1.Is the switch light coming on when you push the button( if not could be a bcm problem)
If yes the relay should be turning on(Located in fuse box under the hood along with the 40 amp RDFG fuse)
locate relay and have a buddy push the button - do you feel the relay come on.
If no replace relay
if yes 2.Check to see if you have 12 v at the rear defroster
remove both connector and check for voltage to ground(use a 12v test light or a multimeter.)one connector should have 12v if not check fuse
If the dfrost switch light is on and the relay is good you should be able to put the test light between the 2 connectors for the rear defroster AND IT SHOULD LIGHT UP.
if it lights up theres something wrong with the defroster on the glass ,probably damaged a connector cleaning the rear glass.
Take a good look maybe the connector just came off.
Heres some info
Rear Window Defogger Operation
Battery positive voltage is supplied through the RR DEFOG fuse, in the underhood fuse block, to the REAR DEFOG relay switched input. Ground for the REAR DEFOG relay is provided by G101. The BCM supplies 12 volts on the rear window defogger switch signal circuit to the HVAC control assembly. When you depress the rear window defogger switch, the rear window defogger switch pulls the signal circuit low. The BCM interprets as a request for the rear window defogger system. The BCM enables the rear window defogger system by supplying voltage to the REAR DEFOG relay coil. The relay coil supply voltage is also spliced off internally in the BCM to the supply voltage circuit of the rear window defogger indicator. The REAR DEFOG relay is energized and the rear window defogger indicator is illuminated. With the relay energized, battery positive voltage is allowed 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 grid is provided by G403.
When you start the engine and press the rear window defogger switch for the first time, the defogger cycle lasts for 15 minutes. Further operation results in 7.5 minute defogger cycles. The rear defogger feature will not time out if vehicle speed is above 80 km/h (50 mph). The defogger cycle resets to 15 minutes when you cycle the ignition to the OFF position and then to the ON position.
2006 Cobalt SS Super Charged
Last edited by Coblasts; 01-23-2011 at 11:19 PM.