Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHRYSLER2003300M V6-3.5L VIN MREPAIR AND DIAGNOSISWINDOWS AND GLASSHEATED GLASS ELEMENTTESTING AND INSPECTIONWINDOW DEFOGGER SYSTEM CONTROL TEST
2003 Chrysler 300M V6-3.5L VIN M
Window Defogger System Control Test
2003 Chrysler 300M V6-3.5L VIN MSECTION Window Defogger System Control Test
1. Stop the engine.
2. Check the fuse supplying power to the rear glass grid relay. If the fuse is good, (Refer to ELECTRICAL/HEATED GLASS/REAR WINDOW DEFOGGER RELAY - DIAGNOSIS AND TESTING). If the fuse is open, then go to Step 3.
3. Locate the ground lug that connects the negative lead of the rear window grid to ground. Remove the screw holding the ground lug and isolate it from any vehicle ground.
4. Connect one lead of an ohmmeter to the negative ground lug of the rear window grid (with the lug still not connected to a vehicle ground), and check the resistance to a known good vehicle ground. If the ohmmeter indicates less than 10 ohms, then the rear window defogger grid is shorting to the vehicle ground, then go to Step 5. If the ohmmeter indicates more than 100 ohms of resistance, then go to Step 6.
5. Disconnect the rear window defogger grid voltage feed wire from the vehicle harness. If the ohmmeter still indicates less than 10 ohms, then the rear window defogger grid is shorting to the vehicle ground and must be replaced. If the ohmmeter indicates more than 100 ohms of resistance with the grid voltage feed wire disconnected, then go to Step 6.
6. There is a problem with the circuits that connect to the rear window defogger relay. Refer to the appropriate wiring information for circuit descriptions. Check wiring with an ohmmeter to verify proper wiring connections to the rear window defogger relay. If no problems are found, then replace the fuse and try running the system.
2. Check the fuse supplying power to the rear glass grid relay. If the fuse is good, (Refer to ELECTRICAL/HEATED GLASS/REAR WINDOW DEFOGGER RELAY - DIAGNOSIS AND TESTING). If the fuse is open, then go to Step 3.
3. Locate the ground lug that connects the negative lead of the rear window grid to ground. Remove the screw holding the ground lug and isolate it from any vehicle ground.
4. Connect one lead of an ohmmeter to the negative ground lug of the rear window grid (with the lug still not connected to a vehicle ground), and check the resistance to a known good vehicle ground. If the ohmmeter indicates less than 10 ohms, then the rear window defogger grid is shorting to the vehicle ground, then go to Step 5. If the ohmmeter indicates more than 100 ohms of resistance, then go to Step 6.
5. Disconnect the rear window defogger grid voltage feed wire from the vehicle harness. If the ohmmeter still indicates less than 10 ohms, then the rear window defogger grid is shorting to the vehicle ground and must be replaced. If the ohmmeter indicates more than 100 ohms of resistance with the grid voltage feed wire disconnected, then go to Step 6.
6. There is a problem with the circuits that connect to the rear window defogger relay. Refer to the appropriate wiring information for circuit descriptions. Check wiring with an ohmmeter to verify proper wiring connections to the rear window defogger relay. If no problems are found, then replace the fuse and try running the system.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.