Rear Defroster affects Radio

[TamedTaz]

1998 Pontiac Grand Prix GT Now that it is cold and I use the rear defroster, only when the defroster is on the radio seams to loose the signal its like you unpluged the atenna only a few local stations come in fuzzy as soon as I turn off the defroster the radio is fine. What gives?

[troy1]

there is a TSB on this some where out there.

[phaelax]

same thing on my '99 and '00 gtp

[mike561]

I know the radio antenna runs across the back glass just like the window defogger does (if you diddnt know that already) but im not sure what could be wrong though.

[richtazz]

The GM parts computer shows no service bulletin, but that doesn't mean there isn't one. IF Bnaylor or GMMerlin reads this, they may be able to come with something.

[BNaylor]

Originally Posted by richtazz

The GM parts computer shows no service bulletin, but that doesn't mean there isn't one. IF Bnaylor or GMMerlin reads this, they may be able to come with something.

I am not aware of a TSB on any defogger problem on a GrandPrix, however, I am aware that certain GM cars like "N" bodies have a similar problem. There is supposed to be a "black box module" where the defogger line and radio antenna line input and then split to their respective components like the radio and the defogger relay. It's supposed to be located on the rear passenger side pillar underneath the plastic trim. If you look carefully you'll see the electrical plugs for the window heater element.

The static sound or signal loss is probably a short to ground being picked up by the radio signal coaxial. Also, it's important to make sure none of the two grids are damaged on the rear window.

For example, the module on Aleros had fried/burnt electrical contacts. Replacement of the module or repair of damaged radio coaxial cable corrected the static problem and/or malfunctioning defogger.

Maybe Rich can come up with a part number.

The Alero module is part number 22618677 ($110.00 GM List?) but I'm not sure if matches the one supposedly in the Grand Prix.









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[troy1]

its TSB # 03-08-44-005C
Section 08 Body & Accesories
Date Jan 05

Sorry I cant post it file is to large

[BNaylor]

Originally Posted by troy1

its TSB # 03-08-44-005C
Section 08 Body & Accesories
Date Jan 05

Sorry I cant post it file is to large

Document ID# 1583196 2004 Cadillac CTS Poor Radio Reception or Radio Static/Increased Interference with Rear Window Defogger On or Some Rear Window Defogger Grids may be Inoperative (Diagnose and Repair Rear Window Defogger Heating Grid) #03-08-44-005C - (Jan 19, 2005)Poor Radio Reception or Radio Static/Increased Interference with Rear Window Defogger On or Some Rear Window Defogger Grids May Be Inoperative (Diagnose and Repair Rear Window Defogger Heating Grid) 1997-2005 Buick Century, LeSabre, Park Avenue, Regal1997-2001 Cadillac Catera1997-2002 Cadillac Eldorado1997-2004 Cadillac Seville1997-2005 Cadillac DeVille2003-2005 Cadillac CTS1997-2005 Chevrolet Corvette2000-2005 Chevrolet Impala, Monte Carlo2004-2005 Chevrolet Epica, Malibu1997-2003 Oldsmobile Aurora<- BackForward ->Print
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Service Information1998-2002 Oldsmobile Intrigue1999-2004 Oldsmobile Alero1997-2005 Pontiac Grand Am, Grand Prix2004-2005 Pontiac GTOThis bulletin is being revised to add the 2005 model year and update the part number information for Permatex Quick Grid. Please discard Corporate Bulletin Number 03-08-44-005B (Section 08 -- Body and Accessories).ConditionSome customers may comment that the radio has poor reception or radio static/increased interference when the rear window defogger is turned on. Also, some rear window defogger grids may be inoperative.CauseThis condition may be due to microscopic cracks in the electrically heated grids of the rear window defogger. These cracks may cause electrical interference when the rear defogger is on and this could affect radio reception.BackgroundThe 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. 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.Materials Required• Permatex 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
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Service Information• Optional -- A portable infrared thermometer, GE-46819, available from Kent-Moore (1-800-345-2233), or equivalent. CorrectionThere 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:Caution: • 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. 1. Start the engine and turn on the back window defogger. Important: The first place to check should be the driver side segment 2 to 3 lines up from the bottom about 380-385 mm (15-15.2 in) from the buss bar.2. 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. 3. The following are provided as a alternative way to detect a non-functional grid line. If available, use in addition to the steel wool. A. Method using liquid crystal heat sensitive paper.
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Service InformationImportant: The first part of the test must be completed quickly before the entire surface of the back window becomes warm. i. From outside the vehicle, place the heat sensitive paper (dull surface in contact with the glass) against the top driver side grid line. Start the engine and turn on the back window defogger. A distinct color change will take place at each conductive grid line. Repeat for the bottom grid lines until they have all been checked in the driver side zone. ii. Repeat the process for the passenger side and center area zones. iii. If no color change is noted for a grid line, place a crayon or china marker check mark beside it. Mark each grid line in the zone where it is non-conductive and therefore not heating up. More than one broken grid line may be found. B. Method using a portable infrared thermometer. i. Start the engine and turn on the rear back window defogger. ii. From inside the vehicle, start at the top driver side grid line and slowly run the portable infrared thermometer vertically down the rear window contacting each grid line. You should be able to see a district variation in temperature readings. iii. Mark each grid line in the zone where it is non-conductive and, therefore, not heating up. More than one broken grid line may be found. iv. Repeat the process for the passenger side and center area zones. 4. Use Permatex Quick Grid, GM P/N 12346001, or equivalent, to repair each broken grid line. Follow the manufacturer's instructions. 5. Wait 24 hours before turning the defogger on, or the repair can be fast cured using a heat gun, 260°C -- 371°C (500°F -- 700°F). Hold the heat gun within 25 - 51 mm (1- 2 in) from the repair point for 2 to 3 minutes. 6. Recheck the grid line with the heat sensitive paper or a portable infrared thermometer to ensure that the line is now functional and that the repair was successful. Warranty InformationFor vehicles repaired under warranty, use:Labor OperationDescriptionLabor TimeC0631Grid, Electric Back Window Defogger -- Repair0.3 hrAddTo Repair Each Additional Grid0.1 hrAddDiagnosis Time0-0.3 hr
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Service InformationGM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION© Copyright General Motors Corporation. All Rights Reserved. Document ID# 1583196 2004 Cadillac CTS <- BackForward ->Print

[richtazz]

The GM part number is 16213462, and it is located just above the rear window, by where the passenger side c-pillar meets the roof. GM dealer retail is $88.52. I knew Bnaylor would come through with the info for you. OF course, he returned the favor of me putting him on the spot, but I came through too.

[vamc]

I will have to agree with bnaylor3400 on this. I have looked this up as well and found this to be true. I also had this happen to me. Like i said, i got Bob's back. becides, there is nothing else it could be.

[TamedTaz]

I am going to my friends house next weak he has a 99 GTP and trying see he will let me switch the black box on the c pillar and see what happens I will let you know how I make out Thanks for the info.

[vamc]

Not a problem.

['97ventureowner]

Closed. In the future please put a closing date on any polls so that they don't remain open indefinitely and get resurrected every so often by people discovering it and then voting in it.