Inspect for poor connection at the DEFOG relay. 
Refer to Testing for Intermittent Conditions and 
Poor Connections and Connector Repairs in 
Wiring Systems. 
Did you find and correct the condition?

Go to Step 15

Go to Step 14

10

Repair an open or high resistance in the ground 
circuit of the rear window defogger. Refer to 
Wiring Repairs in Wiring Systems. 
Did you complete the repair?

Go to Step 15

-

11

Repair a short to ground in the supply voltage circuit 
of the rear window defogger. Refer to Wiring 
Repairs in Wiring Systems. 
Did you complete the repair?

Go to Step 15

-

12

Repair an open or high resistance in the supply 
circuit of the rear window defogger. Refer to 
Wiring Repairs in Wiring Systems. 

 

2004 Hummer H2 

2004 ACCESSORIES & EQUIPMENT Stationary Windows - Hummer H2

  

DEFOGGER GRID LINES DIAGNOSIS 

This test is for reference only. A grid line fault requires the rear window replacement. Refer to Rear Lift 
Window Replacement . 

1. Start the engine.  

2. Activate the rear window defogger system.  

3. Connect a test lamp to a good ground. 

Did you complete the repair?

Go to Step 15

-

13

Replace the HVAC Control Module. Refer to 
HVAC Control Module Replacement in HVAC 
Systems - Automatic. 
Did you complete the replacement?

Go to Step 15

-

14

Replace the DEFOG relay. 
Did you complete the replacement?

Go to Step 15

-

15

Operate the system in order to verify the repair. 
Did you correct the condition?

System OK

Go to Step 2

 

2004 Hummer H2 

2004 ACCESSORIES & EQUIPMENT Stationary Windows - Hummer H2

  

Fig. 4: Defogger Grid Line Zones 
Courtesy of GENERAL MOTORS CORP. 

4. Move the test lamp probe from zone 5 to zone 1 along each grid line. 

z

If the test lamp shows full brilliance at both ends of the grid lines. Inspect for an open or poor 
connection in the ground circuit of the rear window defogger grid. Refer to Testing for 
Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. 

IMPORTANT: The test lamp brilliance will decrease proportionately to the increased 

resistance in the grid line as the probe is moved from the battery positive 
bus wire to the ground bus wire. The test lamp brilliance may vary from 
one window to another.

 

2004 Hummer H2 

2004 ACCESSORIES & EQUIPMENT Stationary Windows - Hummer H2

  

Fig. 5: Testing Locations On Grid Lines 
Courtesy of GENERAL MOTORS CORP. 

z

If the test lamp goes out, test the grid line in at least 2 places (1,3) to eliminate the possibility of 
bridging the open (2) in the grid line.  

MIRRORS - AUTOMATIC DAY-NIGHT INOPERATIVE 

Mirrors - Automatic Day-Night Inoperative 

Step

Action

Value

(s)

Yes

No

Schematic Reference:Inside Rearview Mirror Schematics 
Connector End View Reference:Stationary Windows Connector End Views

1

Did you review the operation of the automatic day-
night feature of the mirrors and perform the 
necessary inspections?

-

Go to Step 2

Go to 

Symptoms - 

Stationary 

Windows

2

1. Turn ON the ignition, with the engine OFF.  

2. Turn OFF the automatic day-night feature of 

the inside rearview mirror.  

3. Observe the driver outside rearview mirror.  

Does the driver outside rearview mirror remain in a 
darken state?

-

Go to Step 20

Go to Step 3

1. Turn ON the automatic day-night feature of 

 

2004 Hummer H2 

2004 ACCESSORIES & EQUIPMENT Stationary Windows - Hummer H2