F 150 Heritage 4WD Pickup V8-5.4L CNG VIN M (2004)
THE GLASS AND WILL REQUIRE DIAGNOSIS WITH A VOLTMETER OR 12V TEST LAMP AS EXPLAINED IN THIS ARTICLE.
Examples Of Non-Warrantable Grid Line Damage
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Ice scraper damage to grid lines
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Animal scratches on grid lines
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Window tint film/removal of the film which damages grid lines
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Stickers placed over grids which upon removal, removes the grid line material
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License plate (steel type placed against the inside of back glass) which rubs on the grid line causing damage
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Temporary license plate (paper stuck on to the inside of the back glass) which upon removal removes grid line material
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Cargo or lumber rubbing against the glass which removes grid line material
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Cellular phone antenna installation/removal which damages grid line material
NOTE
AN UNDAMAGED GRIDLINE WILL HAVE SMALL RIDGES THAT PROJECT ABOVE THE SURFACE OF THE GLASS AND CAN
EASILY BE FELT WHEN RUNNING A FINGERNAIL ACROSS THEM.
GRIDLINES THAT HAVE BEEN "RAZOR BLADED" WILL FEEL SMOOTH WHEN A FINGERNAIL IS DRAGGED ACROSS THE AFFECTED
AREA. THERE MAY BE SOME RESIDUE LEFT ON THE GLASS THAT APPEARS TO BE GRID MATERIAL BUT A CHECK WITH A
VOLTMETER OR 12V TEST LAMP, AS EXPLAINED IN THIS ARTICLE, WILL CONFIRM AN OPEN CIRCUIT.
GRID LINE INOPERATIVE - DIAGNOSTICS
1.
Reference Workshop Manual Section 501-11 and the Wiring Diagram Section 56 to verify power and ground to the back-glass.
2.
Connect a test lamp or DVOM to a good body ground.
3.
Turn the ignition key to the run position and depress and release the rear defroster button to turn the system on. THE GRID IS ENERGIZED FOR
APPROXIMATELY 10 MINUTES EACH TIME THE DEFROSTER BUTTON IS PRESSED.
4.
Starting from the top grid line at the center of the back-glass, touch the test lamp or DVOM + lead to each grid line. (Use caution not to damage
grid lines). The DVOM should read approximately 1/2 of the battery voltage on each line at the center of the back-glass. If using a test light, the
bulb should be approximately the same brightness on each line from top to bottom. If the DVOM or light indicates a high voltage or no voltage on
any grid line, move along the concern grid line with the + test lead or test lamp until the voltage changes suddenly. This is the area of concern, use
chalk to mark the area of concern and mark the outside of the glass at that same area.
5.
Repair per the Grid Line Repair Procedure.
GRID LINE REPAIR PROCEDURE
NOTE
LONG GAPS ARE ALMOST ALWAYS DUE TO DAMAGE AND ARE NOT WARRANTABLE, HOWEVER THEY CAN BE REPAIRED.
THE LONGER THE GAP THE MORE IMPORTANT IT IS TO APPLY A MINIMUM SIX (6) COATS OF CONDUCTIVE REPAIR
MATERIAL WITH THE FIVE (5) MINUTE DRY TIME BETWEEN EACH COAT. APPLYING LESS COATS OR NOT ALLOWING DRY
TIME BETWEEN COATS WILL PRODUCE REPAIRED RESISTANCE THAT IS GREATER THAN OEM RESISTANCE, RESULTING IN
POOR DEFROST PERFORMANCE AND EXCESSIVE LOCALIZED HEATING. REPAIRED LONG GAPS ARE GENERALLY NOT
VISUALLY PLEASING UNLESS EXTREME CARE IS TAKEN WHEN TAPING AFFECTED GRID LINE AREAS.
NOTE
IF THE BROWN COLOR UNDER THE GRID LINE IS DAMAGED OR MISSING (THIS IS VERY RARE), IT WILL BE NECESSARY TO
APPLY BROWN ACRYLIC LACQUER TOUCH-UP PAINT FOR COLOR MATCH. THIS PAINT MUST MEET SPECIFICATION
ESR-M2P100-C AND SHOULD BE APPLIED TO THE GLASS PRIOR TO APPLYING THE REAR WINDOW DEFROSTER REPAIR
COMPOUND.
