Riviera V6-3.8L SC VIN 1 (1995)
Rear Defogger: Technical Service Bulletins
A/C - Broken Rear Window Defogger Grid Detection
Bulletin No.: 04-08-48-001B
Date: June 28, 2005
Rear Window Defogger - Broken Heating Grid Detection Method
2006 and Prior Passenger Cars and Light Duty Trucks (Including Saturn)
2003-2006 HUMMER H2
2006 HUMMER H3
This bulletin is being revised to add the 2006 model year and additional models. Please discard Corporate Bulletin Number 04-08-48-001A (Section 08 -
Body and Accessories).
The addition of vertical grid lines to the heated back window defogger circuits has made it difficult to detect broken defogger grid lines. In the past, it
was a simple matter to use a voltmeter to check the continuity of each grid line in order to locate a non-functional line. Some new design back windows
have two vertical grid lines that connect all of the horizontal grid lines together, thereby providing alternate routes for the electrical current to follow.
This makes the old test method ineffective. If the vehicle does not have the vertical lines, the old (line-by-line) test methods can be used.
Permatex(R) Quick Grid, GM P/N 12346001, or equivalent
A small ball of fine steel wool Type 00, or
Optional - A strip of liquid crystal heat sensitive paper, 51 mm x 305 mm (2 in x 12 in) or similar size (Contact Edmund Scientific at 800-728-6999
for part number CR30723-70 or go to www.scientificsonline.com), or
Optional-A portable infrared thermometer, GE-46819, available from Kent-Moore (1-800-345-2233), or equivalent.
There are three distinct zones across the back window that must be checked. They are:
the driver's side outboard of the two vertical lines
the passenger side outboard of the two vertical lines
the central zone that falls between the two vertical lines
To detect a broken grid line in any of the above three zones and to isolate the exact location of the break, perform the following steps:
Approved safety glasses and gloves should be worn when performing this procedure to reduce the chance of personal injury.
Cover the rear shelf area to prevent damage to the interior trim material.
Start the engine and turn on the back window defogger.
Take the ball of fine steel wool and twist one end to a point. Move the point slowly across each grid line. Be sure to start at the far side of the zone
and move it to the opposite side of the zone. When you bridge the grid line break with the steel wool, you will see a small spark. Repeat the test
over the same area to be sure you have accurately located the break. Mark the exact location of the grid line break. Repeat this portion of the test
for each grid line. If you do not see a spark at any point, it is possible that there are two breaks in the same line and zone. Close visual inspection
using a magnifying glass may be the only way to locate breaks in this case.
The following are provided as an alternative way to detect a non-functional grid line. If available, use in addition to the steel wool.
Method using liquid crystal heat sensitive paper: