rear defrost not working [Archive] - GrandAmGT.com Forum

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mjtr21
12-19-2008, 08:16 AM
okay i had one of the tabs come off the side of the window the other day and i reattached it with that kit from advance auto parts. it worked for a couple of minutes then i noticed the tab on the other side of the window came off. so i reattached that one and now my rear defroster doesnt work at all. i push the button and the indicator light comes on but it doesnt heat up. i checked the fuse and its good and switched out the relay and still nothing. what else could be the problem i am stuck now.

Pauljp
12-19-2008, 08:47 AM
It would appear that you are not having good contact at the wiring grid on the rear window.
You should have a good ground on one side and 12VDC on the other.
Since your tabs came off, I would check the second one since it was working fine after you reattached the first one.

mjtr21
12-19-2008, 09:00 AM
okay i have a multimeter. where would i put the probes then?

ltpats
12-19-2008, 09:39 AM
REAR WINDOW DEFOGGER DESCRIPTION AND OPERATION

REAR WINDOW DEFOGGER SYSTEM COMPONENTS
The rear window defogger system consist of the following components:
HVAC control assembly
RR DEFOG relay
Rear window that has a number of grid lines
REAR WINDOW DEFOGGER OPERATION
Battery positive voltage is supplied through the RR DEFOG fuse in the underhood fuse block to the RR DEFOG relay switched input. With the ignition in the ON position, ignition voltage is supplied through the HTR-A/C fuse in the underhood fuse block to the HVAC control assembly and the RR DEFOG relay coil. When you depress the rear window defogger switch, the HVAC control assembly illuminates the rear window defogger indicator and grounds the control circuit of the RR DEFOG relay. This energizes the RR DEFOG relay and allows battery positive voltage from the relay switched input through the switch contacts and out the relay switched output to the rear window defogger grid. Ground for the rear window defogger is provided by G402.

When you start the engine and press the rear window defogger switch for the first time, the defogger cycle lasts for 10 minutes . Further operation results in 5 minute defogger cycles. The defogger cycle resets to 10 minutes when you cycle the ignition to the OFF position and then back to the ON position.

DEFOGGER GRID LINES DIAGNOSIS
Start the engine.
Activate the rear window defogger system.
Connect a test lamp to a good ground.
Defogger Grid Lines Diagnosis
Move the test lamp probe along each grid line.
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.
If the test lamp goes out, test the grid line in at least 2 places to eliminate the possibility of bridging the open (2) in the grid line.
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.
Once the open is located, repair the grid line.

If the side peices are damaged (the ones that run from the top of the grid to the bottom) there is a repair kit for them.

timberwoof
12-19-2008, 09:39 AM
mine just came loose.... that sucks

blackgt2k
12-19-2008, 10:46 AM
you just have to make sure that the contact area is clean and it makes a good contact. i had the same problem. as long as your using the correct metal cement you should be fine

mjtr21
12-19-2008, 12:02 PM
well i just removed both tabs again. i am going to clean both of them with alcohol and clean area where they attach to the window too. actually does anyone know where i can get new tabs and wires? those are the only components right (tabs, wires, grid, switch, fuse and relay). the fuse and relay are good. i had the window replaced last year and tinted so i konw the grid isnt damaged. all im left with is wires and tabs. i dont think theres a module like on the aleros right? thanks for the suggestions.

ltpats
12-19-2008, 12:17 PM
well i just removed both tabs again. i am going to clean both of them with alcohol and clean area where they attach to the window too. actually does anyone know where i can get new tabs and wires? those are the only components right (tabs, wires, grid, switch, fuse and relay). the fuse and relay are good. i had the window replaced last year and tinted so i konw the grid isnt damaged. all im left with is wires and tabs. i dont think theres a module like on the aleros right? thanks for the suggestions.

BUS BAR/ANTENNA TERMINAL REPAIR



Buff the repair area with fine steel wool. This will remove the oxide coating formed during window manufacturing.
Apply paste-type rosin flux in small quantities to the rear defogger bus bar lead wire, antenna or defogger terminal repair area using a brush.
Coat the solder iron tip with solder. Use only enough heat to melt the solder and only enough solder to ensure a complete repair.
Apply solder to the bus bar. Draw the soldering iron tip across the fluxed area thinly coating bus bar with solder.
Apply a small amount of flux to the underside of the rear defogger bus bar lead wire, antenna or defogger terminal.







Apply solder to the underside of the rear defogger bus bar lead wire, antenna or defogger terminal. Draw the soldering iron tip across the fluxed area thinly coating the wire or terminal with solder.
Apply heat to the top of the rear defogger bus bar lead wire antenna and/or defogger terminal, causing the solder spot to melt and fuse together.
Use pliers to hold the rear defogger bus bar lead wire, antenna or defogger terminal.
Holding force should not be removed until the solder has solidified.
IMPORTANT: Do not overheat the terminal when soldering it to the bus bar. Soldering iron tip temperature should be just enough to melt the solder allowing the solder to run freely. The iron should be in contact with the bus bar for as short a time as possible.



Solder the wire or terminal to the bus bar.
Wipe off any excess flux.
Connect the electrical connector.

mjtr21
12-20-2008, 08:56 AM
yeah that doesnt really answer my question.

GRABER75
12-20-2008, 09:10 AM
those kits don't work..they are a quick easy fix...if I understand you correctly the tabs came off of the window...not the harness came off the tab. Same happened to me I fiddled around with the grid lines and frustrating it was..I decided to say SCREW IT! and went to my local autowreckers for a new back window...all in all it cost me about $100 bucks installed...some may think that is a bit costly but when frustration arises and you dont want to "Mickey Mouse" the problem, it was the best route for "me"to go.

mjtr21
12-20-2008, 05:17 PM
okay well i figured my problem out. there isnt any current going through my tabs because they are so messy. my brother tried soldering it a week ago when the damn thing came off. and he kinda made a mess on the tab. so when i bought that kit it said to use sandpaper on the tabs and i think that ruined them. so does anybody know where i can get new tabs?

ltpats
12-22-2008, 05:29 AM
those kits don't work..they are a quick easy fix...if I understand you correctly the tabs came off of the window...not the harness came off the tab. Same happened to me I fiddled around with the grid lines and frustrating it was..I decided to say SCREW IT! and went to my local autowreckers for a new back window...all in all it cost me about $100 bucks installed...some may think that is a bit costly but when frustration arises and you dont want to "Mickey Mouse" the problem, it was the best route for "me"to go.

4 years and working fine, if not installed correctly they wont work.

Metallman56
12-22-2008, 04:28 PM
both of my tabs have fallen off. i just took it into a glass shop. they charged me less then the kit from autozone. thats what i'd do, just take it somewhere. my guy was done in less then 10 mins. and i will probably cost less then the tabs themselfs.

GRABER75
12-22-2008, 04:58 PM
4 years and working fine, if not installed correctly they wont work.

well you must have a bit of luck on your side...didnt work in my case. lol Im not somebody who cuts corners on a project and do a half fast job on anything I do.

ltpats
12-23-2008, 08:07 AM
well you must have a bit of luck on your side...didnt work in my case. lol Im not somebody who cuts corners on a project and do a half fast job on anything I do.

Neither am I, maybe 25 years of experience had something to do with it. :D Anybody can replace parts.

gerry
01-27-2010, 11:35 AM
Hello, my rear defrost didn't work either. I searched on the net and was able to fix the problem myself. I hope this helps someone, here are the steps.First check the mini fuse under the hood. On my 2002 alero its fuse# 33. Mine was fine and the defrost light would go on but no defrosting would occur.Second you have to remove the panel on the C pillar on the passenger side. Its held on with about 5 clips so be careful not to break any. I didn't have to completely remove mine to be able to access the little black box behind this panel. This module regulates the current and also acts as an antenna for your radio. You'll have to unscrew the one nut that holds this to the frame and unplug the 4 wires. The two clips attached to the window just slide strait off but it takes some effort. Careful not to break these! The bottom co-axle antenna wire pulls right out and lastly there is the main power connector that is just clipped on. This is the problem connector.Either this module has shorted out or, as in my case, the flimsy connector shorts out. Either way, you'll need to open the module. Around the perimeter of the module are 5 or 6 holes that look like screw holes but they are not. They're glued plastic pins so you'll need to get the smallest drill bit you can find and eat away at the plastic until the two plastic pieces split apart.Inside the module is a circuit board, and two large metal prongs that the electrical connector connects to via that flimsy connector. Bypass the connector by soldering two 4 inch lengths of* wire to each of these silver prongs. (I used a thin length of green wire and a thicker black wire to match the color code of the wires in the connector) **Make sure the wire you use is the same thickness as the wire going into the connector or it will overheat and may catch on fire.** Once soldered, close up the box with a little tape or crazy glue to hold it together. Bolt the module back to the frame, reconnect the two clips to the window and the radio antenna. Now the last clip, the one that supplies the power, is cut off and you attach each of the bare wires directly to the two 4 inch wires coming out of your module. (This is why itís a good idea to maintain the same color code) Twist on a wire connector and replace the panel. Everything should work now.Inside my module there was some solder that had melted so I cleaned that up as best I could. Also, before I decided to cut off the connector, I pressed the rear defrost button and tested the voltage of the pins inside the connector and it was 12v so it was simply a matter of the pins no longer contacting the pins inside the module. You could try to bend the pins to reestablish contact but I suggest you bypass the connector all together. It shorts out and could start a fire. Good luck. Gerry