No more defog on both side mirrors

Fuse box rear , fuse #23 30 amp ! Do you know where this is located ? There is also a relay for the Rear window defogger , located in the same rear fuse box .
Fuse Block - Rear
Left side of the luggage compartment, behind the left rear wheel well . But you really need to know how it works , you can check fuse an relay .
Rear Window Defogger Operation
Battery positive voltage is supplied through the BATT 1 fuse in the underhood fuse block to the rear defog relay switched input. When the rear defog switch button is pressed, the body control module (BCM) energizes the rear defog relay by providing a B+ to the control circuit of the rear defog relay. This 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. The HVAC control module houses the rear defog switch and also illuminates the rear defog indicator on the switch button, upon this request. Ground for the rear window defogger grid is provided by G301 for the Sedan or G302 For the Extended Sedan.

Rear Window Defogger System Components
The rear window defogger system consist of the following components:
• HVAC control module
• Body control module (BCM)
• DEFOG relay
• Rear window defogger grid
Rear Window Defogger Operation
When you turn the ignition to the ON position, ignition voltage is supplied to the DEFOG relay coil. Battery positive voltage is supplied at all times to the DEFOG relay switched input. When the rear window defogger switch is depressed, the HVAC control module illuminates the rear window defogger indicator and sends a class 2 message to the BCM. The BCM energizes the DEFOG relay by grounding the control circuit of the relay. This allows battery positive voltage from the relay switched input through the switch contacts and out the relay switched output to the rear window defogger. Ground for the rear window defogger is provided by G306 or G390 (crew cab).
When you turn ON the ignition and press the rear window defogger switch for the first time, the defogger cycle lasts 10 minutes. Further operation results in 5 minute defogger cycles.

Do you know what your messing with ? What's the problem ?

Switch, fuse or maybe the wiring to the window has come loose or off, happens alot, kits are available at local auto parts stores...
I hope that helps...

Could have a DDS an PDS .depends on what RPO code yours has >
Outside Mirror Description and Operation (with RPO DL3)
Or
Outside Mirror Description and Operation (without RPO DL3)
Without
Heated Outside Rearview Mirror Operation
The REAR DEFOG relay controls the operation of the heated outside rearview mirrors. When rear window defogging is requested, the REAR DEFOG relay is energized and B+ is applied to the supply voltage circuit of the mirror heater element, located in the mirror face. A constant ground is also applied to the mirror face. Current will pass through the mirror heater element, warming the mirror, so long as the rear window defogger is commanded ON.

With
Heated Outside Rearview Mirror
The DDS and PDS control the activation of the mirror heaters. Upon receiving a serial data message indicating a request for heated mirrors, the DDS and PDS, will apply voltage to the mirror heater element supply voltage circuit. The mirror heaters will remain active until a new message is received indicating rear defogger is to be deactivated.
The power mirror system consists of the following components:
• Driver Door Switch (DDS)--An electronic control module with integrated switches and requires programming when replaced
• Passenger Door Switch (PDS)--An electronic control module with integrated switches, requires programming when replaced
• Power Mirror Direction Switch--Integrated into DDS and is a four position momentary switch that provides a signal input to the DDS for up, down, left/extend and right/retract with a mirror switch activation
• Mirror Select Switch--Integrated into DDS and is a three position switch that allows the operator to select the left or right mirror and also a neutral/fold position
• Mirror Extend/Retract Switch--Integrated into DDS and is a two position switch that allows the operator to select the mirror extend or mirror retract position
• Left Outside Power Mirror--Contains both the vertical and horizontal mirror motors
• Right Outside Power Mirror--Contains both the vertical and horizontal mirror motors
• Body Control Module--An electronic control module that requires programming when replaced, serves as the power mode master and is the main message handler
• Horizontal and Vertical Position Sensors, if equipped with memory mirrors--Supplied a 5-volt and low reference by the DDS/PDS and provide a variable voltage signal to the DDS/PDS that is proportional to mirror position
• Folding Mirror Motor, in each of the outside mirrors, if equipped with power fold mirrors--Provides extend and retract movements of the mirror and is serviced as a complete mirror assembly
Your best bet mite be to take to a qualified repair shop , i really don't think you'll be able to do anything with it.
Do you have wiring diagrams so you know which wires to test ,do you know how to do electrical testing ?
The Driver Door Switch (DDS) and Passenger Door Switch (PDS) supply voltage to the outside rearview mirror heater elements upon receipt of a serial data message from the HVAC module indicating that the rear defrost system is active. The door switch supplies B+ through the driver/passenger mirror heating element supply voltage circuit when a request is seen. Ground is applied through the driver/passenger mirror heating low reference circuit.

check the connector in the door,might have come apart from slamming the door,ro the element no longer working to defrost

Rear defrost/defog is electric.Rigger says check the fuses and put the proper amp fuse in.Check owners manual for fusebox position forr rear defog.

I have a 2001 impala so this may or may not help but the rear defog relay is on the passenger side dash next to the door Also the rear defog breaker is in the same place.

could be a blown fuse. Take it into the dealership.. it's probably still under warranty!

On each side of the Window (Could be at top or Bottom0 There are Small Slide on Wiring Connectors. Sometimes these Get Loose. I would start There.

the only place to get another switch is the dealer or the junkyard. why are you changing switch? there is a service bulletin on poss. problems with the defrost grid in rear window. bulletin number is 04-08-48-001b call dealer for details